Patent Grant
8070984
1. Field of Invention
Embodiments of the present invention relate generally to fluorescent materials containing rare earth elements and, more particularly, to such luminescent materials for exciting ultraviolet as well as visible light containing lead- and/or copper-containing compounds.
2. Description of the Related Art
Lead and copper activated materials are known for short wave excitation, e.g. from a low pressure mercury lamp, such as barium disilicate activated by lead (Keith H. Butler, The Pennsylvania State University Press, 1980, S 175, orthosilicate activated by lead (Keith H. Butler, The Pennsylvania State University Press, 1980, S. 181), akermanites activated by lead, or Ca-metasilicate activated by Pb2+.
Generally, the maxima of the emission bands of such lead activated phosphors are located between 290 nm and 370 nm at 254 nm excitation. Bariumdisilicate activated by lead is an U.V. emitting phosphor which currently is used in sun parlor lamps.
Lead has in the ground state 1S0 two outer electrons. The electron configuration of the ground state is d10s2, so that the lowest excited state has d10sp configuration. The excited sp configuration has four levels, 3P0, 3P1, 3P2 and 1P1, which can be achieved between 165.57 nm (3P0) and 104.88 nm (1P1) in the free ion. Transitions between 1S0 and 1P1 excited level are allowed by all selection rules. While transitions between 1S0 and 3P0 are only allowed with the lowest symmetry, transitions between 1S0 and 3P1 as well as 3P2 are allowed only under certain conditions. However, excitation between 180 and 370 nm has the same emission. Excitation with wavelength longer than 370 nm is not possible.
Otherwise, luminescent materials are known having lead as a host lattice component. Molybdate phosphors containing MoO42−-centers are described in Bernhardt, H. J., Phys. Stat. Sol. (a), 91,643, 1985. PbMoO4 shows at room temperature red emission with an emission maximum at 620 nm under photoexcitation at 360 nm.
However, such emission is not caused by lead itself. In molybdates the luminescence properties are not caused by the metal ion M2+ (M2+MoO4 where M2+=Ca, Sr, Cd, Zn, Ba, Pb etc). Here, defect centers of MoO42− ions coupled to O2−-ion vacancies seem to be the reason. Nevertheless, the Pb2+-ion influences the preferred emission properties because it stabilizes the host lattice.
As a familiar example, tungstates (Ca,Pb)WO4 as mixed crystals have a strong green emission with high quantum output of 75% (Blasse, G., Radiationless processes in luminescent materials, in Radiationless Processes, DiBartolo, B., Ed. Plenum Press, New York, 1980, 287). Under 250 nm excitation PbWO4 shows blue emission and under 313 nm excitation PbWO4 has an orange emission band, which can be caused by Schottky defects or by impurity ions (Phosphor Handbook, edited under the Auspice of Phosphor Research Society, CRC Press New York, 1998, S 205).
Copper was used as a monovalent activator in orthophosphates (Wanmaker, W. L. and Bakker, C., J. Electrochem. Soc., 106, 1027, 1959) with an emission maximum at 490 nm. The ground state of monovalent copper is a filled shell 3d10. That is the level 1S0. After exciting the lowest excited configuration is 3d94s. This configuration has two terms, 3D and 1D. The next higher configuration, 3d94p, gives 6 terms 3Po, 3Fo, 3Do, 1Fo, 1Do and 1Po. The transitions between the ground state 1S0 and the 1D or 3D are forbidden by parity or spin, respectively. In copper ions, the excitation to the crystal field levels of 4p terms is allowed. Emission will be got either by a direct return from the crystal field odd state to the ground state or by a combination of transitions first from the odd state to a crystal field level and after that a second transition from these 3D or 1D state of the 3d94s configuration to the ground state.
The ground state of bivalent copper has 3d9-configuration. That is the level 2D5/2. In the bivalent copper, one of the d-electrons can be excited to the 4s or 4p orbital. The lowest exciting configuration is the 3d84s with two quartet terms 4F, 4P and four doublet terms, 2F, 2D, 2P and 2G without emission caused by forbidden transitions. The higher exciting configuration is the 3d84p-configuration with four terms 4Do, 4Go, 4Fo, and 4Po, where emission can occur.
Copper activated or co-activated sulphide-phosphors are well known and they are commercial used for cathode ray tubes. The green-emitting ZnS:Cu, Al (wherein, the copper is used as activator and Al is used as co-activator) is very important in CRT applications.
In zinc-sulphide phosphors, the luminescent materials can be classified into five kinds, depending on the relative ratio of the concentration of activators and co-activators (van Gool, W., Philips Res. Rept. Suppl., 3, 1, 1961). Here, the luminescent centers are formed from deep donors or deep acceptors, or by their association at the nearest-neighbor sites (Phosphor Handbook, edited under the Auspice of Phosphor Research Society, CRC Press New York, 1998, S. 238).
Orthophosphates activated by copper (Wanmaker, W. L., and Spier, H. L., JECS 109 (1962), 109), and pyrophosphates, alumosilicates, silicates, and tripolyphosphates all activated by copper are described in “Keith H. Butler, The Pennsylvania State University Press, 1980, S. 281”. However, such phosphors can only be used for a short wave U.V. excitation. Because of their unstable chemical properties and their temperature behavior, they cannot be used in fluorescent lamps.
It has been observed that conventional luminescent materials are generally unstable in water, air humidity, water steam and polar solvents.
One embodiment exemplarily described herein can be generally characterized as a luminescent material for a light emitting diode (LED) that includes a first compound including a host lattice and a luminescent ion within the host lattice. The host lattice may include first ions and oxygen. A first portion of the first ions may be substituted by divalent copper ions. The first compound may emit light upon excitation with ultraviolet light or visible light emitted by the LED. The first compound may have an Olivine crystal structure, a β-K2SO4 crystal structure, a trigonal Glaserite (K3Na(SO4)2) or monoclinic Merwinite crystal structure, a tetragonal Ackermanite crystal structure, a tetragonal crystal structure or an orthorhombic crystal structure. According to another embodiment, the luminescent ion includes at least one of Bi, Sn, Sb, Sc, Y, La, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. According to another embodiment, the first compound includes Ge. According to another embodiment, the luminescent material further includes at least one second compound selected from the group consisting of an aluminate, a silicate, an antimonate, a germanate, a germanate-silicate and a phosphate. According to another embodiment, the luminescent material emits white light upon excitation with ultraviolet light or visible light.
Another embodiment exemplarily described herein can be generally characterized as a luminescent material for a light emitting diode (LED) that includes a first compound including a host lattice and a luminescent ion within the host lattice. The host lattice may include first ions and oxygen. A first portion of the first ions may be substituted by copper ions. The first compound may emit light upon excitation with ultraviolet light or visible light emitted by the LED. However, the copper ions do not act as luminescent ions upon excitation with the ultraviolet light or visible light.
According to embodiments exemplarily described herein, a luminescent material may include one or more lead- and/or copper-containing chemical compounds. The luminescent material may be excited by UV and/or visible (e.g., blue) light. In some embodiments, the lead- and/or copper-containing chemical compounds may be generally characterized as including a host lattice having anions and cations. In some embodiments, at least a portion of the cations are divalent cations. In some embodiments, the divalent cations include alkaline earth ions. In some embodiments, at least a portion of the divalent cations of the host lattice are substituted by divalent lead and/or divalent copper ions.
As mentioned above, conventional luminescent materials are generally unstable in water, air humidity, water steam and polar solvents. However, due to a higher covalency and a lower basicity, the substitutionally-incorporated divalent lead and/or divalent copper ions in the host lattice of the chemical compound yields luminescent materials having improved resistance against water, air humidity and polar solvents.
The divalent lead and/or divalent copper ions within the host lattice do not act as activators (also referred to herein as “luminescent ions”) and, therefore do not luminance. Rather, it has been found that these ions tend to influence the crystal field splitting as well as the covalency of the chemical compound. As a result, the substitutional incorporation of divalent lead and/or copper ions within the host lattice tends to influence luminescent-optical properties of the chemical compounds so as to improve luminescent intensity and desirably shift the emission maxima, color points, and shape of emission spectra.
It has been found that phosphors having chemical compounds that contain substitutionally-incorporated divalent lead and/or divalent copper ions show improved emission intensities as compared with phosphors having chemical compounds that do not contain substitutionally-incorporated divalent lead and/or divalent copper ions.
In addition, it has been found that phosphors having chemical compounds that contain substitutionally-incorporated divalent lead and/or divalent copper ions tend to show improved luminescent properties for excitation wavelength higher than about 360 nm. At excitation wavelengths higher than about 360 nm, the divalent lead and/or divalent copper ions do not exhibit their own radiation transfers due to the energy levels of their electron configuration, so that any kind of exciting radiation cannot be lost. Furthermore, by substitutionally incorporating divalent lead and/or divalent copper ions, the emission wavelength can be shifted to higher or lower energies as desired.
Lead ions having an ionic radius of 119 pm can substitute the alkaline earth ions Ca having an ionic radius of 100 pm and Sr having an ionic radius of 118 pm very easily. The electro negativity of lead with 1.55 is much higher than that of Ca (1.04) and Sr (0.99). The preparation of substances containing lead is complicated due to the possibility of an oxidation of these ions in reducing atmospheres. For the preparation of lead-containing compounds, which need reducing atmosphere, special preparation processes are necessary.
The influence of substitutionally-incorporated divalent lead ions in the crystal field on the shifting of emission characteristics depends upon the substituted ions. When divalent lead ions substitute Sr or Ba in Eu-activated aluminates and/or silicates, the emission maximum tends to be shifted to longer wavelengths due to smaller ionic radii of Pb as compared with the ionic radii of Ba and Sr. That leads to a stronger crystal field surrounding the activator ion.
A similar effect shows the substitution of divalent copper ions for alkaline earth ions. Here, an additional influence is effective. Due to the higher ionic potential of copper as a quotient of ionic charge and ionic radius compared to the bigger alkaline earth ions, the copper ions can attract the neighboring oxygen ions stronger than the alkaline earth ions. So the substitution of the bigger alkaline earth ions Ca, Sr and Ba by copper leads to a stronger crystal field in the surrounding of the activator ions, too. Thus, the shape of emission bands can be influenced, the shifting of the emission peak to longer wavelength is connected in a broadening of the emission curves for band emission. In addition, it should be possible to increase the intensity of emission by substitution of ions copper and lead. Generally, the shifting of emission peaks to longer or shorter wavelengths are desirable in the field of LED lighting. Here, it is necessary to realize a fine tuning to get a special wavelength for desired color points as well as for better brightness of optical devices. By using cations, copper and lead, such a fine tuning should be possible.
As described above, the luminescent material may include one or more chemical compounds such as, for example, aluminates, silicates, antimonates, germinates, germinate-silicates, and/or phosphates. Exemplary embodiments of these luminescent materials are described in greater detail below.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing aluminates exemplarily characterized according to the formula as follows:
a(M′O).b(M″2O).c(M″X).d(Al2O3).e(M′″O).f(M″″2O3).g(M′″″oOp).h(M″″″xOy) (1)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be one or more monovalent elements, for example, Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be one or more divalent elements, for example, Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be one or more trivalent elements, for example, Sc, B, Ga, In, and/or any combination thereof; M′″″ may be Si, Ge, Ti, Zr, Mn, V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦2; 0<d≦8; 0<e≦4; 0≦f≦3; 0≦g≦8; 0<h≦2; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5.
a(M′O).b(M″2O).c(M″X).4-a-b-c(M′″O).7(Al2O3).d(B2O3).e(Ga2O3).f(SiO2).g(GeO2).h(M″″xOy) (2)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be one or more monovalent elements, for example, Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof, M′″ may be one or more divalent elements, for example, Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Bi, Sn, Sb, Sc, Y, La, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and any combination thereof, X may be F, Cl, Br, I, and any combination thereof; 0<a≦4; 0≦b≦2; 0≦c≦2; 0≦d≦1; 0≦e≦1; 0≦f≦1; 0≦g≦1; 0<h≦1; 1≦x≦2; and 1≦y≦5.
The preparation of copper- as well as lead-containing luminescent materials may be a basic solid state reaction. Pure starting materials without any impurities, e.g. iron, may be used. Any starting material which may transfer into oxides via a heating process may be used to form oxygen dominated phosphors.
Preparation of the Luminescent Material Having Formula (3)
Cu0.02Sr3.98Al14O25:Eu (3)
Starting materials: CuO, SrCO3, Al(OH)3, Eu2O3, and/or any combination thereof.
The starting materials in the form of oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, e.g., H3BO3. The mixture may be fired in an alumina crucible in a first step at about 1,200° C. for about one hour. After milling the pre-fired materials a second firing step at about 1,450° C. in a reduced atmosphere for about 4 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 494 nm.
Preparation of the Luminescent Material Having Formula (4)
Pb0.05Sr3.95Al14O25:Eu (4)
Starting materials: PbO, SrCO3, Al2O3, EU2O3, and/or any combination thereof.
The starting materials in form of very pure oxides, carbonates, or other components which may decompose thermally into oxides, may be mixed in stoichiometric proportion together with small amounts of flux, for example, H3BO3. The mixture may be fired in an alumina crucible at about 1,200° C. for about one hour in the air. After milling the pre-fired materials a second firing step at about 1,450° C. in air for about 2 hours and in a reduced atmosphere for about 2 hours may be followed. Then the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum of from about 494.5 nm.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing aluminates exemplarily characterized according to the formula as follows:
a(M′O).b(M″O).c(Al2O3).d(M′″2O3).e(M″″O2).f(M′″″xOy) (5)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M′″ may be B, Ga, In, and/or any combination thereof; M′″″ may be Si, Ge, Ti, Zr, Hf, and/or any combination thereof; M′″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; 0<a≦1; 0≦b≦2; 0<c≦8; 0≦d≦1; 0≦e≦1; 0<f≦; 1≦x≦2; and 1≦y≦5.
The luminous peak and density of Example 2 are described in Table 7, which will be shown below.
Preparation of the Luminescent Material Having Formula (6)
Cu0.05Sr0.95Al1.9997Si0.0003O4:Eu (6)
Starting materials: CuO, SrCO3, Al2O3, SiO2, Eu2O3, and/or any combination thereof.
The starting materials in the form of, for example, pure oxides and/or as carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, AlF3. The mixture may be fired in an alumina crucible at about 1,250° C. in a reduced atmosphere for about 3 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 521.5 nm.
Preparation of the Luminescent Material Having Formula (7)
Cu0.12BaMg1.88Al16O27:Eu (7)
Starting materials: CuO, MgO, BaCO3, Al(OH)3, Eu2O3, and/or any combination thereof.
The starting materials in the form of, for example, pure oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, AlF3. The mixture may be fired in an alumina crucible at about 1,420° C. in a reduced atmosphere for about 2 hours. After that the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum of about 452 nm.
Preparation of the Luminescent Material Having Formula (8)
Pb0.1Sr0.9Al2O4:Eu (8)
Starting materials: PbO, SrCO3, Al(OH)3, Eu2O3, and/or any combination thereof.
The starting materials in form of, for example, pure oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, H3BO3. The mixture may be fired in an alumina crucible at about 1,000° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at about 1,420° C. in the air for about 1 hour and in a reduced atmosphere for about 2 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 521 nm.
Results obtained in regard to copper- and/or lead-containing aluminates are shown in table 7.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing silicates exemplarily characterized according to the formula as follows:
a(M′O).b(M″O).c(M′″X).d(M′″2O).e(M″″2O3).f(M′″″oOp).g(SiO2).h(M″″″xOy) (9)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M″″ may be Al, Ga, In, and/or any combination thereof; M′″″ may be Ge, V, Nb, Ta, W, Mo, Ti, Zr, Hf, and/or any combination thereof; M″″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; X may be F, Cl, Br, I, and any combination thereof; 0<a≦2; 0<b≦8; 0≦c≦4; 0≦d≦2; 0≦e≦2; 0≦f≦2; 0<g≦10; 0<h≦5; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5.
The copper-containing silicates exemplarily described herein may, in some embodiments, contain SiO4 and be characterized as having an Olivine structure (orthorhombic) or β-K2SO4 structure (orthorhombic); contain Si2O8 and be characterized as having a trigonal Glaserite (K3Na(SO4)2) or monoclinic Merwinite structure; contain Si2O7 and be characterized as having a tetragonal Ackermanite structure; contain SiO5 and be characterized as having a tetragonal structure; and/or contain Si2O5 and be characterized as having an orthorhombic structure.
The superior luminous density of Example 3 can be seen below.
Preparation of the Luminescent Material Having Formula (10)
Cu0.05Sr1.7Ca0.25SiO4:Eu (10)
Starting materials: CuO, SrCO3, CaCO3, SiO2, Eu2O3, and/or any combination thereof.
The starting materials in the form of pure oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. The mixture may be fired in an alumina crucible at about 1,200° C. in an inert gas atmosphere (e.g., N2 or noble gas) for about 2 hours. Then the material may be milled. After that, the material may be fired in an alumina crucible at about 1,200° C. in a slightly reduced atmosphere for about 2 hours. Then, the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum at about 592 nm.
Preparation of the Luminescent Material Having Formula (11):
Cu0.2Ba2Zn0.2Mg0.6Si2O7:Eu (11)
Starting materials: CuO, BaCO3, ZnO, MgO, SiO2, EU2O3, and/or any combination thereof.
The starting materials in the form of very pure oxides and carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. In a first step the mixture may be fired in an alumina crucible at about 1,100° C. in a reduced atmosphere for about 2 hours. Then the material may be milled. After that the material may be fired in an alumina crucible at about 1,235° C. in a reduced atmosphere for about 2 hours. Then that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 467 nm.
Preparation of the Luminescent Material Having Formula (12)
Pb0.1Ba0.95Sr0.95Si0.998Ge0.002O4:Eu (12)
Starting materials: PbO, SrCO3, BaCO3, SiO2, GeO2, Eu2O3, and/or any combination thereof.
The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. The mixture may be fired in an alumina crucible at about 1,000° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at 1,220° C. in air for 4 hours and in reducing atmosphere for 2 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 527 nm.
Preparation of the Luminescent Material Having Formula (13)
Pb0.25Sr3.75Si3O8Cl4:Eu (13)
Starting materials: PbO, SrCO3, SrCl2, SiO2, Eu2O3, and any combination thereof.
The starting materials in the form of oxides, chlorides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. The mixture may be fired in an alumina crucible in a first step at about 1,100° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at about 1,220° C. in the air for about 4 hours and in a reduced atmosphere for about 1 hour may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 492 nm.
Results obtained with respect to copper- and/or lead-containing silicates are shown in table 12.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing antimonates exemplarily characterized according to the formula as follows:
a(M′O).b(M″2O).c(M″X).d(Sb2O5).e(M′″O).f(M″″xOy) (14)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Bi, Sn, Sc, Y, La, Pr, Sm, Eu, Tb, Dy, Gd, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦4; 0<d≦8; 0≦e≦8; 0≦f≦2; 1≦x≦2; and 1≦y≦5.
Preparation of the Luminescent Material Having Formula (15)
Cu0.2Mg1.7Li0.2Sb2O7:Mn (15)
Starting materials: CuO, MgO, Li2O, Sb2O5, MnCO3, and/or any combination thereof.
The starting materials in the form of oxides may be mixed in stoichiometric proportion together with small amounts of flux. In a first step the mixture may be fired in an alumina crucible at about 985° C. in the air for about 2 hours. After pre-firing the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,200° C. in an atmosphere containing oxygen for about 8 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 626 nm.
Preparation of the Luminescent Material Having Formula (16)
Pb0.006Ca0.6Sr0.394Sb2O6 (16)
Starting materials: PbO, CaCO3, SrCO3, Sb2O5, and/or any combination thereof.
The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux. In a first step the mixture may be fired in an alumina crucible at about 975° C. in the air for about 2 hours. After pre-firing the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,175° C. in the air for about 4 hours and then in an oxygen-containing atmosphere for about 4 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 637 nm.
Results obtained in respect to copper- and/or lead-containing antimonates are shown in table 15.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing germinates and/or a germinate-silicates exemplarily characterized according to the formula as follows:
a(M′O).b(M″2O).c(M″X).d(GeO2).e(M′″O).f(M″″2O3).g(M′″″oOp).h(M″″″xOy) (17)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, and/or any combination thereof; M″″ may be Sc, Y, B, Al, La, Ga, In, and/or any combination thereof; M′″″ may be Si, Ti, Zr, Mn, V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Pr, Sm, Eu, Gd, Dy, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦10; 0<d≦10; 0≦e≦14; 0≦f≦14; 0≦g≦10; 0≦h≦2; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5.
Preparation of the Luminescent Material Having Formula (18)
Pb0.004Ca1.99Zn0.006Ge0.8Si0.2O4:Mn (18)
Starting materials: PbO, CaCO3, ZnO, GeO2, SiO2, MnCO3, and/or any combination thereof,
The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. In a first step the mixture may be fired in an alumina crucible at about 1,200° C. in an oxygen-containing atmosphere for about 2 hours. Then, the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,200° C. in oxygen containing atmosphere for about 2 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 655 nm.
Preparation of the Luminescent Material Having Formula (19)
Cu0.46Sr0.54Ge0.6Si0.4O3:Mn (19)
Starting materials: CuO, SrCO3, GeO2, SiO2, MnCO3, and/or any combination thereof.
The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH4Cl. In a first step the mixture may be fired in an alumina crucible at about 1,100° C. in an oxygen-containing atmosphere for about 2 hours. Then, the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,180° C. in an oxygen-containing atmosphere for about 4 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 658 nm.
Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing phosphates exemplarily characterized according to the formula as follows:
a(M′O).b(M″2O).c(M″X).d(P2O5).e(M′″O).f(M″″2O3).g(M′″″O2).h(M″″″xOy) (20)
wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Sc, Y, B, Al, La, Ga, In, and/or any combination thereof; M′″″ may be Si, Ge, Ti, Zr, Hf, V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Pr, Sm, Eu, Gd, Dy, Ce, Tb, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦12; 0≦c≦16; 0≦d≦3; 0≦e≦5; 0≦f≦3; 0≦g≦2; 0<h≦2; 1≦x≦2; and 1≦y≦5.
The luminescent materials comprising the lead- and/or copper-containing phosphates may be used as compounds for ultraviolet light in a light emitting device.
Preparation of the Luminescent Material Having Formula (21)
Cu0.02Ca4.98(PO4)3Cl:Eu (21)
Starting materials: CuO, CaCO3, Ca3(PO4)2, CaCl2, Eu2O3, and/or any combination thereof,
The starting materials in the form of oxides, phosphates, and/or carbonates and chlorides may be mixed in stoichiometric proportions together with small amounts of flux. The mixture may be fired in an alumina crucible at about 1,240° C. in reducing atmosphere for about 2 hours. After that the material may be milled, washed, dried and sieved. The luminescent material may have an emission maximum at about 450 nm.
The lead- and/or copper-containing luminescent materials exemplarily described above can act as converter for light emitting devices, such as ultraviolet as well as blue emitting LEDs, back lights and painting pigments. They can convert the excitation wavelength from the ultraviolet and blue light to longer visible wavelength. According to some embodiments, one or more of the lead- and/or copper-containing luminescent materials exemplarily described above may be used or mixed to produce a luminescent material with a color temperature ranging from about 2,000K to about 8,000K or about 10,000K and superior color rendering index of greater than about 60 (e.g., between about 60 and about 90, or greater than about 90, or between about 90 and about 95). Thus, for all color temperatures as well as for all color coordinates inside of the white light coordinates, an appropriate luminescent material or mixture thereof can be found.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-042397 | Jun 2004 | KR | national |
This application is a continuation-in-part of U.S. patent application Ser. No. 11/024,722, filed on Dec. 30, 2004, the disclosure of which is incorporated by reference herein in its entirety, which claims priority to Korean Patent Application No. 2004-042397, filed Jun. 10, 2004, the disclosure of which is incorporated by reference herein in its entirety.
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