Dielectric compositions for firing at low temperatures and electronic parts

Abstract

An object of the present invention is to provide a dielectric composition for firing at a low temperature having a high dielectric constant ∈ r, a high Q value, and a low temperature coefficient τ f of the resonance frequency. A dielectric composition for firing at low temperatures comprises a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3 (x+y+z 1+z 2+z 3+t=1 ; 0.070≦x≦0.300; 0.385≦y ≦0.844; 0.010≦z1≦0.130; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.075

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a low temperature-fired porcelain having a high dielectric constant ∈ r and to an electronic part using such porcelain.

[0004] 2. Related Art Statement

[0005] In high frequency circuit radio instruments such as cellular phones, top filters, interstage filters, local filters, etc. are used as high frequency circuit filters, and a laminated type dielectric filter is used as an interstage filter.

[0006] In order to produce a dielectric-laminated filter, a plurality of green sheets are produced from a powdery ceramic material to constitute a dielectric, and a given electrode pattern is formed on each of the green sheets by printing with a given conductive paste. A laminate is then obtained by laminating the resulting green sheets, and the laminate is fired so that the conductive paste layers and the green sheets are simultaneously fired to densify the laminate.

[0007] At that time a metallic conductor having a low melting point, such as a silver-based conductor, a copper-based conductor or a nickel-based conductor is generally used for the electrode. The melting points are, for example, 1100° C. or lower. Ag has a melting point of about 950to 960° C. For this reason, the dielectric needs to be sintered at a firing temperature lower than the melting point of the metal constituting the electrode.

[0008] The assignee has disclosed a dielectric composition for firing at a low temperature in Japanese patent publication H5-319922A.

SUMMARY OF THE INVENTION

[0009] It has recently been demanded to further miniaturize electronic parts and thus to further improve the dielectric constant ∈ r of a dielectric porcelain composition. For example, the lower limit of dimensions of a dielectric laminate filter obtainable is 2.0 mm×1.25 mm when the dielectric composition having a dielectric constant of 80. When a dielectric porcelain composition having a dielectric constant of 110 or higher is used, the lower limits of the dimensions of the filter can be reduced to 1.6 mm×0.8 mm.

[0010] An object of the present invention is to provide a dielectric composition for firing at a low temperature having a high dielectric constant ∈ r, a high Q value, and a low temperature coefficient τ f of resonance frequency.

[0011] A first aspect of the present invention provides a dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2. La2O3-z3.Sm2O3-t.Bi2O3 (x+y +z1+z2+z3+t=1; 0.070≦x≦0.300; 0.385≦y≦0.844; 0.010≦z1 ≦0.130; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.075<t≦0.185), and a glass component containing 0.1 weight percent or more of B2O3 in an amount of 0.05 to 20 weight parts with respect to 100 weight parts of the main composition.

[0012] A second aspect of the present invention further provides a dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.070≦x≦0.300; 0.385≦y≦0.844; 0.010≦z1≦0.130; 0.000≦z2 ≦0.120; 0.000≦z3≦0.120; 0.075<t≦0.185) and B2O3 in an amount of 0.05 to 10 weight parts with respect to 100 weight parts of the main composition.

[0013] The first and second aspects are the same in the main compositions.

[0014] A third aspect of the present invention provides a dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.100≦x≦0.250; 0.600≦y≦0.750; 0.010≦z1≦0.120; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.010≦(z1+z2+z3)≦0.120; 0.065≦t≦0.075; 0.35≦t/(z1+z2+z3+t), and a glass component containing 0.1 weight percent or more of B2O3 in an amount of 0.05 to 20 weight parts with respect to 100 weight parts of the main composition.

[0015] A fourth aspect of the present invention provides a dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3(x+y +z1+z2+z3+t=1; 0.100≦x≦0.250; 0.600≦y≦0.750 ; 0.010≦z1 ≦0.120; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.010≦(z1+z2+z3)≦0.120;0.065≦t≦0.075; 0.35≦t/(z1+z2+z3+t) and B2O3 in an amount of 0.05 to 10 weight parts with respect to 100 weight parts of the main composition.

[0016] The third and fourth aspects are the same in the main compositions.

[0017] The present invention further provides an electronic part having each of the dielectric compositions for firing at a low temperature according to the first to fourth aspects of the present invention.

[0018] The present invention provides a dielectric composition for firing at a low temperature having a high dielectric constant (∈ r), a high Q value, τ f (a low temperature coefficient of resonance frequency), and can be produced by firing at a low temperature. Typically, the dielectric constant ∈ r can be improved to 110 or more, Q can be improved to 200 or more, and the absolute value of τ f can be reduced to 50 or lower.

[0019] These and other objects, features and advantages of the invention will be appreciated upon reading the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the same could be made by the skilled person in the art.

Preferred Embodiments of the Invention

[0020] The main compositions are the same with each other in the first and second aspects of the invention, and will be described as follows.

[0021] The ratio “x” of BaO is made 0.070 or higher and 0.300 or lower in the main composition. The dielectric constant ∈ r can be improved by increasing “x” to 0.070 or higher. On the viewpoint, “x” is made 0.070 or higher and may preferably be 0.100 or higher. The “Q” value can be improved and τ f can be reduced by lowering “x” to 0.300 or lower. On the viewpoint, “x” is made 0.300 or lower, and may preferably be 0.250 or lower.

[0022] The ratio “y” of TiO2 is made 0.385 or higher and 0.844 or lower in the main composition. The “Q” value can be improved and τ f can be reduced by increasing “y” to 0.385 or higher. On the viewpoint, “y” is made 0.385 or higher, and may preferably be 0.390 or higher. The dielectric constant ∈ r can be improved by reducing “y” to 0.844 or lower. On the viewpoint, “y” is made 0.844 or lower and may preferably be 0.800 or lower.

[0023] The ratio “z1” of Nd2O3 is made 0.010 or higher and 0.130 or lower. The dielectric constant ∈ r can be improved by adjusting “z1” at a value in a range of 0.010 to 0.130. On the viewpoint, “z1” may preferably be 0.030 or higher and is 0.130 or lower.

[0024] The ratio “t” of Bi2O3 is made higher than 0.075 and 0.185 or lower in the main composition. The dielectric constant ∈ r can be improved by increasing “x” to a value exceeding 0.075. On the viewpoint, “t” may preferably be 0.0751 or higher and more preferably be 0.076 or higher. Further, the “Q” value can be improved and τ f can be reduced by lowering “t” to 0.185 or lower. On the viewpoint, “t” is made 0.185 or lower, and may preferably be 0.160 or lower.

[0025] The ratio “z2” of La2O3 is made 0.120 or lower. The dielectric constant ∈ r can be further improved by adding La2O3. Further, the “Q” value can be improved and τ f can be reduced by lowering “z2” to 0.120 or lower. On the viewpoint, “z2” is made 0.120 or lower, and may preferably be 0.100 or lower.

[0026] The ratio “z3” of Sm2O3 is made 0.120 or lower. The dielectric constant ∈ r and the “Q” value can be improved and τ f can be reduced by adding Sm2O3 in an amount of 0.120 or lower. On the viewpoint, “z3” is made 0.120 or lower, and may preferably be 0.100 or lower.

[0027] The main compositions are the same with each other in the third and fourth aspects of the invention, and will be described as follows.

[0028] The ratio “x” of BaO is made 0.100 or higher and 0.250 or lower in the main composition. The dielectric constant ∈ r can be improved by increasing “x” to 0.100 or higher. On the viewpoint, “x” may preferably be 0.150 or higher. The “Q” value can be improved and τ f can be reduced by lowering “x” to 0.250 or lower. On the viewpoint, “x” may preferably be 0.200 or lower.

[0029] The ratio “y” of TiO2 is made 0.600 or higher and 0.750 or lower in the main composition. The “Q” value can be improved and τ f can be reduced by increasing “y” to 0.600 or higher. On the viewpoint, “y” may preferably be 0.640 or higher. The dielectric constant ∈ r can be improved by reducing “y” to 0.750 or lower. On the viewpoint, “y” may preferably be 0.720 or lower.

[0030] The ratio “z1” of Nd2O3 is made 0.010 or higher and 0.120 or lower. The dielectric constant ∈ r can be improved by reducing “z1” to 0.120 or lower. τ f can be reduced by increasing “z1” to 0.010 or higher. “z1” may preferably be 0.030 or higher.

[0031] The ratio “z2” of La2O3 is made 0.120 or lower. The dielectric constant ∈ r can be further improved by adding La2O3. The “Q” value can be improved and τ f can be reduced by reducing “z2” to 0.120 or lower.

[0032] The ratio “z3” of Sm2O3 is made 0.120 or lower. The “Q” value and the dielectric constant ∈ r can be improved and τ f can be reduced by adding Sm2O3 in an amount of 0.120 or lower.

[0033] (z1+z2+z3) is made 0.010 or higher and 0.120 or lower, so that the dielectric constant ∈ r can be improved.

[0034] The ratio “t” of Bi2O3 is made 0.065 or higher and 0.075 or lower in the main composition. It is found that the dielectric constant ∈ r can be improved only when t/(z1+z2+z3) is 0.35 or higher, provided that “t” is 0.75 or lower. It is further found that the Q value is lowered when “t” is lower than 0.065, provided that t/(z1+z2+z3) is 0.35 or higher. It is also found that the dielectric constant ∈ r is reduced when t/(z1+z2+z3) is lower than 0.35, provided that “t” is in a range of 0.065 to 0.075.

[0035] According to the first and third aspects of the present invention, a glass component containing 0.1 weight percent or more of B2O3 is mixed to the main composition in an amount of 0.05 to 20 weight parts with respect to 100 weight parts of the main composition. The porcelain can be obtained by sintering at a low temperature by adding 0.1 weight percent or more of B2O3 into the glass component.

[0036] The content of the glass component is made 0.05 weight parts or higher, so that the dielectric constant ∈ r of the porcelain can be further improved. On the viewpoint, the content of the glass component is made 0.05 weight parts or higher and may preferably be 0.10 weight parts or higher. Further, the dielectric constant ∈ r can be improved by reducing the content of the glass component to 20.0 weight parts or lower. On the viewpoint, the content of the glass component is made 20.00 weight parts or lower, and may preferably be 15.00 weight parts or lower.

[0037] The glass component is not particularly limited and may preferably be one or more of the followings.

[0038] ZnO—B2O3—SiO2, ZnO—Bi2O3—B2O3—SiO2, B2O3—SiO2RO—B2O3—SiO2 (R represents an alkali earth metal) GeO2—B2O3 GeO2—B2O3 —SiO2 GeO2—ZnO—B23—SiO2 GeO2—ZnO—B2O3 Li2O—Al2O3—SiO2—B2O3 Li2O—Al2O3—SiO2—ZnO—B2O3 RO—Li2O—Al2O3—SiO2—B2O3 (R represents an alka earth metal) RO—Li2O—Al2O3—SiO2—ZnO—B2O3 (R represents an alkali earth metal) Re2O—B2O3—SiO2 (Re represents an alkali metal) Re2O—B2O3—ZnO—SiO2 (Re represents an alkali metal), Re2O—RO—B2O3—SiO2 glass (Re represents an alkali metal and R represents an alkali earth metal), and Re2O—RO—B2O3—ZnO—SiO2 glass (Re represents an alkali metal and R represents an alkali earth metal)

[0039] In a preferred embodiment, the glass component has a composition of ZnO—B2O3—SiO2 where k(weight %) ZnO.m(weight %) B2O3.n(weight %) SiO2 (10≦k≦85, 5≦m≦50, 2≦n≦60; k+m+n=100).

[0040] In the above composition, the vitrifaction of the composition can be proceeded by increasing the content (k) of ZnO to 10 weight percent or higher. On the viewpoint, “k” is made 10 weight percent or higher and may preferably be 20 weight percent or higher. Further, the vitrifaction of the composition can be proceeded and the optimum firing temperature of the dielectric porcelain composition can be reduced by increasing “k” to 85 weight percent or higher. On the viewpoint, “k” is made 85 weight percent or lower, and may preferably be 80 weight percent or lower.

[0041] The vitrifaction of the composition can be proceeded and the dielectric constant ∈ r can be improved by increasing the content (m) of B2O3 to 5 weight percent or higher. On the viewpoint, “m” is made 5 weight percent or higher, and may preferably be 10 weight percent or higher. Further, Q can be reduced by lowering “m” to 50 weight percent or lower. On the viewpoint, “m” is made 50 weight percent or lower, and may preferably be 45 weight percent or lower.

[0042] A glass having stable properties can be produced by adding SiO2 in a content “n” of 2 weight percent or higher. On the viewpoint, “n” may preferably be 5 weight percent or higher. On the other hand, the vitrifaction of the composition can be proceeded and sintering temperature of the dielectric porcelain composition can be reduced by adding SiO2 in a content “n” of 60 weight percent or lower.

[0043] According to the second and fourth aspects of the present invention, 0.05 weight parts or higher and 10 weight parts or lower of B2O3 is added in the main composition with respect to 100 weight parts of the main composition. The dielectric constant ∈ r and Q value can be improved by adding B2O3 in a content of 0.05 weight parts or higher. On the viewpoint, the content of B2O3 is made 0.05 weight parts or higher, and may preferably be 0.1 weight parts or higher. Further, the dielectric constant ∈ r and Q value can be improved by adding B2O3 in a content of 10 weight parts or lower, and may preferably be 9 weight parts or lower.

[0044] In the first to fourth aspects of the present invention, each of the ratios “x”, “y”, “z1”, “z2”, “z3” and “t” of the metal oxide components is a converted value of a content of each metal contained in the corresponding raw material calculated as a content of the metal oxide. The converted value of the content of each metal in a mixture of the raw materials is dependent on a mixed ratio of the raw materials. According to the present invention, the mixed ratio of the raw materials for metals is weighed using a precision balance to obtain a measured ratio, so that the converted contents are then calculated based on the measured ratio.

[0045] The main compositions and glass components of the dielectric porcelain compositions according to the first to fourth aspects of the invention has been described above. The other metal element or elements may be contained in the compositions.

[0046] For example, the dielectric composition may contain one or more metal selected from the group consisting of Ag, Cu and Ni in a total amount of 5 weight percent or lower. It is thus possible to further reduce τ f.

[0047] The dielectric composition may contain one or more metal oxide selected from the group consisting of CuO, V2O5 and WO3. In this case, a total content of the metal oxides may preferably be 0.0 to 5.0 weight percent.

[0048] The dielectric composition may further contain at lease one of the oxides of Mg, Al, Si, Ca, Sc, Fe, Co, Ni, Zn, Ga, Se, Sr, Y, Zr, Nb, Mo, Ru, Hf and Mn in a total content of 5 weight percent or lower.

[0049] The materials for a metal electrode used in the electronic part according to the invention is not particularly limited. Such material may preferably be silver, copper, nickel, or the alloys of these metals, more preferably be silver or the alloy of silver, and most preferably be silver.

[0050] The electronic parts targeted by the first to fourth aspects of the present invention are not particularly limited, but laminated dielectric filters, multi-layered circuit boards, dielectric antennas, dielectric couplers, dielectric composite modules, bulk type dielectric filters etc. are recited by way of example.

[0051] The dielectric composition for firing at a low temperature may be sintered at a temperature of 1100° C. or lower, more preferably be 1050° C. or lower, and most preferably 1000° C. or lower.

[0052] The porcelains according to the first to fourth aspects of the present invention may preferably be produced as follows. Starting materials for the respective metal components are mixed in a given ratio to obtain a mixed powder. The powder is then calcined at 1000 to 1400° C. to obtain a calcined powder, which is then crushed to obtain ceramic powder. Preferably, a green sheet is formed by using the ceramic powder and a glass powder composed of SiO2, B2O3 and ZnO, and the green sheet is fired at 850 to 930° C. As the starting materials for the respective metallic oxide components, an oxide, a nitrate, a carbonate, a sulfate or the like of each of the metals may be used.

EXAMPLES

Experiment 1

[0053] (Production of Powder of the Main Composition)

[0054] Powdery raw materials of barium carbonate, titanium oxide, neodymium oxide, bismuth oxide, lanthanum oxide and samarium oxide each having a high purity were weighed in given ratios shown in tables 2, 3 and 4 to obtain mixed powder. The mixed powder was charged into a polyethylene pot with alumina medium and water was added to wet mix the powder. The thus obtained mixture was drawn from the pot, dried, and charged into an alumina crucible to calcine the mixture at various temperatures of 900 to 1270° C. for 4 hours under air to obtain a calcined body.The calcined body was crushed, charged into a polyethylene pot with zirconia medium and ground until the mean grain diameter is reduced to 0.1 to 2.0 μm measured by laser diffraction scattering method to obtain various kinds of calcined and crushed compositions.

[0055] (Production of Glass Powder)

[0056] Powdery raw materials of zinc oxide, boron oxide and silicon oxide each having a high purity were weighed according to ratios shown in table 1 and mixed to obtain mixed powder. The mixed powder was then charged into a polyethylene pot with alumina medium and dry mixed. The thus obtained mixture was molten in a chamotte crucible, and rapidly cooled by immersing it into water to proceed the vitrifaction. The thus obtained glass was charged in an alumina pot with alumina medium and then ground until the mean grain diameter is reduced to 4 μm in ethanol to obtain each glass powder shown in table 1.

	TABLE 1
	Glass
	Composition No.	ZnO	B2O3	SiO2
	A1	0.10	0.45	0.45
	A2	0.20	0.40	0.40
	A3	0.50	0.29	0.21
	A4	0.70	0.15	0.15
	A5	0.80	0.10	0.10
	A6	0.85	0.05	0.10
	A7	0.60	0.05	0.35
	A8	0.40	0.10	0.50
	A9	0.20	0.20	0.60
	A10	0.35	0.30	0.35
	A11	0.15	0.45	0.40
	A12	0.20	0.50	0.30
	A13	0.75	0.23	0.02
	A14	0.45	0.50	0.05
	A15	0.30	0.40	0.30
	A16	0.30	0.20	0.50
	A17	0.25	0.20	0.55
	A18	0.35	0.05	0.60

[0057] (Production of Porcelain)

[0058] The main composition powder and glass powder as described above were formulated as shown in tables 2 to 4. The formulates were charged in a polyethylene pot with alumina medium and water was added for wet mixing. 1 weight percent, of polyvinyl alcohol was added as a binder to the mixture with respect to a total weight of the powder of the main component and glass powder. The thus obtained mixture was dried and passed through a sieve having a mesh diameter of 355 μm and granulated. “Glass contents” shown in tables 2, 3 and 4 were the contents of the glass component with respect to 100 weight parts of the main composition.

[0059] The thus obtained granulated powder was shaped using a press molding machine at a bearing stress of 1 ton/cm2 to obtain a disk shaped test piece having a diameter φ of 20 mm and a thickness of 15 mm. The thus obtained test piece was sintered for 2 hours at 900° C. in air to produce various samples of the dielectric porcelains. Further, the thus sintered samples were ground to a disk having a diameter φ of 16 mm and a thickness of 8 mm, and the dielectric properties were measured. The dielectric constant (∈ r) and Q were measured by parallel conductor type dielectric resonator method, and the temperature coefficient (τ f) of resonance frequency was measured in a range of −25° C. to 75° C. The measurements were performed at a frequency of 2 to 4 GHz. The results were shown in tables 2, 3 and 4.

TABLE 2
Main							Glass
composition		y:	z1:	t:	z2:	z3:	Composition	Content
No.	x: BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of glass	εr	Q(at3 GHz)	τf
B1	0.050	0.797	0.063	0.090	0.000	0.000	A3	2.5 wt %	108	357	36
B2	0.070	0.800	0.053	0.077	0.000	0.000	A3	2.5 wt %	110	405	28
B3	0.100	0.752	0.070	0.078	0.000	0.000	A3	2.5 wt %	113	380	30
B4	0.200	0.660	0.060	0.080	0.000	0.000	A3	2.5 wt %	124	242	37
B5	0.250	0.620	0.051	0.079	0.000	0.000	A3	2.5 wt %	128	236	39
B6	0.300	0.600	0.024	0.076	0.000	0.000	A3	2.5 wt %	130	230	41
B7	0.320	0.584	0.020	0.076	0.000	0.000	A3	2.5 wt %	150	124	256
B8	0.423	0.380	0.097	0.100	0.000	0.000	A3	2.5 wt %	149	153	67
B9	0.300	0.385	0.130	0.185	0.000	0.000	A3	2.5 wt %	143	205	48
B10	0.300	0.390	0.130	0.180	0.000	0.000	A3	2.5 wt %	141	209	47
B11	0.146	0.584	0.120	0.150	0.000	0.000	A3	2.5 wt %	135	221	44
B12	0.200	0.600	0.110	0.090	0.000	0.000	A3	2.5 wt %	136	218	46
B13	0.120	0.750	0.050	0.080	0.000	0.000	A3	2.5 wt %	118	310	33
B14	0.071	0.800	0.053	0.076	0.000	0.000	A3	2.5 wt %	111	409	29
B15	0.070	0.844	0.011	0.075	0.000	0.000	A3	2.5 wt %	110	410	28
B16	0.064	0.850	0.010	0.076	0.000	0.000	A3	2.5 wt %	89	430	25

[0060]

TABLE 3
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of Glass	εr	Q(at3 GHz)	τf
B17	0.194	0.724	0.005	0.077	0.000	0.000	A3	2.5 wt %	113	175	63
B18	0.180	0.700	0.010	0.110	0.000	0.000	A3	2.5 wt %	126	238	39
B19	0141	0.750	0.030	0.079	0.000	0.000	A3	2.5 wt %	120	249	35
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	2.5 wt %	123	245	37
B21	0.170	0.570	0.110	0.150	0.000	0.000	A3	2.5 wt %	132	226	42
B22	0.190	0.600	0.130	0.080	0.000	0.000	A3	2.5 wt %	124	242	37
B23	0.153	0.623	0.140	0.084	0.000	0.000	A3	2.5 wt %	106	262	29
B25	0160	0.695	0.0698	0.0752	0.000	0.000	A3	2.5 wt %	110	300	28
B26	0.160	0.695	0.0695	0.0755	0.000	0.000	A3	2.5 wt %	115	28	30
B27	0.160	0.695	0.069	0.076	0.000	0.000	A3	2.5 wt %	120	260	34
B28	0.180	0.660	0.083	0.077	0.000	0.000	A3	2.5 wt %	122	247	36
B29	0.171	0.640	0.089	0.100	0.000	0.000	A3	2.5 wt %	134	222	43
B30	0.170	0.580	0.090	0.160	0.000	0.000	A3	2.5 wt %	142	208	48
B31	0.165	0.600	0.050	0.185	0.000	0.000	A3	2.5 wt %	143	205	49
B32	0.154	0.580	0.076	0.190	0.000	0.000	A3	2.5 wt %	147	183	58

[0061]

TABLE 4
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of Glass	εr	Q(at3 GHz)	τf
B33	0.150	0.720	0.030	0.090	0.000	0.010	A3	2.5 wt %	129	232	41
B34	0.140	0.690	0.040	0.100	0.020	0.010	A3	2.5 wt %	128	234	42
B35	0.170	0.660	0.020	0.080	0.050	0.020	A3	2.5 wt %	132	225	42
B36	0.160	0.570	0.040	0.080	0.100	0.050	A3	2.5 wt %	132	225	42
B37	0.200	0.490	0.030	0.100	0.120	0.060	A3	2.5 wt %	142	208	47
B38	0.125	0.537	0.052	0.076	0.140	0.070	A3	2.5 wt %	151	126	89
B39	0.120	0.680	0.090	0.100	0.010	0.000	A3	2.5 wt %	118	310	33
B40	0.170	0.590	0.080	0.130	0.010	0.020	A3	2.5 wt %	140	211	48
B41	0.180	0.600	0.050	0.090	0.030	0.050	A3	2.5 wt %	128	245	40
B42	0.090	0.610	0.030	0.100	0.070	0.100	A3	2.5 wt %	118	305	33
B43	0.070	0.550	0.040	0.120	0.100	0.120	A3	2.5 wt %	129	239	40
B44	0.120	0.495	0.096	0.079	0.070	0.140	A3	2.5 wt %	105	290	39

[0062] As shown in table 2, the dielectric constant ∈ r can be improved by increasing the ratio “x” of BaO to 0.070 or higher. Further, the Q value can be improved and τ f can be reduced by lowering “x” to 0.300 or lower.

[0063] As shown in table 2, the Q value can be improved and τ f can be reduced by increasing the ratio “y” of TiO2 to 0.385 or higher. Further the dielectric constant ∈ r can be improved by reducing “y” to 0.844 or lower.

[0064] As shown in table 3, the dielectric constant ∈ r can be improved by increasing the ratio “z1” of Nd2O3 to 0.010 to 0.130.

[0065] As shown in table 3, the dielectric constant ∈ r can be improved by increasing the ratio “t” of Bi2O3 to a value exceeding 0.075. Further the Q value can be improved and τ f can be reduced by lowering “t” to 0.185 or lower.

[0066] As shown in table 4, the dielectric constant ∈ r can be further improved by adding La2O3. Further, the Q value can be improved and τ f can be reduced by reducing “z2” to 0.120 or lower.

[0067] As shown in table 4, the dielectric constant ∈ r and the Q value can be improved and τ f can be reduced by adding Sm2O3 in an amount of 0.120 or lower.

Experiment 2

[0068] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. Compositions A1 to A18 of the glass components were shown in table 1. The ratios of the metal elements and glass compositions were shown in tables 5 and 6. The results obtained by using the glass compositions A1 to A14 were shown in table 5, and the results obtained by using the glass compositions A15 to A18 were shown in table 6.

TABLE 5
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of Glass	εr	Q(at3 GHz)	τf
B4	0.200	0.660	0.060	0.080	0.000	0.000	A1	2.5 wt %	128	232	40
B12	0.200	0.600	0.110	0.090	0.000	0.000	A2	2.5 wt %	130	230	41
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	2.5 wt %	123	245	37
B28	0.180	0.660	0.085	0.075	0.000	0.000	A4	2.5 wt %	122	245	40
B35	0.170	0.660	0.020	0.080	0.050	0.020	A5	2.5 wt %	125	242	39
B41	0.180	0.600	0.050	0.090	0.030	0.050	A6	2.5 wt %	129	234	40
B4	0.200	0.660	0.060	0.080	0.000	0.000	A7	2.5 wt %	125	245	38
B12	0.200	0.600	0.110	0.090	0.000	0.000	A8	2.5 wt %	124	243	37
B20	0170	0.684	0.070	0.076	0.000	0.000	A9	2.5 wt %	122	246	37
B28	0.180	0.660	0.085	0.075	0.000	0.000	A10	2.5 wt %	123	244	37
B35	0.170	0.660	0.020	0.080	0.050	0.020	A11	2.5 wt %	125	241	38
B41	0.180	0.600	0.050	0.090	0.030	0.050	A12	2.5 wt %	124	242	37
B4	0.200	0.660	0.060	0.080	0.000	0.000	A13	2.5 wt %	124	243	38
B12	0.200	0.600	0.110	0.090	0.000	0.000	A14	2.5 wt %	126	238	39

[0069]

TABLE 6
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of Glass	εr	Q(at3 GHz)	τf
B20	0.170	0.684	0.070	0.076	0.000	0.000	A15	2.5 wt %	124	242	37
B28	0.180	0.660	0.085	0.075	0.000	0.000	A16	2.5 wt %	122	252	36
B35	0.170	0.660	0.020	0.080	0.050	0.020	A17	2.5 wt %	121	248	37
B41	0.180	0.600	0.050	0.090	0.030	0.050	A18	2.5 wt %	120	250	34
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	0.01 wt %	82	120	59
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	0.05 wt %	115	330	31
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	0.10 wt %	118	295	34
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.00 wt %	120	248	35
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	2.50 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	5.00 wt %	123	246	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	10.00 wt %	120	245	36
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	15.00 wt %	115	329	33
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	20.00 wt %	110	290	29
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	25.00 wt %	91	200	31

[0070] As can be seen from tables 5 and 6, the dielectric constant ∈ r and Q values can be improved and τ f can be reduced by using the glass compositions according to the present invention.

Experiment 3

[0071] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. The glass composition A3 was used and the ratio or the ingredients was changed as shown in table 6. As can be seen from the results, the dielectric constant ∈ r and Q values can be improved and τ f can be reduced by adjusting the glass content to 0.05 to 20.00 weight percent.

Experiment 4

[0072] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. The glass composition was changed as shown in table 7 and the ratio of metal oxides and glass composition were changed as shown in table 8. As can be seen from the results, the dielectric constant ∈ r and Q values can be improved and τ f can be reduced in a range of the present invention.

TABLE 7
Composition No. Composition system
A19             ZnO—B2O3—SiO2 glass
A20             ZnO—Bi2O3—B2O3—SiO2 glass
A21             B2O3—SiO2 glass
A22             RO—B2O3—SiO2 glass
                (R represents an alkali earth metal)
A23             GeO2—B2O3 glass
A24             GeO2—B2O3—SiO2 glass
A25             GeO2—ZnO—B2O3—SiO2 glass
A26             GeO2—ZnO—B2O3 glass
A27             Li2O—Al2O3—SiO3—B2O3 glass
A28             Li2O—Al2O3—SiO3—ZnO—B2O3 glass
A29             RO—Li2O—Al2O3—SiO3—B2O3 glass
                (R represents an alkali earth metal)
A30             RO—Li2O—Al2O3—SiO3—ZnO—B2O3 glass
                (R represents an alkali earth metal)
A31             Re2O—B2O3—SiO2 glass
                (Re represents an alkali metal)
A32             Re2O—B2O3—ZnO—SiO2 glass
                (Re represents an alkali metal)
A33             Re2O—RO—B2O3—SiO2 glass
                (Re represents an alkali metal:
                R represents an alkali earth metal)
A34             Re2O—RO—B2O3—ZnO—SiO2 glass
                (Re represents an alkali metal;
                R represents an alkali earth metal)

[0073]

TABLE 8
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of glass	εr	Q(at3 GHz)	τf
B20	0.170	0.684	0.070	0.076	0.000	0.000	A19	2.5 wt %	126	239	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A20	2.5 wt %	124	243	36
B20	0.170	0.684	0.070	0.076	0.000	0.000	A21	2.5 wt %	125	242	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A22	2.5 wt %	126	237	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A23	2.5 wt %	126	239	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A24	2.5 wt %	123	248	36
B20	0.170	0.684	0.070	0.076	0.000	0.000	A25	2.5 wt %	125	239	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A26	2.5 wt %	126	243	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A27	2.5 wt %	127	231	40
B20	0.170	0.684	0.070	0.076	0.000	0.000	A28	2.5 wt %	129	230	40
B20	0.170	0.684	0.070	0.076	0.000	0.000	A29	2.5 wt %	128	238	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A30	2.5 wt %	124	241	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A31	2.5 wt %	123	246	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A32	2.5 wt %	125	240	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A33	2.5 wt %	126	239	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A34	2.5 wt %	128	231	40

Experiment 5

[0074] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. Bi2O3 was added as the glass component and the content was changed as shown in table 9. The composition of the metal oxides was also changed as shown in table 9. As a result, the dielectric constant ∈ r and Q values can be improved and τ f can be reduced by adding 0.01 weight percent or more of Bi2O3.

TABLE 9
Main							Glass
Composition	x:	y:	z1:	t:	z2:	z3:	Composition	Content
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	No.	of glass	εr	Q(at3 GHz)	τf
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	0.01 wt %	110	205	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	0.10 wt %	116	212	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.00 wt %	120	226	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	2.50 wt %	126	239	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	5.00 wt %	125	242	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	10.00 wt %	121	238	38

Experiment 6

[0075] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. The glass composition A3 was used in a content of 1.5 weight percent. The ratio of metal oxides was changed as shown in table 10. Silver, copper and nickel was added to the main component as shown in table 10.

TABLE 10
Main
Compo-										Content of		Q
sition	x:	y:	Z1:	t:	z2:	z3:	Glass	Content	Additional	Additional		(at 3
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	Composition	of glass	Component	Component	εr	GHz)	τf
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ag	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ag	0.5 wt %	126	230	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ag	2.5 wt %	124	220	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ag	5.0 wt %	120	210	35
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ag	7.5 wt %	109	190	63
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Cu	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Cu	0.5 wt %	126	230	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Cu	2.5 wt %	125	220	34
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Cu	5.0 wt %	122	205	32
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Cu	7.5 wt %	108	188	62
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ni	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ni	0.5 wt %	126	235	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ni	2.5 wt %	125	220	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ni	5.0 wt %	122	210	36
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	Ni	7.5 wt %	109	189	63

[0076] As a result, the dielectric constant ∈ r and Q value can be improved and τ f can be reduced when silver, copper or nickel was added to the main composition.

Experiment 7

[0077] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. The glass composition A3 was used in a content of 1.5 weight percent. The ratio of metal oxides was changed as shown in table 10. Copper oxide, vanadium oxide or tungsten oxide was added to the main component as shown in table 11.

TABLE 11
Main
Compo-										Content of		Q
nent	x:	y:	Z1:	t:	z2:	z3:	Glass	Content	Additional	Additional		(at 3
No.	BaO	TiO2	Nd2O3	Bi2O3	La2O3	Sm2O3	Composition	of glass	Component	Component	εr	GHz)	τf
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	CuO	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	CuO	0.5 wt %	126	320	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	CuO	2.5 wt %	125	270	38
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	CuO	5.0 wt %	123	230	36
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	CuO	7.5 wt %	107	168	10
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	V2O5	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	V2O5	0.5 wt %	128	290	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	V2O5	2.5 wt %	126	250	39
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	V2O5	5.0 wt %	124	220	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	V2O5	7.5 wt %	105	143	68
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	WO3	0.0 wt %	123	245	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	WO3	0.5 wt %	130	240	41
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	WO3	2.5 wt %	127	230	40
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	WO3	5.0 wt %	125	210	37
B20	0.170	0.684	0.070	0.076	0.000	0.000	A3	1.5 wt %	WO3	7.5 wt %	107	183	67

[0078] As a result, the dielectric constant ∈ r and Q value can be improved and τ f can be reduced when copper oxide, vanadium oxide or tungsten oxide was added to the main composition.

Experiment 8

[0079] Porcelains were produced according to the same process as the experiment 1 and the properties were measured as the experiment 1. The glass composition A3 was used in a content of 2.5 weight percent. The ratio of metal oxides was changed as shown in tables 12 and 13. The results were shown in tables 12 and 13.

TABLE 12
Main
Compo-							z1 +			Glass	Content		Q	τf
sition		x:	y:	Z1:	z2:	z3:	Z2 +		t:	Composition	of Glass		(at	ppm/
No.		BaO	TiO2	Nd2O3	La2O3	Sm2O3	Z3	a	Bi2O3	No.	(wt, %)	εr	3 GHz)	° C.
C1	Comparative	0.090	0.750	0.088	0.000	0.000	0.088	0.450	0.072	A3	2.5	107	305	23
	Example
C2	Example	0.137	0.680	0.110	0.000	0.000	0.110	0.400	0.073	A3	2.5	112	295	34
C3	Example	0.176	0.660	0.090	0.000	0.000	0.090	0.450	0.074	A3	2.5	126	278	38
C4	Example	0.160	0.715	0.050	0.000	0.000	0.050	0.600	0.075	A3	2.5	130	259	41
C5	Example	0.245	0.657	0.030	0.000	0.000	0.030	0.695	0.068	A3	2.5	132	227	49
C6	Example	0.245	0.657	0.030	0.000	0.000	0.030	0.695	0.068	A3	2.5	138	213	54
C7	Comparative	0.260	0.600	0.080	0.000	0.000	0.080	0.427	0.060	A3	2.5	123	190	60
	Example
C8	Comparative	0.226	0.580	0.120	0.000	0.000	0.120	0.380	0.074	A3	2.5	122	194	54
	Example
C9	Comparative	0.100	0.770	0.065	0.000	0.000	0.065	0.500	0.065	A3	2.5	108	297	27
	Example

[0080]

TABLE 13
Main										Glass	Content		Q	τf
Composition		x:	y:	z1:	z2:	z3:	z1 + z2 +		t:	Composition	Of glass		(at	ppm/
No.		BaO	TiO2	Nd2O3	La2O3	Sm2O3	Z3	a	Bi2O3	No.	wt. %	εr	3 GHz)	° C.
C10	Comparative	0.180	0.620	0.130	0.000	0.000	0.130	0.350	0.070	A3	2.5	106	227	44
	Example
C11	Comparative	0.225	0.704	0.005	0.000	0.000	0.005	0.930	0.066	A3	2.5	112	224	96
	Example
C12	Comparative	0.200	0.720	0.056	0.000	0.000	0.056	0.300	0.024	A3	2.5	106	248	30
	Example
C13	Example	0.116	0.730	0.080	0.000	0.000	0.080	0.480	0.074	A3	2.5	112	282	28
C14	Example	0.167	0.666	0.020	0.080	0.000	0.100	0.400	0.067	A3	2.5	117	244	39
C15	Example	0.175	0.650	0.030	0.000	0.070	0.100	0.430	0.075	A3	2.5	127	241	43
C16	Example	0.215	0.630	0.020	0.020	0.050	0.090	0.420	0.065	A3	2.5	122	213	50
C17	Comparative	0.205	0.707	0.000	0.022	0.000	0.022	0.750	0.066	A3	2.5	124	237	72
	Example
C18	Comparative	0.185	0.668	0.080	0.015	0.015	0.110	0.250	0.037	A3	2.5	105	240	33
	Example

[0081] In the composition No. C1, the ratio “x” of BaO was low so that the dielectric constant ∈ r was reduced. In composition numbers C2 to C6, the dielectric constant ∈ r and Q can be improved and the temperature coefficient (τ f ) of resonance frequency can be maintained at a low value. In number C7, the ratio “x” of BaO was large and the ratio “t” of Bi2O3 was low so that Q can be reduced. In number C8, the ratio “y” of TiO2 was low so that Q was lowered. In number C9, the ratio “y” of TiO2 was high, so that the dielectric constant ∈ r was reduced. In number C10, (z1+z2+z3) was high so that the dielectric constant ∈ r was lowered. In number C11, the ratio “z1” of Nd2O3 was low so that the temperature coefficient (τ f) of resonance frequency was large. In number C12, a/(z1+z2+z3) was low and the ratio “t” of Bi2O3 was low, so that the dielectric constant ∈ r was reduced. In numbers C13 to C16, the dielectric constant ∈ r and Q can be improved and the temperature coefficient (τ f) of resonance frequency can be maintained at a low value. In number C17, the ratio “z1” of Nd2O3 was low so that the temperature coefficient (τ f) of resonance frequency was large. In number C18, a/(z1+z2+z3) and the ratio “t” of Bi2O3 were low, so that the dielectric constant ∈ r was lowered.

[0082] As described above, the present invention provides a dielectric composition for firing at a low temperature having a high dielectric constant ∈ r, a high Q value and a low temperature coefficient τ f of resonance frequency.

[0083] The present invention has been explained referring to the preferred embodiments, however, the present invention is not limited to the illustrated embodiments which are given by way of examples only, and may be carried out in various modes without departing from the scope of the invention.

Claims

1. A dielectric composition for firing at low temperatures comprising a main composition of x.BaO—y.TiO2-z1.Nd2O3-z2.La2O3 —z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.070≦x≦0.300; 0.385≦-y≦0.844; 0.010≦z1≦0.130; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.075≦t≦0.185), and a glass component containing 0.1 weight percent or more of B2O3 in an amount of 0.05 to 20 weight parts with respect to 100 weight parts of said main composition.

2. The dielectric composition of claim 1, wherein said glass component is selected from the group consisting of the following compositions. ZnO—B2O3—SiO2 ZnO—Bi2O3—B2O3—SiO2 B2O3—SiO2 RO—B2O3—SiO2 (R represents an alkali earth metal) GeO2—B2O3 GeO2—B2O3 —SiO2 GeO2—ZnO—B2O3—SiO2 GeO2—ZnO—B2O—Li2O—Al2O3—SiO2—B2O3 Li2O—Al2O3—SiO2—ZnO—B2O3 RO—Li2O—Al2O3—SiO2—B2O3 (R represents an alkali earth metal) RO—Li2O—Al2O3—SiO2—ZnO—B2O3 (R represents an alkali earth metal) Re2O—B2O3—SiO2 (Re represents an alkali metal) Re2O—B2O3—ZnO—SiO2 (Re represents an alkali metal) Re2O—RO—B2O3—SiO2 glass (Re represents an alkalimetal and R represents an alkali earth metal) and Re2O—RO—B2O3—ZnO—SiO2 glass (Re represents an alkali metal and R represents an alkali earth metal)

3. The dielectric composition of claim 2, wherein said glass component comprises a glass component of ZnO—B2O3—SiO2 having a composition of k (weight %) ZnO.m(weight %) B2O3.n (weight %) SiO2(10≦k≦85, 5≦m≦50, 2≦n≦60; k+m+n=100).

4. The dielectric composition of claim 1, comprising one or more metal element selected from the group consisting of Ag, Cu and Ni in a total amount of 5 weight percent or lower.

5. The dielectric composition of claim 1, comprising one or more metal oxide selected from the group consisting of CuO, V2O5 and WO3.

6. An electronic part comprising said dielectric composition of claim 1.

7. The electronic part of claim 6 being a laminate type dielectric filter

8. A dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.070≦x ≦0.385≦y≦0.844; 0.010≦z1≦0.130; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.075≦t≦0.185) and B2O3 in an amount of 0.05 to 10 weight parts with respect to 100 weight parts of said main composition.

9. The dielectric composition of claim 8, comprising one or more metal element selected from the group consisting of Ag, Cu and Ni in a total amount of 5 weight percent or lower.

10. The dielectric composition of claim 8, comprising one or more metal oxide selected from the group consisting of CuO, V2O5 and WO3.

11. An electronic part comprising said dielectric composition of claim 8.

12. The electronic part of claim 11 being a laminate type dielectric filter

13. A dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3-z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.100≦x≦0.250; 0.600≦y≦0.750; 0.010≦z1≦0.120; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.010≦(z1+z2+z3)≦0.120; 0.065≦t≦0.075; 0.35≦t/(z1+z2+z3+t), and a glass component containing 0.1 weight percent or more of B2O3 in an amount of 0.05 to 20 weight parts with respect to 100 weight parts of said main composition.

14. The dielectric composition of claim 13, wherein said glass component is selected from the group consisting of the following compositions. ZnO—B2O3—SiO2 ZnO—Bi2O3—B2O3—SiO2 B2O3—SiO2 RO—B2O3—SiO2 (R represents an alkali earth metal) GeO2—B2O3 GeO2—B2O3—SiO2 GeO2—ZnO—B2O3—SiO2 GeO2—ZnO—B2O3 Li2O—Al2O3—SiO2—B2O3 Li2O—Al2O3—SiO2—ZnO—B2O3 RO—Li2O—Al2O3—SiO2—B2O3 (R represents an alkali earth metal) RO—Li2O—Al2O3—SiO2—ZnO—B2O3 (R represents an alkali earth metal) Re2O—B2O3—SiO2 (Re represents an alkali metal) Re2O—B2O3—ZnO—SiO2 (Re represents an alkali metal) Re2O—RO—B2O3—SiO2 glass (Re represents an alkali metal and R represents an alkali earth metal) and Re2O—RO—B2O3—ZnO—SiO2 glass (Re represents an alkali metal and R represents an alkali earth metal)

15. The dielectric composition of claim 14, wherein said glass component comprises a glass component of ZnO—B2O3—SiO2 having a composition of k (weight %) ZnO .m(weight %) B2O3. n(weight %) SiO2 (10≦k≦85, 5≦m≦50, 2≦n≦60; k+m+n=100).

16. The dielectric composition of claim 13, comprising one or more metal element selected from the group consisting of Ag, Cu and Ni in a total amount of 5 weight percent or lower.

17. The dielectric composition of claim 13, comprising one or more metal oxide selected from the group consisting of CuO, V2O5 and WO3.

18. An electronic part comprising said dielectric composition of claim 13.

19. The electronic part of claim 18 being a laminate type dielectric filter

20. A dielectric composition for firing at low temperatures comprising a main composition of x.BaO-y.TiO2-z1.Nd2O3-z2.La2O3 —z3.Sm2O3-t.Bi2O3 (x+y+z1+z2+z3+t=1; 0.100≦x≦0.250; 0.600≦y≦0.750; 0.010≦z1≦0.120; 0.000≦z2≦0.120; 0.000≦z3≦0.120; 0.010≦(z1+z2+z3)≦0.120; 0.065≦—t≦0.075; 0.35≦t/(z1+z2+z3+t) and B2O3 in an amount of 0.05 to 10 weight parts with respect to 100 weight parts of said main composition.

21. The dielectric composition of claim 20, comprising one or more metal element selected from the group consisting of Ag, Cu and Ni in a total amount of 5 weight percent or lower.

22. The dielectric composition of claim 20, comprising one or more metal oxide selected from the group consisting of CuO, V2O5 and WO3.

23. An electronic part comprising said dielectric composition of claim 20.

24. The electronic part of claim 23 being a laminate type dielectric filter.