Dielectric ceramic compositions and dielectric resonators

FIELD OF THE INVENTION
This invention relates to dielectric ceramics and dielectric resonators for use in such high-frequency ranges as microwave and millimeter-wave frequencies.
Recently, dielectric ceramics have been widely used in dielectric resonators and filters in microwave and millimeter-wave frequencies at wavelengths of several centimeters or less (hereinafter referred to as microwave in general). It is required that a dielectric material for use in such applications have a high unloaded Q (Qu) value and dielectric constant .di-elect cons..sub.r, and that the temperature coefficient at a resonant frequency .tau..sub.f be variable as desired. The Q value is the inverse of an inductive loss tan .delta..
Various materials appropriate for use in such applications have been conventionally reported, among which ZrTiO.sub.4 ceramics are included. Also included in such materials are ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramics, the ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 --MgO ceramic suggested in Japanese Laid-Open Patent No. 62-132769 and the ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 --CoO-Nb.sub.2 O.sub.5 ceramic in Japanese Laid-Open Patent No. 2-192460, for example.
However, although the ZrTiO.sub.4 ceramics according to the prior art have a high dielectric constant of 45, the temperature coefficient at a resonant frequency is high in the positive side at 54ppm/.degree. C., and the temperature coefficient at a resonant frequency is significantly varied by the heating history during sintering. The ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramic has achieved a low temperature coefficient of about Oppm/.degree.C. at a resonant frequency, but the variation of temperature coefficient at the resonant frequency caused by the heating history causes problems. In addition, conventional materials have such problems that the dielectric constant and unloaded Q value are low, and that the temperature coefficient at a resonant frequency cannot be varied as desired. Further, in the case of application to a coaxial resonator having electrodes formed on the surface of the dielectric ceramic, a planar filter and the like, there are problems in that the resonant frequency is easily deviated and the unloaded Q value is decreased when the bond strength of the electrode layer to the dielectric ceramic is low.
SUMMARY OF THE INVENTION
The object of the present invention is to provide ZrTiO.sub.4 and ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramics with less variation of temperature coefficient at a resonant frequency due to heating history during sintering.
It is another object of the present invention to provide dielectric ceramics that have a high unloaded Q value and a high dielectric constant, and have a temperature coefficient at a resonant frequency which is variable as desired.
It is still another object of the present invention to provide dielectric resonators which comprise strong electrode layers having a high unloaded Q value. The subject of the present invention is to achieve one of these objects or to achieve more than two objects at the same time.
In order to achieve the objects described above, the present invention provides a dielectric ceramic comprising as the main component a complex oxide formed of both Zr and Ti, at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta, and as the accessory components at least one component selected from the group (C) consisting of Ba, Sr, Ca, Cu, Bi and W.
For the present dielectric ceramic, it is preferred that the main component of the dielectric ceramic is expressed by the Formula: xZrO.sub.2 --yTiO.sub.2 --zA.sub.(1+u)/3 B.sub.(2-u)/3 O.sub.2, wherein A denotes at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Pin, B denotes at least one component selected from the group (B) consisting of Nb and Ta, and x, y, z and u are present within the range expressed by Formula 1, wherein x, y and z denote molar fractions and u denotes a value expressed by the Formula 1.
______________________________________x + y + z = 1 Formula 10.10 .ltoreq. x .ltoreq. 0.600.20 .ltoreq. y .ltoreq. 0.600.01 .ltoreq. z .ltoreq. 0.700 .ltoreq. u .ltoreq. 1.90______________________________________
According to the dielectric ceramic, it is preferred that the accessory components of the dielectric ceramic are present within the range of 0.005 to 7.000% by weight based on the entire weight of the ceramic. The amount of the accessory component is the weight of an oxide form in which the component is present in the ceramic, and is a value which is changed into {BaO, SrO, CaO, CuO, Bi.sub.2 O.sub.3, WO.sub.3 }.
Further, it is preferred that the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta.
Preferably, the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta, and a/b (a and b denote the total of molar fractions of the components A and B) ranges from 0.5 to 1.9.
For the present dielectric ceramic, it is preferred that the main component further comprises a complex oxide formed of at least one component selected from the group (D) consisting of Sn, Hf and Ge.
Preferably, the main component of the dielectric ceramic is expressed by the Formula: xZrO.sub.2 --yTiO.sub.2 --zA.sub.(1+u)/3 B.sub.(2-u)/3 O.sub.2 --vDO.sub.2, wherein A denotes at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn, B denotes at least one component selected from the group (B) consisting of Nb and Ta, and D denotes at least one component selected from the group (D) consisting of Sn, Hf and Ge, and x, y, z, v, and u are present within the range expressed by Formula 2, wherein x, y, z and v denote molar fractions and u denotes a value expressed by the Formula 2.
______________________________________x + y + z + v = 1 Formula 20.10 .ltoreq. x .ltoreq. 0.600.20 .ltoreq. y .ltoreq. 0.600.01 .ltoreq. z .ltoreq. 0.500.001 .ltoreq. v .ltoreq. 0.200 .ltoreq. u .ltoreq. 1.90______________________________________
Further, it is preferred that the accessory components of the dielectric ceramic comprise at least one component selected from the group (C) consisting of Ba, Sr, Ca, Cu, Bi and W within the range from 0.005 to 7.000% by weight based on the entire weight of the ceramic.
For the present dielectric ceramic, it is preferred that the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of M g, Co, Zn, Ni and Mn, at least one component selected from the group (B) consisting of Nb and Ta, and at least one component selected from the group (D) consisting of Sn, Hf and Ge.
Preferably, the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn, at least one component selected from the group (B) consisting of Nb and Ta, and at least one component selected from the group (D) consisting of Sn, Hf and Ge, and a/b (a and b denote the total of molar fractions of the components A and B) ranges from 0.5 to 1.9.
The dielectric resonator of the present invention is characterized by a dielectric ceramic having the structure described above, and an electrode formed on the surface of the dielectric ceramic.
For the present dielectric resonator, it is preferred that the electrode is copper or silver.
In the structure of the present invention, the main component includes a complex oxide formed of both Zr and Ti, at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta, and as the accessory components at least one component selected from the group (C) consisting of Ba, Sr, Ca, Cu, Bi and W. Consequently, the present invention provides dielectric ceramics with less variation of temperature coefficient at a resonant frequency due to heating history during the sintering of the ZrTiO.sub.4 ceramic.
According to the preferred structure of the composition formula and the Formula 1, the present invention provides dielectric ceramics that have a high unloaded Q value and a high dielectric constant, and have a temperature coefficient at a resonant frequency which is variable as desired.
According to the dielectric ceramic expressed by the composition formula and the Formula 1, the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta. Thus, the present invention provides dielectric ceramics having a higher unloaded Q value and a high dielectric constant, and is superior in thermo-stability at a resonant frequency.
According to the dielectric ceramic expressed by the composition formula and the Formula 1, the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn and at least one component selected from the group (B) consisting of Nb and Ta, and a/b (a and b denote the total of molar fractions of the components A and B) ranges from 0.5 to 1.9. Thus, the present invention provides dielectric ceramics having a much higher unloaded Q value and a high dielectric constant, and is superior in thermo-stability at a resonant frequency.
For the present dielectric ceramics, it is preferred that the main component further comprises a complex oxide formed of at least one component selected from the group (D) consisting of Sn, Hf and Ge. Thus, the present invention provides dielectric ceramics with less variation of temperature coefficient at a resonant frequency due to heating history during the sintering of ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramics.
For the present dielectric ceramic expressed by the composition formula and the Formula 2, it is preferred that the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn, at least one component selected from the group (B) consisting of Nb and Ta, and at least one component selected from the group (D) consisting of Sn, Hf and Ge. Thus, the present invention provides dielectric ceramics having a higher unloaded Q value and a high dielectric constant, and is superior in thermo-stability at a resonant frequency.
According to the dielectric ceramic expressed by the composition formula and the Formula 2, the main component comprises a ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component selected from the group (A) consisting of Mg, Co, Zn, Ni and Mn, at least one component selected from the group (B) consisting of Nb and Ta, and at least one component selected from the group (D) consisting of Sn, Hf and Ge, and a/b (a and b denote the total of molar fractions of the components A and B) ranges from 0.5 to 1.9. Thus, the present invention provides dielectric ceramics having a much higher unloaded Q value and a high dielectric constant, and is superior in thermo-stability at a resonant frequency.
The dielectric resonator of the present invention has a high unloaded Q value and a strong electrode layer.
In the foregoing, the ZrTiO.sub.4 or crystallographical ZrTiO.sub.4 phase substituted with at least one component of each of the groups A, B and D is a phase in which both or either of Zr and Ti sites are (is) substituted with at least one of each of the groups A, B and D. Basically, the ZrTiO.sub.4 phase has an element ratio Zr/Ti=1. Actually, also in a composition area where the element ratio is slightly shifted to the direction which is higher or lower than 1 (for example, in case Zr and Ti are soluble in the ZrTiO.sub.4 phase), an area which can be regarded as the ZrTiO.sub.4 constitution is present. Such an area is crystallographically referred to as a ZrTiO.sub.4 phase.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a sectional view of a cylindrical coaxial dielectric resonator, which is axially cut off, according to an embodiment of the present invention.
FIG. 1B is a sectional view taken out along the line I--I shown in FIG. 1A.

DETAILED DESCRIPTION OF THE INVENTION
Any compound such as oxide, carbonate, hydroxide, chloride, alkoxide of the component elements described above may be used as an initial material of the dielectric ceramic according to the present invention. As blending methods of powdery raw materials, wet blending for mixing the materials with water or organic solvent in a ball mill and dry blending for mixing them by a mixer or a ball mill, etc. without using any solvent are generally known and any of these methods maybe employed. Alternatively, the alkoxide method and coprecipitation method may be used depending on the initial materials. Because the process is thus comparatively uncomplicated, and a homogeneous mixture can be easily obtained, it is desirable to employ the wet blending method for mixing them in a ball mill by using a solvent, and a dispersing agent may be additionally used for increasing the dispersing property of powders, or pH adjustment may be performed.
Although calcination of the mixture is not required, the sintering time can be reduced by calcination. Although the calcination temperature depends on the particular compositions, it is generally in the order of 1 to 8 hrs at about 700.degree. to 1200.degree. C.
As the milling method for the calcined material or mixture, any suitable method such as using a ball mill, high-speed rotor mill, media agitating mill and jet mill may be employed.
For molding, press molding is generally carried out to obtain a desired shape. Although not specifically limited, the pressure used in the press molding is generally in a range of approximately 0.5 to 2 tone/cm.sup.2. A binder used for molding may be a binder used for molding ceramics, such as a polyvinyl alcohol binder, a polyvinyl butylal binder, an acrylic resin binder or a wax binder. Although not specifically limited, the amount of the binder to be used is generally in a range of approximately 0.5 to 1% by weight by solid matter conversion.
Although sintering is not specifically limited, as it depends on the particular compositions and dimensions of the moldings, it is generally desirable to perform firing at a temperature of approximately 400.degree. to 700.degree. C. for about 1 to 24 hrs in order to remove binders, and then, at approximately 1100.degree. to 1650.degree. C. for about 2 to 100 hrs.
An example of a cylindrical coaxial dielectric resonator will be described with reference to the drawings. FIG. 1A is a sectional view of the cylindrical coaxial dielectric resonator which is axially cut off, in which electrodes 1 and 4 are continuously formed on the surface of a cylindrical dielectric ceramic 2. The electrode is not formed on the surface of an opening end 3. FIG. 1B is a sectional view taken along the line I--I shown in FIG. 1A. According to the cylindrical coaxial dielectric resonator, electromagnetic waves are incident in the direction of the opening end 3, and the resonance (TEM mode) of the electromagnetic waves in a specific frequency area is utilized to obtain the necessary output from the electrodes 1 and 4.
The present invention will be described with reference to the following examples.
EXAMPLE 1
As initial materials, ZrO.sub.2, TiO.sub.2, MgO, CoO, ZnO, NiO, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, MnCO.sub.3, BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, CuO, Bi.sub.2 O.sub.3, WO.sub.3, SnO.sub.2, HfO.sub.2 and GeO.sub.2 of high chemical purity (more than 98 wt. %) were used, weighed so as to make predetermined compositions and wet-blended with ethanol by using a ball mill. The volume ratio between the powder and ethanol was approximately 2:3.
The mixture was removed from the ball mill, dried, and calcined for 2 hrs at 1000.degree. C. in the air. The calcined product was wet-milled in the ball mill with ethanol. After the milled slurry was removed from the ball mill and dried, the powder was mixed with 8% by weight of polyvinyl alcohol solution of 6 vol. % in concentration as a binder, homogenized, and granulated by sieving through a 32 mesh screen. The granulated powder was molded into a disk of 7 mm in diameter and approximately 3 mm in thickness by using molds and an oil hydraulic press at a molding pressure of 1.3 ton/cm.sup.2.
The molding was placed in a magnesia vessel of high purity, kept in the air at a temperature of 600.degree. C. for 4 hrs to remove binders, then retained in the air at 1200.degree. to 1500.degree. C. for 24 hrs for sintering, and quenched (taken out of a furnace and air-cooled) or slowly cooled down to 1000.degree. C. (at a cooling rate of 20.degree. C./hr) thereafter, and dielectric ceramics were obtained.
The resonant frequency was obtained from measurement by the dielectric rod resonator method. The temperature coefficient at a resonant frequency .tau..sub.f was obtained in a range between -25.degree. C. and 85.degree. C.
The compositions of main components and the amount of accessory components, which are to be added, of the dielectric ceramics thus produced are shown in Tables 1 and 2, respectively. Cooling conditions after sintering and a temperature coefficient at a resonant frequency (ppm/.degree. C.) are shown in Table 3. In Tables 1 to 3, comparative examples have an asterisk.
TABLE 1__________________________________________________________________________Sample Composition (molar fraction)No. Zr Ti Mg Co Zn Ni Mn Nb Ta Sn Hf Ge__________________________________________________________________________*1,*2 0.50 0.50 0 0 0 0 0 0 0 0 0 03,4 0.35 0.50 0.05 0 0 0 0 0.10 0 0 0 05,6 0.35 0.50 0 0.05 0 0 0 0.10 0 0 0 07,8 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.10 0 0 0 0 9,10 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.10 0 0 0 011,12 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.10 0 0 0 013,14 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0 0 0*15*16 0.40 0.50 0 0 0 0 0 0 0 0.10 0 0*17*18 0.32 0.50 0 0.03 0 0 0 0.05 0 0.10 0 019,20 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0.010 0 021,22 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0 0.01 023,24 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0 0 0.0125,26 0.35 0.50 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0.01 0.01 0.01__________________________________________________________________________
TABLE 2______________________________________Sample Amount of additive (wt. %)No. Ba Sr Ca Cu Bi W______________________________________*1,*2 0 0.1 0 0 0 03,4 0 0.1 0 0 0 05,6 0.1 0 0 0 0 07,8 0 0 0 0 0.1 0 9,10 0 0 0 0.1 0 011,12 0 0 0 0 0 0.113,14 0.1 0.1 0.1 0.1 0 0*15*16 0 0 0 0 0 0*17*18 0 0 0 0 0 019,20 0.1 0.1 0.1 0.1 0 021,22 0.1 0 0 0 0 023,24 0 0.1 0 0 0 025,26 0.1 0.1 0.1 0.1 0 0______________________________________
TABLE 3______________________________________Sample No. Cooling condition after sintering .tau..sub.f (ppm/.degree.C.)______________________________________*1 Quenching 58.9*2 Slow cooling 69.13 Quenching 8.24 Slow cooling 8.95 Quenching 5.56 Slow cooling 4.87 Quenching 9.48 Slow cooling 9.39 Quenching 9.710 Slow cooling 10.111 Quenching 9.812 Slow cooling 9.613 Quenching 9.814 Slow cooling 9.7*15 Quenching -5.7*16 Slow cooling 1.2*17 Quenching -22.5*18 Slow cooling -16.319 Quenching 5.820 Slow cooling 4.221 Quenching 0.922 Slow cooling 1.223 Quenching 9.524 Slow cooling 9.925 Quenching 8.526 Slow cooling 9.7______________________________________
As recognized from the results shown in Table 3, in dielectric ceramics of sample Nos. 3 to 14 and 19 to 26 of the present example, the variation of temperature coefficient at a resonant frequency due to the heating history during sintering of ZrTiO.sub.4 and ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramics is reduced.
EXAMPLE 2
As initial materials, ZrO.sub.2, TiO.sub.2, MgO, CoO, ZnO, NiO, MnCO.sub.3, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, CuO, Bi.sub.2 O.sub.3, and WO.sub.3 of high chemical purity which are the same as in Example 1 were used, weighed so as to make a predetermined compositions and wet-blended with ethanol by using a ball mill. The volume ratio between the powder and ethanol was approximately 2:3.
The mixture was removed from the ball mill, dried, and calcined for 2 to 8 hrs at 800.degree. to 1250.degree. C. in the air. The calcined product was wet-milled in the ball mill with ethanol. After the milled slurry was removed from the ball mill and dried, the powder was mixed with 8% by weight of polyvinyl alcohol solution of 6 vol. % in concentration added thereto as a binder, homogenized, and granulated by sieving through 32 mesh screen. The granulated powder was molded into a disk of 7 mm in diameter and approximately 3 mm in thickness by using molds and an oil hydraulic press at a molding pressure of 1.3 ton/cm.sup.2.
The molding was placed in a magnesia vessel of high purity, kept in the air at a temperature of 400.degree. to 700.degree. C. for 4 to 8 hrs to remove binders, retained in the air at 1200.degree. C. to 1650.degree. C. for 1 to 100 hrs for sintering, and dielectric ceramics were obtained.
The resonant frequency. unloaded Q (Qu) value and dielectric constant .di-elect cons..sub.r were obtained from measurement by the dielectric rod resonator method. The temperature coefficient at a resonant frequency .tau..sub.f was obtained in a range between -25.degree. C. and 85.degree. C. The resonant frequency was obtained in a range between 4 GHz and 12 GHz.
The compositions of main components and the amount of accessory components, which are to be added, of the dielectric ceramics thus produced are shown in Table 4. The dielectric constant thus obtained, the temperature at a resonant frequency .tau..sub.f (ppm/.degree. C.) and the unloaded Q value are shown in Table 5. In Tables 4 and 5, comparative examples have an asterisk.
TABLE 4______________________________________ CompositionSam- of main component Accessoryple (molar fraction) (value) componentNo. A B x y z u (wt. %)______________________________________*27 Mg Nb 0.400 0.150 0.450 0 Sr 0.005*28 Co Nb 0.400 0.150 0.450 0 Sr 0.005*29 Zn Nb 0.400 0.150 0.450 0 Ba 0.005*30 Ni Nb 0.400 0.150 0.450 0 Ca 0.00531 Mg Nb 0.200 0.200 0.600 0 Sr 1.00032 Co Nb 0.200 0.200 0.600 0 Sr 1.00033 Ni Nb 0.200 0.200 0.600 0 Sr 1.00034 Mg Nb 0.450 0.200 0.350 0 Sr 0.50035 Co Nb 0.450 0.200 0.350 0 Sr 0.50036 Mg Nb 0.200 0.600 0.200 0 Ba 0.50037 Zn Nb 0.200 0.600 0.200 0 Ba 0.500*38 Mg Nb 0.150 0.700 0.150 0 Sr 1.000*39 Mg Nb 0.150 0.120 0.730 0 Ba 0.50040 Mg Nb 0.100 0.200 0.700 0 Ba 0.50041 Ni Nb 0.100 0.200 0.700 0 Ba 0.500*42 -- -- 0.550 0.450 0 0 -- 043 Mg Nb 0.490 0.500 0.010 0 Ba 0.00544 Co Nb 0.490 0.500 0.010 0 Ba 0.00545 Zn Nb 0.490 0.500 0.010 0 Ba 0.00546 Ni Nb 0.490 0.500 0.010 0 Ba 0.00547 Mg Nb 0.300 0.300 0.400 0 Sr 1.00048 Mg Nb 0.400 0.400 0.200 0 Sr 0.00549 Co Nb 0.400 0.400 0.200 0 Sr 0.00550 Zn Nb 0.400 0.400 0.200 0 Sr 0.00551 Mg Nb 0.340 0.520 0.140 0 Sr 0.10052 Co Nb 0.340 0.520 0.140 0 Sr 0.10053 Zn Nb 0.340 0.520 0.140 0 Sr 0.10054 Ni Nb 0.340 0.520 0.140 0 Sr 0.10055 Mg Nb 0.450 0.450 0.100 0 Sr 0.100*56 Mg Nb 0.650 0.200 0.100 0 Ca 0.100*57 Co Nb 0.650 0.200 0.100 0 Ca 0.10058 Mg Nb 0.600 0.300 0.100 0 Ca 0.10059 Mg Nb 0.100 0.400 0.500 0 Bi 0.10060 Ni Nb 0.100 0.400 0.500 0 Bi 0.100*61 Mg Nb 0.050 0.500 0.450 0 Ca 0.100*62 Co Nb 0.050 0.500 0.450 0 Bi 0.10063 Mg Nb 0.450 0.350 0.200 0 Sr 1.00064 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 Cu 0.00565 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 Cu 0.10066 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 0.00567 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 0.10068 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 1.00069 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 2.00070 Mg Nb 0.350 0.450 0.200 0 Sr 1.00071 Mg Nb 0.350 0.450 0.200 0.01 Sr 1.00072 Co Nb 0.350 0.450 0.200 0.01 Sr 1.00073 Zn Nb 0.350 0.450 0.200 0.01 Sr 1.00074 Ni Nb 0.350 0.450 0.200 0.01 Sr 1.00075 Mg Nb 0.350 0.450 0.200 0.05 Sr 1.00076 Mg Nb 0.350 0.450 0.200 0.20 Sr 1.00077 Co Nb 0.350 0.450 0.200 0.20 Sr 1.00078 Mg Nb 0.350 0.450 0.200 0.50 Sr 1.00079 Mg Nb 0.350 0.450 0.200 1.00 Sr 1.00080 Mg Nb 0.350 0.450 0.200 1.90 Sr 1.00081 Co Nb 0.350 0.450 0.200 1.90 Sr 1.00082 Mg Nb 0.350 0.450 0.200 2.00 Sr 1.00083 Mg.sub.1/4 Co.sub.1/4 Nb 0.340 0.520 0.140 0 Sr 0.100 Zn.sub.1/4 Ni.sub.1/484 Mg.sub.1/2 Co.sub.1/2 Nb 0.340 0.520 0.140 1.00 Sr 0.10085 Mg.sub.1/3 Co.sub.1/3 Ta 0.340 0.520 0.140 1.00 Sr 0.100 Ni.sub.1/386 Mg.sub.1/4 Co.sub.1/4 Nb.sub.1/2 0.340 0.520 0.140 1.00 Sr 0.100 Zn.sub.1/4 Ni.sub.1/4 Ta.sub.1/287 Mg.sub.39/40 Nb.sub.1/2 0.340 0.520 0.140 0.02 Bi 0.100 Mn.sub.1/40 Ta.sub.1/288 Mg.sub.113/200 Nb 0.328 0.502 0.170 0.41 Bi 0.100 Mn.sub.87/20089 Mn Nb 0.200 0.600 0.200 0 Ca 0.10090 Mg Nb 0.300 0.400 0.300 1.00 Sr 0.50091 Mg Nb 0.300 0.400 0.300 1.00 Ba 0.50092 Mg Nb 0.300 0.400 0.300 1.00 Ca 0.50093 Mg Nb 0.300 0.400 0.300 1.00 Bi 0.50094 Mg Nb 0.300 0.400 0.300 1.00 Ba 0.500 Sr 0.500 Ca 0.500 Bi 0.50095 Mg Nb 0.300 0.400 0.300 1.00 Sr 1.50096 Mg Nb 0.300 0.400 0.300 1.00 Sr 3.00097 Mg Nb 0.300 0.400 0.300 1.00 Sr 7.000*98 Mg Nb 0.300 0.400 0.300 1.00 Sr 8.000______________________________________
TABLE 5______________________________________Sample No. .epsilon..sub.r .tau..sub.f Qu______________________________________*27 30.1 -84.9 950*28 29.9 -70.5 850*29 30.0 -88.7 970*30 30.8 -69.4 83031 32.5 -10.8 800032 31.3 -8.9 900033 30.9 -7.8 810034 32.3 -32.1 430035 33.1 -19.5 480036 57.5 47.4 530037 55.5 40.2 6100*38 75.8 225.2 370*39 28.0 -84.8 98040 33.8 -8.5 960041 26.8 -5.4 9600*42 45.8 250.8 180043 44.5 42.3 390044 44.3 42.0 360045 43.8 45.9 310046 44.5 46.8 310047 39.3 15.3 600048 42.0 0.3 970049 43.1 12.1 850050 42.2 -5.3 830051 43.1 9.3 790052 45.1 13.4 510053 44.1 1.3 790054 42.9 16.2 510055 41.5 10.3 5500*56 35.7 60.5 870*57 29.5 21.3 62058 40.2 45.9 400059 65.5 48.9 330060 55.8 48.1 4100*61 82.9 151.8 830*62 86.8 213.3 42063 42.8 14.3 480064 45.6 20.0 470065 43.7 28.7 400066 45.7 19.5 490067 42.9 16.3 460068 40.2 7.3 420069 37.1 4.2 400070 45.8 19.7 470071 44.5 14.1 490072 47.0 35.4 470073 43.7 19.8 510074 44.2 40.2 470075 42.7 14.0 510076 43.8 10.5 670077 45.2 30.4 710078 42.9 9.3 720079 41.5 8.5 750080 35.2 0.1 600081 32.3 -9.8 520082 34.2 -5.3 430083 45.1 17.3 570084 43.8 6.7 750085 40.1 9.8 850086 41.8 4.9 730087 43.4 9.8 720088 42.9 8.7 680089 61.2 48.5 350090 41.2 -25.8 850091 40.3 -35.7 920092 40.7 -36.4 630093 44.3 -24.1 580094 42.5 -34.2 490095 42.8 -17.5 810096 44.5 -3.2 700097 52.1 38.5 3800*98 59.3 58.3 910______________________________________
As is apparent from the results shown in Table 5, in dielectric ceramic compositions within a composition range of the invention, the dielectric constant is kept at a high value at microwave frequencies, while a high unloaded Q value is provided.
On the contrary, when X is higher than 0.60, the unloaded Q value is significantly reduced as observed in sample Nos. 56 and 57. The objects of the invention cannot readily be achieved. When x is lower than 0.10, the unloaded Q value is reduced as observed in Example Nos. 61 and 62.
When y is higher than 0.60, the unloaded Q value is significantly reduced as observed in sample No. 38. Further, when y is lower than 0.20, the unloaded Q value is significantly reduced as observed in sample Nos. 27 to 30 and No. 39. Consequently, the objects of the invention cannot readily be achieved.
When z is higher than 0.70, the unloaded Q value is reduced as observed in sample No. 39. Further, when z is lower than 0.01, the unloaded Q value is reduced as observed in sample No. 42. Consequently, the objects of the invention cannot readily be achieved.
Additionally, the unloaded Q value can be improved by increasing u to a higher value than 0. However, when u exceeds 1.90, the unloaded Q value is reduced as observed in sample No. 82. Also in the case of sample No. 82, the properties were better than those of conventional dielectric ceramics.
When the amount of accessory component to be added is higher than 7.000% by weight, the unloaded Q value is significantly reduced as observed in sample No. 98. Consequently, the objects of the invention cannot readily be achieved.
It was confirmed within the composition range of the example that the unloaded Q value was improved by using A, which is at least one element selected from Mg, Co, Zn, Ni, and Mn and B, which is at least one element selected from Nb and Ta, oxides were calcined in advance at a temperature of 800.degree. to 1200.degree. C.
Additionally, a ZrTiO.sub.4 phase or one recognized as being a crystallographical ZrTiO.sub.4 phase was confirmed by powder X-ray diffraction of a dielectric ceramic within the composition range of Examples 1 and 2 of the invention. It was further confirmed in composition analysis by a local X-ray diffractometer of a fracture surface and polished surface of the dielectric ceramic having, as the main component, ZrTiO.sub.4 phase or crystallographical ZrTiO.sub.4 phase that all components of Zr, Ti, A and B (wherein A is at least one component selected from Mg, Co, Zn, Ni and Mn, and B is at least one component selected from Nb and Ta) were present in a single grain, and their composition ratio was consistent with the composition ratio between other grains that constitute the main phase in the same dielectric ceramic. It was also confirmed that all components A and B blended were present in a single grain. Moreover, it was confirmed that a dielectric ceramic with components Zr, Ti, A and B present in a grain which constitutes the main phase showed a higher lattice constant in comparison with ZrTiO.sub.4 ceramic obtained under the same sintering conditions. Accordingly, it was confirmed that components A and B are substituted in the ZrTiO.sub.4 phase or the crystallographical ZrTiO.sub.4 phase.
Such dielectric ceramics specifically showed a high unloaded Q value and a high dielectric constant, and were superior in thermo-stability at a resonant frequency. The unloaded Q value was even higher when the molar ratio a/b of the component A to the component B was 0.5 or more and 1.9 or less.
As is apparent from the results described above, it was confirmed that the dielectric ceramics of the example are capable of maintaining the dielectric constant at a high value at microwave frequencies, while providing a high unloaded Q value, and are superior in thermo-stability at a resonant frequency.
EXAMPLE 3
As initial materials, ZrO.sub.2, TiO.sub.2, MgO, CoO, ZnO, NiO, MnCO.sub.3, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, SnO.sub.2, HfO.sub.2, GeO.sub.2, BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, CuO, Bi.sub.2 O.sub.3, and WO.sub.3 of high chemical purity which are the same as in Example 1 were used, weighed so as to make predetermined compositions and wet-blended with ethanol by using a ball mill. The volume ratio between the powder and ethanol was approximately 2:3.
The mixture was removed from the ball mill, dried, and calcined for 2 to 8 hrs at 800.degree. C. to 1250.degree. C. in the air. The calcined product was wet-milled in the ball mill with ethanol. After the milled slurry was removed from the ball mill and dried, the powder was mixed with 8% by weight of polyvinyl alcohol solution of 6 vol. % in concentration added thereto as a binder, homogenized, and granulated by sieving through a 32 mesh screen. The granulated powder was molded into a disk of 7 mm in diameter and approximately 3 mm in thickness by using molds and an oil hydraulic press at a molding pressure of 1.3 ton/cm.sup.2.
The molding was placed in a magnesia vessel of high purity, kept in the air at a temperature of 400.degree. C. to 700.degree. C. for 4 to 8 hrs to remove binders, retained in the air at 1200.degree. C. to 1650.degree. C. for 1 to 100 hrs for sintering, and dielectric ceramics were obtained.
The resonant frequency, unloaded Q (Qu) value and dielectric constant .di-elect cons..sub.r were obtained from measurement by the dielectric rod resonator method. The temperature coefficient at a resonant frequency .tau..sub.f was obtained in a range between -25.degree. C. and 85.degree. C. The resonant frequency was obtained in a range between 4 GHz and 12 GHz.
The compositions of main components and the amount of accessory components, which are to be added, of the dielectric ceramics thus produced are shown in Table 6. The dielectric constant thus obtained, the temperature at a resonant frequency .tau..sub.f (ppm/.degree. C.) and the unloaded Q value are shown in Table 7. In Tables 6 and 7, comparative examples have an asterisk.
TABLE 6__________________________________________________________________________ Composition of main component AccessorySample (molar fraction) (value) componentNo. A B D x y z v u (wt. %)__________________________________________________________________________*99 Mg Nb Sn 0.400 0.150 0.400 0.050 0 Sr 0.005100 Mg Nb Sn 0.200 0.200 0.400 0.200 0 Sr 1.000101 Co Nb Sn 0.200 0.200 0.400 0.200 0 Sr 1.000102 Ni Nb Sn 0.200 0.200 0.400 0.200 0 Sr 1.000103 Mg Nb Sn 0.450 0.200 0.300 0.050 0 Sr 0.500104 Co Nb Sn 0.450 0.200 0.300 0.050 0 Sr 0.500105 Mg Nb Sn 0.200 0.600 0.100 0.100 0 Ba 0.500106 Zn Nb Sn 0.200 0.600 0.150 0.050 0 Ba 0.500*107 Mg Nb Sn 0.150 0.700 0.100 0.050 0 Sr 1.000*108 Mg Nb Sn 0.150 0.120 0.530 0.200 0 Ba 0.500109 Mg Nb Sn 0.100 0.200 0.500 0.200 0 Ba 0.500*110 Mg Nb Sn 0.100 0.200 0.300 0.400 0 Ba 0.500*111 -- -- -- 0.550 0.450 0 0 0 -- 0112 Mg Nb Sn 0.490 0.450 0.010 0.050 0 Ba 0.005113 Mg Nb Sn 0.300 0.300 0.300 0.100 0 Sr 1.000114 Mg Nb Sn 0.400 0.400 0.199 0.001 0 Sr 0.005115 Co Nb Sn 0.400 0.400 0.199 0.001 0 Sr 0.005116 Zn Nb Sn 0.400 0.400 0.199 0.001 0 Sr 0.005117 Mg Nb Sn 0.450 0.450 0.050 0.050 0 Sr 0.100*118 Mg Nb Sn 0.650 0.200 0.050 0.050 0 Ca 0.100119 Mg Nb Sn 0.600 0.300 0.050 0.050 0 Ca 0.100*120 Mg Nb Sn 0.050 0.500 0.400 0.050 0 Ca 0.100121 Mg Nb Sn 0.450 0.350 0.150 0.050 0 Sr 1.000122 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 Cu 0.005123 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 Cu 0.100124 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 W 0.005125 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 W 0.100126 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 W 1.000127 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000 W 2.000128 Mg Nb Sn 0.350 0.450 0.150 0.050 0 Sr 1.000129 Mg Nb Sn 0.350 0.450 0.150 0.050 0.01 Sr 1.000130 Mg Nb Sn 0.350 0.450 0.150 0.050 0.05 Sr 1.000131 Mg Nb Sn 0.350 0.450 0.150 0.050 0.20 Sr 1.000132 Mg Nb Sn 0.350 0.450 0.150 0.050 0.50 Sr 1.000133 Mg Nb Sn 0.350 0.450 0.150 0.050 1.00 Sr 1.000134 Mg Nb Sn 0.350 0.450 0.150 0.050 1.90 Sr 1.000135 Co Nb Sn 0.350 0.450 0.150 0.050 1.90 Sr 1.000136 Mg Nb Sn 0.350 0.450 0.150 0.050 2.00 Sr 1.000137 Mg.sub.1/4 Nb Sn 0.340 0.520 0.130 0.010 0 Sr 0.100 Co.sub.1/4 Zn.sub.1/4 Ni.sub.1/4138 Mg.sub.1/3 Ta Sn 0.340 0.520 0.130 0.010 1.00 Sr 0.100 Co.sub.1/3 Ni.sub.1/3139 Mg.sub.1/4 Nb.sub.1/2 Sn 0.340 0.520 0.130 0.010 1.00 Sr 0.100 Co.sub.1/4 Ta.sub.1/2 Zn.sub.1/4 Ni.sub.1/4140 Mn Nb Sn 0.200 0.600 0.190 0.010 0 Ca 0.100141 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 0.500142 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ba 0.500143 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ca 0.500144 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Bi 0.500145 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ba 0.500 Sr 0.500 Ca 0.500 Bi 0.500146 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.500147 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 3.000148 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 7.000*149 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 8.000150 Mg Nb Hf 0.350 0.450 0.150 0.050 1.90 Sr 1.000151 Mg Nb Ge 0.350 0.450 0.150 0.050 1.90 Sr 1.000__________________________________________________________________________
TABLE 7______________________________________Sample No. .epsilon..sub.r .tau..sub.f Qu______________________________________*99 29.8 -85.3 1200100 27.6 -20.4 9600101 26.7 -17.5 7500102 28.3 -15.4 6900103 31.7 -34.0 4000104 32.9 -22.5 4100105 55.4 28.3 5500106 53.1 15.3 5800*107 74.3 225.0 480*108 21.3 -91.2 1200109 30.2 -14.5 8600*110 24.3 -60.5 400*111 45.8 250.8 1800112 42.5 23.2 4800113 37.2 7.8 6500114 41.5 -0.2 8300115 43.0 11.5 7800116 42.0 -5.8 6800117 40.1 4.2 5100*118 33.0 60.0 320119 40.1 42.3 3100*120 82.3 147.2 200121 42.1 10.3 4100122 43.1 15.5 4000123 41.0 25.7 3800124 43.1 15.1 4200125 40.9 11.9 4000126 38.0 3.1 3700127 35.4 -1.0 3500128 43.2 15.3 4000129 42.9 14.9 4500130 41.2 3.2 5000131 40.5 0.2 6100132 37.2 -4.5 6300133 34.3 -15.5 7000134 30.1 -32.5 7100135 30.9 -35.4 5800136 28.9 -37.4 3900137 44.7 15.3 5100138 39.7 9.3 8100139 40.9 4.5 6500140 60.3 44.9 3800141 37.9 -30.3 7800142 36.1 -35.4 8100143 36.9 -35.1 5400144 42.3 -25.9 3800145 40.1 -33.2 3500146 39.3 -20.1 6900147 44.5 1.2 5800148 50.2 39.5 4100*149 61.5 65.4 320150 45.3 -28.5 5300151 30.9 -34.5 4900______________________________________
As is apparent from the results shown in Table 7, it was confirmed that, in dielectric ceramic compositions within a composition range of the present invention, the dielectric constant is kept at a high value at microwave frequencies, while a high unloaded Q value is provided.
On the contrary, when X is higher than 0.60, the unloaded Q value is significantly reduced as observed in sample No. 118. Consequently, the objects of the invention cannot readily be achieved. When x is lower than 0.10, the unloaded Q value is reduced as observed in sample No. 120. Consequently, the objects of the invention cannot readily be achieved.
When y is higher than 0.60, the unloaded Q value is significantly reduced as observed in sample No. 107. Further, when y is lower than 0.20, the unloaded Q value is significantly reduced as observed in sample Nos. 99 and 108. Consequently, the objects of the invention cannot readily be achieved.
When z is higher than 0.50, the unloaded Q value is reduced as observed in sample No. 108. When z is lower than 0.01, the unloaded Q value is reduced as observed in sample No. 111. Consequently, the objects of the invention cannot readily be achieved.
Additionally, the unloaded Q value can be improved by increasing w to a higher value than 0. However, when w exceeds 1.90, the unloaded Q value is reduced as shown in sample No. 136. Also in the case of sample No. 136, the properties were better than those of conventional dielectric ceramics.
When the amount of accessory component to be added is higher than 7.000% by weight, the unloaded Q value is significantly reduced as observed in sample No. 149. Consequently, the objects of the invention cannot readily be achieved.
It was confirmed within the composition range of the example that the unloaded Q value was improved by using A, which is at least one element selected from Mg, Co, Zn, Ni, and Mn and B, which is at least one element selected from Nb and Ta, oxides that were calcined in advance at a temperature of 800.degree. C. to 1200.degree. C.
Additionally, a ZrTiO.sub.4 phase or one recognized as being a crystallographical ZrTiO.sub.4 phase was confirmed by powder X-ray diffraction of a dielectric ceramic within the composition range of Examples 1 and 3 of the invention. It was further confirmed in composition analysis by a local X-ray diffractometer of a fracture surface and polished surface of the dielectric ceramic having as the main component ZrTiO.sub.4 phase or crystallographical ZrTiO.sub.4 phase, that all components of Zr, Ti, A, B and D (wherein A is at least one component selected from Mg, Co, Zn, Ni and Mn, B is at least one component selected from Nb and Ta, and D is at least one component selected from Sn, Hf and Ge) were present in a single grain, and their composition ratio was consistent with the composition ratio between other grains that constitute the main phase in the same dielectric ceramic. It was also confirmed that all components A, B and D blended were present in a single grain.
Moreover, it was confirmed that a dielectric ceramic with components Zr, Ti, A, B and D present in a grain which constitutes the main phase showed a higher lattice constant in comparison with ZrTiO.sub.4 ceramic obtained under the same sintering conditions. Accordingly, it was confirmed that components A, B and D are substituted in the ZrTiO.sub.4 phase or the crystallographical ZrTiO.sub.4 phase.
Such dielectric ceramics specifically showed a high unloaded Q value and a high dielectric constant, and were superior in thermo-stability at a resonant frequency. The unloaded Q value was even higher when the molar ratio a/b of the component A to the component B was 0.5 or more and 1.9 or less
As is obvious from the results described above, it was confirmed that the dielectric ceramics of the example are capable of maintaining the dielectric constant at a high value at microwave frequencies, while providing a high unloaded Q value, and are superior in thermo-stability at a resonant frequency.
EXAMPLE 4
As initial materials, ZrO.sub.2, TiO.sub.2, MgO, CoO, ZnO, NiO, MnCO.sub.3, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, CuO, Bi.sub.2 O.sub.3, and WO.sub.3 of high chemical purity were used, weighed so as to make predetermined compositions and wet-blended with ethanol by using a ball mill. The volume ratio between the powder and ethanol was approximately 2:3.
The mixture was removed from the ball mill, dried, and calcined for 2 to 8 hrs at 800.degree. C. to 1250.degree. C. in the air. The calcined product was wet-milled in the ball mill with ethanol. After the milled slurry was removed from the ball mill and dried, the powder was mixed with 8% by weight of polyvinyl alcohol solution of 6 vol. % in concentration added thereto as a binder, homogenized, and granulated by sieving through 32 mesh screen. The granulated powder was molded into a cylindrical coaxial shape by using molds and an oil hydraulic press at a molding pressure of 1.3 ton/cm.sup.2.
The molding was placed in a magnesia vessel of high purity, kept in the air at a temperature of 400.degree. C. to 700.degree. C. for 4 to 8 hrs to remove binders, retained in the air at 1200.degree. C. to 1650.degree. C. for 1 to 100 hrs for sintering, and cylindrical coaxial dielectric ceramics having an outer diameter of 7.2 mm and an inner diameter of 3.6 mm were obtained.
When copper was used for an electrode material, a copper coat having a thickness of about 3.5 .mu.m was formed on the dielectric ceramic surface by the electroless plating method. When silver was used for the electrode material, silver paste which is on the market was burned to form a silver coat. In both cases, one of two end faces of the coaxial type device ground the electrode material, so that a TEM mode resonator was obtained.
The compositions of main components and the amount of accessory components, which are to be added, of the dielectric resonator thus produced are shown in Table 8, the electrode material which was used, the unloaded Q value and the bond strength are shown in Table 9. The resonant frequency was 1.3 to 1.7 GHz. In Tables 8 and 9, comparative examples have an asterisk.
TABLE 8______________________________________ Composition ofSam- main component Accessoryple (molar fraction) (value) componentNo. A B x y z u (wt. %)______________________________________*152 Mg Nb 0.340 0.520 0.140 0 -- 0*153 -- -- 0.550 0.450 0 0 -- 0154 Mg Nb 0.340 0.520 0.140 0 Sr 0.100155 Co Nb 0.340 0.520 0.140 0 Sr 0.100156 Zn Nb 0.340 0.520 0.140 0 Sr 0.100157 Ni Nb 0.340 0.520 0.140 0 Sr 0.100158 Mg Nb 0.100 0.400 0.500 0 Bi 0.100159 Ni Nb 0.100 0.400 0.500 0 Bi 0.100160 Mg Nb 0.450 0.350 0.200 0 Sr 1.000161 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 Cu 0.005162 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 Cu 0.100163 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 0.005164 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 0.100165 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 1.000166 Mg Nb 0.350 0.450 0.200 0 Sr 1.000 W 2.000167 Mg Nb 0.350 0.450 0.200 0 Sr 1.000168 Mg Nb 0.350 0.450 0.200 0.05 Sr 1.000169 Mg Nb 0.350 0.450 0.200 0.20 Sr 1.000170 Co Nb 0.350 0.450 0.200 0.20 Sr 1.000171 Mg Nb 0.350 0.450 0.200 0.50 Sr 1.000172 Mg Nb 0.350 0.450 0.200 1.00 Sr 1.000173 Mg Nb 0.350 0.450 0.200 1.90 Sr 1.000174 Co Nb 0.350 0.450 0.200 1.90 Sr 1.000175 Mg.sub.1/3 Co.sub.1/3 Ta 0.340 0.520 0.140 1.00 Sr 0.100 Ni.sub.1/3176 Mg.sub.1/4 Co.sub.1/4 Nb.sub.1/2 0.340 0.520 0.140 1.00 Sr 0.100 Zn.sub.1/4 Ni.sub.1/4 Ta.sub.1/2177 Mg.sub.39/40 Nb.sub.1/2 0.340 0.520 0.140 0.02 Bi 0.100 Mn.sub.1/40 Ta.sub.1/2178 Mg.sub.113/200 Nb 0.328 0.502 0.170 0.41 Bi 0.100 Mn.sub.87/200179 Mg Nb 0.300 0.400 0.300 1.00 Ba 0.500180 Mg Nb 0.300 0.400 0.300 1.00 Ca 0.500181 Mg Nb 0.300 0.400 0.300 1.00 Bi 0.500182 Mg Nb 0.300 0.400 0.300 1.00 Ba 0.500 Sr 0.500 Ca 0.500 Bi 0.500183 Mg Nb 0.300 0.400 0.300 1.00 Sr 1.500184 Mg Nb 0.300 0.400 0.300 1.00 Sr 1.500185 Mg Nb 0.300 0.400 0.300 1.00 Sr 3.000186 Mg Nb 0.300 0.400 0.300 1.00 Sr 7.000*187 Mg Nb 0.300 0.400 0.300 1.00 Sr 8.000______________________________________
TABLE 9______________________________________Sample Electrode Bond strengthNo. material Qu (kg/4 mm.sup.2)______________________________________*152 Cu 150 0.4*153 Cu Unmeasurable due to electrode peeling154 Cu 550 6.8155 Cu 520 6.4156 Cu 500 6.3157 Cu 510 6.0158 Cu 530 6.1159 Cu 500 6.3160 Cu 630 9.7161 Cu 670 12.0162 Cu 650 12.0163 Cu 660 11.5164 Cu 650 10.9165 Cu 620 10.7166 Cu 600 11.0167 Cu 650 9.3168 Cu 670 9.1169 Cu 690 9.5170 Cu 670 9.1171 Cu 710 8.8172 Cu 740 9.6173 Cu 750 9.0174 Cu 740 8.9175 Cu 580 7.3176 Cu 620 9.1177 Cu 640 7.8178 Cu 630 7.5179 Cu 640 9.7180 Cu 530 6.1181 Cu 610 9.3182 Cu 670 11.5183 Cu 750 10.4184 Ag 730 12.0185 Cu 740 11.5186 Cu 680 12.0*187 Cu 210 10.5______________________________________
As is apparent from the results shown in Table 9, the dielectric resonators of the embodiment had a high bond strength also when an electroless copper electrode is used in the same way as a silver electrode. For this reason, the unloaded Q value is high in a microwave frequency band and the resonant frequency can be prevented from deviating due to electrode peeling so that electric characteristics are stable. In addition, the dielectric resonators of the invention are suitable for forming electrodes by copper plating, so that they are suitable for large scale production and manufacturing costs can be reduced.
Additionally, a ZrTiO.sub.4 phase or one recognized as being a crystallographical ZrTiO.sub.4 phase was confirmed by powder X-ray diffraction of a dielectric ceramic within the composition range of Example 4 of the invention. It was further confirmed in composition analysis by a local X-ray diffractometer of a fracture surface and polished surface of the dielectric ceramic having as the main component ZrTiO.sub.4 phase or crystallographical ZrTiO.sub.4 phase, that all components of Zr, Ti, A and B (wherein A is at least one component selected from Mg, Co, Zn, Ni and Mn, and B is at least one component selected from Nb and Ta) were present in a single grain, and their composition ratio was consistent with the composition ratio between other grains that constitute the main phase in the same dielectric ceramic. It was also confirmed that all components A and B blended were present in a single grain. Moreover, it was confirmed that a dielectric ceramic with components Zr, Ti, A and B present in a grain which constitutes the main phase showed a higher lattice constant in comparison with ZrTiO.sub.4 ceramic obtained under the same sintering conditions. Accordingly, it was confirmed that components A and B are substituted in the ZrTiO.sub.4 phase or the crystallographical ZrTiO.sub.4 phase.
Such dielectric ceramics specifically showed a high unloaded Q value and a high dielectric constant, and were superior in thermo-stability at a resonant frequency. The unloaded Q value was even higher when the molar ratio a/b of the component A to the component B was 0.5 or more and 1.9 or less. The dielectric resonators having such dielectric ceramics had an unloaded Q value which is specially high, and a high electrode bond strength.
As is obvious from the results described above, it was confirmed that the dielectric resonators of the example have the unloaded Q value which is specially high at a microwave frequency band. Moreover, the resonant frequency can be prevented from deviating due to electrode peeling. In addition, the dielectric resonators of the invention are suitable for forming electrodes by copper plating, so that they can be produced on a large scale and manufacturing costs can be reduced.
EXAMPLE 5
As initial materials, ZrO.sub.2, TiO.sub.2, MgO, CoO, ZnO, NiO, MnCO.sub.3, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, SnO.sub.2, HfO.sub.2, GeO.sub.2, BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, CuO, Bi.sub.2 O.sub.3, and WO.sub.3 of high chemical purity which are the same as in Example 1 were used, weighed so as to make predetermined compositions and wet-blended with ethanol by using a ball mill. The volume ratio between the powder and ethanol was approximately 2:3.
The mixture was removed from the ball mill, dried, and calcined for 2 to 8 hrs at 800.degree. C. to 1250.degree. C. in the air. The calcined product was wet-milled in the ball mill with ethanol. After the milled slurry was removed from the ball mill and dried, the powder was mixed with 8% by weight of polyvinyl alcohol solution of 6 vol. % in concentration added thereto as a binder, homogenized, and granulated by sieving through 32 mesh screen. The granulated powder was molded into a cylindrical coaxial shape by using molds and an oil hydraulic press at a molding pressure of 1.3 ton/cm.sup.2.
The molding was placed in a magnesia vessel of high purity, kept in the air at a temperature of 400.degree. C. to 700.degree. C. for 4 to 8 hrs to remove binders, retained in the air at 1200.degree. C. to 1650.degree. C. for 1 to 100 hrs for sintering, and cylindrical coaxial dielectric ceramics having an outer diameter of 7.2 mm and an inner diameter of 3.6 mm were obtained.
When copper was used for an electrode material, a copper coat having a thickness of about 3.5 .mu.m was formed on the dielectric ceramic surface by the electroless plating method. When silver was used for the electrode material, silver paste which is on the market was burned to form a silver coat. In both cases, one of two end faces of the coaxial type device ground the electrode material, so that a TEM mode resonator was obtained.
The compositions of main components and the amount of accessory components, which are to be added, of the dielectric resonator thus produced are shown in Table 10, the electrode material which was used, the unloaded Q value and the bond strength are shown in Table 11. The resonant frequency is 1.3 to 1.7 GHz.
TABLE 10______________________________________ Composition of main component AccessorySam- (val- com-ple (molar fraction) ue) ponentNo. A B D x y z v u (wt. %)______________________________________188 Mg.sub.1/4 Nb Sn 0.340 0.520 0.130 0.010 0 Sr 0.100 Co.sub.1/4 Zn.sub.1/4 Ni.sub.1/4189 Mg.sub.1/3 Ta Sn 0.340 0.520 0.130 0.010 1.00 Sr 0.100 Co.sub.1/3 Ni.sub.1/3190 Mg.sub.1/4 Nb.sub.1/2 Sn 0.340 0.520 0.130 0.010 1.00 Sr 0.100 Co.sub.1/4 Ta.sub.1/2 Zn.sub.1/4 Ni.sub.1/4191 Mn Nb Sn 0.200 0.600 0.190 0.010 0 Ca 0.100192 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 0.500193 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ba 0.500194 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ca 0.500195 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Bi 0.500196 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Ba 0.500 Sr 0.500 Ca 0.500 Bi 0.500197 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 Cu 0.005198 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 Cu 0.100199 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 W 0.005200 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 W 0.100201 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 W 1.000202 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.000 W 2.000203 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.500204 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 1.500205 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 3.000206 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 7.000*207 Mg Nb Sn 0.300 0.400 0.200 0.100 1.00 Sr 8.000208 Mg Nb Hf 0.350 0.450 0.150 0.050 1.90 Sr 1.000209 Mg Nb Ge 0.350 0.450 0.150 0.050 1.90 Sr 1.000______________________________________
TABLE 11______________________________________Sample Electrode Bond strengthNo. material Qu (kg/4 mm.sup.2)______________________________________188 Cu 580 8.8189 Cu 540 6.1190 Cu 590 8.3191 Cu 480 5.1192 Cu 670 9.3193 Cu 600 9.1194 Cu 480 5.7195 Cu 540 8.7196 Cu 720 10.8197 Cu 760 12.0198 Cu 740 12.0199 Cu 730 10.9200 Cu 740 11.4201 Cu 700 9.7202 Cu 650 8.9203 Cu 760 10.8204 Ag 720 12.0205 Cu 720 11.1206 Cu 700 11.3*207 Cu 180 12.0208 Cu 630 10.1209 Cu 540 8.9______________________________________
As is apparent from the results shown in Table 11, the dielectric resonators of the embodiment had a high bond strength also when an electroless copper electrode is used in the same way as a silver electrode. For this reason, the unloaded Q value is high in a microwave frequency band and the resonant frequency can be prevented from deviating due to electrode peeling so that electric characteristics are stable. In addition, the dielectric resonators of the invention are suitable for forming electrodes by copper plating, so that they are suitable for large scale production and manufacturing costs can be reduced.
Additionally, a ZrTiO.sub.4 phase or one recognized as being a crystallographical ZrTiO.sub.4 phase was confirmed by powder X-ray diffraction of a dielectric ceramic within the composition range of Example 5. It was further confirmed in composition analysis by a local X-ray diffractometer of a fracture surface and polished surface of the dielectric ceramic having as the main component ZrTiO.sub.4 phase or crystallographical ZrTiO.sub.4 phase that all components of Zr, Ti, A, B and D (wherein A is at least one component selected from Mg, Co, Zn, Ni and Mn, B is at least one component selected from Nb and Ta, and D is at least one component selected from Sn, Hf and Ge) were present in a single grain, and their composition ratio was consistent with the composition ratio between other grains that constitute the main phase in the same dielectric ceramic. It was also confirmed that all components A, B and D blended were present in a single grain. Moreover, it was confirmed that a dielectric ceramic with components Zr, Ti, A, B and D present in a grain which constitutes the main phase showed a higher lattice constant in comparison with ZrTiO.sub.4 ceramics obtained under the same sintering conditions. Accordingly, it was confirmed that components A, B and D are substituted in the ZrTiO.sub.4 phase or the crystallographical ZrTiO.sub.4 phase.
Such dielectric ceramics specifically showed a high unloaded Q value and a high dielectric constant, and were superior in thermo-stability at a resonant frequency. The unloaded Q value was even higher when the molar ratio a/b of the component A to the component B was 0.5 or more and 1.9 or less. The dielectric resonators having such dielectric ceramics had an unloaded Q value which is specially high, and a high electrode bond strength.
As is apparent from the results described above, it was confirmed that the dielectric resonators of the example have the unloaded Q value which is especially high at a microwave frequency band. Moreover, the resonant frequency can be prevented from deviating due to electrode peeling. In addition, the dielectric resonators of the invention are suitable for forming electrodes by copper plating, so that they can be produced on a large scale and manufacturing costs can be reduced.
Although a dielectric ceramic having a cylindrical coaxial shape was used in Examples 4 and 5 of the invention, it is not limited to such a shape. For example, in the case of a TEM mode resonator using a dielectric ceramic having a prismatic coaxial or stepped coaxial shape, a microstrip line resonator using a dielectric resonator which has a planar shape, or a triplate resonator, an unloaded Q value which is equivalent to or more than the conventional ones can be obtained. Thus, a dielectric resonator in which stability is high and manufacturing costs are reduced can be obtained.
According to the structure of the dielectric ceramic of the invention, the variation in temperature coefficient at a resonant frequency due to heat history during sintering of ZrTiO.sub.4 and ZrO.sub.2 --SnO.sub.2 --TiO.sub.2 ceramics can be reduced. In addition, a high unloaded Q value is provided, and the temperature coefficient at a resonant frequency can be changed as desired without reducing the dielectric constant.
Furthermore, according to the structure of the dielectric resonator of the invention, a dielectric resonator having a high unloaded Q value and a strong electrode layer can be obtained.
The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not restrictive, the scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Number	Date	Country	Kind
6-288286	Nov 1994	JPX
7-294613	Nov 1995	JPX

Number	Name	Date
4665041	Higuchi et al.	May 1987
4785375	Campbell	Nov 1988
5084424	Abe et al.	Jan 1992
5132258	Takahashi et al.	Jul 1992
5264402	Sano et al.	Nov 1993
5322828	Sano et al.	Jun 1994
5356843	Okuyama et al.	Oct 1994
5470808	Okuyama et al.	Nov 1995
5948767	Ushida et al.	Aug 1990

Number	Date	Country
0 587 140	Mar 1994	EPX
2 581 639	May 1986	FRX
2 223 491	Dec 1973	DEX
39 15 339	May 1988	DEX
0017698	Feb 1977	JPX
02192460 A	Jul 1990	JPX

Dielectric ceramic compositions and dielectric resonators

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