Highly saturated red-emitting Mn (IV) activated phosphors and method of fabricating the same

Abstract

The present invention provides a light emitting device comprising a semiconductor light source emitting radiation at about 250˜500 nm; and a phosphor composition radiationally coupled to the semiconductor light source, wherein the phosphor composition is selected from the group consisting of Mg14(Ge(5-a)Mna)O24, Sr(Ge(4-b)Mnb)O9, Mg2(Ti(1-c)Mnc)O4, Zn2(Ti(1-d)Mnd)O4, SrMg(Al(10-e)Mne)O17, and Y3(Ga(5-f)Mnf)O12.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows comparison of XRD profiles from Mg₁₄Ge₅O₂₄ phosphor compositions synthesized at various sintering temperatures.

FIG. 2 shows comparison of XRD profiles from a series of Mg₁₄Ge₅O₂₄ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 3 shows excitation and photoluminescence spectra of Mg₁₄Ge₅O₂₄ phosphor composition synthesized at 1200° C.

FIG. 4 shows concentration effect of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition.

FIG. 5 shows chromaticity coordinates of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition.

FIG. 6 shows comparison of XRD profiles from SrGe₄O₉:xMn⁴⁺ phosphor compositions synthesized at various sintering temperatures.

FIG. 7A shows comparison of XRD profiles from a series of SrGe₄O₉:xMn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 7B shows comparison of XRD profiles from a series of SrGe₄O₉:xMn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 8 shows excitation and photoluminescence spectra of SrGe₄O₉:xMn⁴⁺ phosphor composition synthesized at 1100° C.

FIG. 9 shows concentration effect of SrGe₄O₉:xMn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺.

FIG. 10 shows C.I.E. chromaticity coordinates of SrGe₄O₉:Mn⁴⁺ phosphor composition.

FIG. 11 shows comparison of XRD profiles from Mg₂TiO₄:Mn⁴⁺ phosphor compositions synthesized at various temperatures.

FIG. 12A shows comparison of XRD profiles from a series of Mg₂TiO₄:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 12B shows comparison of XRD profiles from a series of Mg₂TiO₄:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 13 shows excitation and photoluminescence spectra of Mg₂TiO₄:Mn⁴⁺ phosphor synthesized at 1300° C.

FIG. 14 shows concentration effect of Mg₂TiO₄:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺.

FIG. 15 shows C.I.E. chromaticity coordinates of Mg₂TiO₄:Mn⁴⁺ phosphor composition.

FIG. 16 shows comparison of XRD profiles from Zn₂TiO₄:Mn⁴⁺ phosphor compositions synthesized at various temperatures.

FIG. 17A shows comparison of XRD spectra from a series of Zn₂TiO₄:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 17B shows comparison of XRD profiles from a series of Zn₂TiO₄:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 18 shows excitation and photoluminescence spectra of Zn₂TiO₄:Mn⁴⁺ phosphor composition synthesized at 1300° C.

FIG. 19 shows concentration effect of Zn₂TiO₄:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺.

FIG. 20 shows C.I.E. chromaticity coordinates of Zn₂TiO₄:Mn⁴⁺ phosphor composition.

FIG. 21 shows comparison of XRD profiles from SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor compositions synthesized at various sintering temperatures.

FIG. 22A shows comparison of XRD spectra from a series of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 22B shows comparison of XRD profiles from a series of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 23 shows excitation and photoluminescence spectra of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition.

FIG. 24 shows concentration effect of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺.

FIG. 25 shows C.I.E. chromaticity coordinates of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition.

FIG. 26 shows comparison of XRD profiles from Y₃Ga₅O₁₂:Mn⁴⁺ phosphor compositions synthesized at various temperatures.

FIG. 27A shows comparison of XRD profiles from a series of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 27B shows comparison of XRD profiles from a series of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition samples doped with various concentrations of Mn⁴⁺.

FIG. 28 shows excitation and photoluminescence spectra of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition.

FIG. 29 shows concentration effect of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺.

FIG. 30 shows C.I.E. chromaticity coordinates of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition.

DETAILED DESCRIPTION OF THE INVENTION

For a better understanding of the composition of components and mechanical properties, in addition, objects, technical description, features, and effects of the present invention by those familiar in this field, the present invention is described with reference to the following embodiments, figures and tables.

The present invention relates to a light emitting device using novel highly saturated red phosphor compositions excitable by UV.

Phosphor convertible materials (phosphor convertible compositions) is capable of transferring received UV or blue light into visible light with different wavelength that is determined by specific component in the phosphor composition. A phosphor composition is composed of single or two or more compositions. It is necessary for LED usable as light source to generate sufficiently bright and white light. In one embodiment of the present invention, a phosphor composition is coated on LED in order to generate white light. Phosphor composition emits lights of different colors when excited by lights with different wavelengths. For example, near ultraviolet or blue light LED emits visible light when excited with wavelength at 250˜500 nm. Emitting visible light converted by phosphor composition is characterized to exhibit high intensity and brightness.

One of the preferred embodiments of the present invention is a light emitting device or lamp comprising a semiconductor light source, i.e., light emitting diode chip, and conductive leads connected to the chip. The conductive leads are supported by electrode sheets to provide electricity to the chip and enable radiation emitting.

Also, light emitting device can comprise blue or UV semiconductor light source, radiation generated by which is emitted on phosphor composition directly to generate white light. In a preferred embodiment of the present invention, various impurities are doped into the blue light emitting device. Therefore, the LED comprises a variety of suitable III-V, II-VI or IV-IV semiconductor (e.g., GaN, ZnSe or SiC) layers, and wavelength of emitted radiation is preferably 250˜500 nm. For example, LED consisting of nitride In_iGa_jAl_kN (wherein 0≦1,0≦j, and 0≦k; i+j+k=1) is capable of exciting light with wavelength longer than 250 nm and shorter than 500 nm. Above-mentioned LED is conventionally known and can be used as exciting light source in the present invention. However, the present invention is not limited thereto, and all kinds of light sources excitable by semiconductor, including semiconductor laser light source, are useful.

Further, while discussed LED is referred to inorganic LED, it is apparent for those in this field to appreciate that it is replaceable with organic LED or any other radiation source.

The present invention provides a light emitting device comprising a semiconductor light source that emits light with wavelength at 250˜500 nm; and a phosphor composition excitable by said light source, selected from the group consisting of Mg₁₄Ge_(5-a)O₂₄:aMn⁴⁺, SrGe_(4-b)O₉:bMn⁴⁺, Mg₂Ti_(1-c)O₄:cMn⁴⁺ Zn₂Ti_(1-d)O₄:dMn⁴⁺, SrMgAl_(10-e)o₁₇:eMn⁴⁺, and Y₃Ga_(5-f)o₁₂:fMn⁴⁺. Said semiconductor light source can be LED as well as organic LED. The present phosphor composition is coated on said LED used as light source to generate white light.

Based on that main body most suitable for Mn⁴⁺ is six-coordinate and quantum efficiency of phosphor is elevated by Mn⁴⁺, the present invention is achieved by preparing the phosphor composition according to:

• • 1. Mn⁴⁺ enters host lattice sites with similar radius;
  • 2. Substitution site of the main body suitable for Mn⁴⁺ is six-coordinated;
  • 3. Excitation and emission of Mn⁴⁺ are explainable by Tanabe-Sugano diagram for d³ free ion, so that crystal field strength parameter (Dq) and Racah parameter (B) are estimated.
  • 4. Cation with smaller atomic mass is used to form main body for Mn⁴⁺ phosphor composition to improve quantum efficiency.

Following is the description for embodiments of the present invention, compositions 1-7. Instruments used in the present invention are: high temperature oven set, high temperature ventilation tubular oven, X-ray diffractometer (Bruker AXS D8), spectrofluorometer (Spex Fluorog-3; Jobin Yvon-Spex Instruments), color analyzer (DT-100 color analyzer; LAIKO), and UV-VIS spectrometer (U-3010; Hitachi), etc.

Preparation of Phosphor Composition

(1) Preparation of Mg₁₄Ge₅O₂₄:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.15˜2.5%) weighed MgO, GeO₂ and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1000˜1300° C. for 8 hours. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to sintered pale yellow powders.

(2) Preparation of SrGe₄O₉:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.15˜2.5%) weighed SrCO₃, GeO₂ and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1000˜1100° C. for 8 hours. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to sintered pink powders.

(3) Preparation of Mg₂TiO₄:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.05˜2%) weighed MgO, TiO₂ and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1300˜1500° C. for 8 hours. Sintered powders were annealed by sintering at 570° C. for 16 hours in oven with flowing oxygen. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to the resultant orange powders.

(4) Preparation of Zn₂TiO₄:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.05˜2%) weighed ZnO, TiO₂ and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1200˜1400° C. for 8 hours. Sintered powders were annealed by sintering at 570° C. for 16 hours in oven with flowing oxygen. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to the resultant orange powders.

(5) Preparation of SrMgAl₁₀O₁₇:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.05˜1.5%) weighed SrCO₃, MgO, Al₂O₃, and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1300˜1600° C. for 8 hours. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to sintered orange powders.

(6) Preparation of Y₃Ga₅O₁₂:xMn⁴⁺ Phosphor Composition:

Stoichiometrically (x=0.05˜1.5%) weighed Y₂O₃, Ga₂O₃ and MnO₂ were uniformly mixed and milled for 30 minutes, then were put into aluminum oxide crucible to sinter at 1000˜1400° C. for 8 hours. Related physical optic measurements, including analysis of X-ray diffraction on crystalline phase and structure, photoluminescence spectrum, C.I.E. chromaticity coordinate, etc., were conducted to sintered pink powders.

Physical Optic Measurements of Phosphor Composition

Composition 1

(Physical Property of Mg₁₄Ge₅O₂₄:Mn⁴⁺ Phosphor Composition)

Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition was prepared by solid state synthesis. Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition of single phase with good crystallinity was obtained at synthesis temperature of 1200° C., while at synthesis temperature of 1100° C., starting materials MgO and GeO₂ were remained in sintered product and crystalline was not good. Also, at synthesis temperature of 1300° C., slight fusion occurred and reactants were vaporized. FIG. 1 shows Mg₁₄Ge₅O₂₄:Mn⁴⁺ prepared at various sintering temperatures, in which crystallization phase obtained at 1200° C. was confirmed by comparison to be pure. FIG. 2 shows XRD spectra from a series of samples doped with various concentration of Mn⁴⁺. It can be seen that X-ray diffraction spectra are similar at low dope concentrations; when dopant concentration is above 0.5 mol %, growth rate of crystallization phase with Miller index (520) is decreased, and growth of crystallization phase with (422) is preferred.

(Optical Property of Mg₁₄Ge₅O₂₄:Mn⁴⁺ Phosphor Composition)

FIG. 3 shows the photoluminescence spectra of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition synthesized at 1200° C. In FIG. 3, dashed line represents excitation spectrum, wherein excitation wavelength at 327 and 419 nm are preferred, and that at 419 nm is more preferred. Solid line represents emission spectrum consisting of 6 narrow peaks, wherein emission intensity of peak at 659 nm in red area is highest, and both excitation and emission wavelengths are not affected by doped amount of Mn⁴⁺. Therefore, in the process of excitation to emission, Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition is excited as ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂, and emits as ²E→⁴A₂, wherein the lowest excited state of energy levels in crystalline field is ²E, and ground state is ⁴A₂. Generally, phosphor composition is excited to ⁴T₁ and ⁴T₂, and then relaxes to ²E to produce ²E→⁴A₂ emission.

FIG. 4 shows the concentration effect of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺. As can be seen, intensity of luminescence increases as doped amount of Mn⁴⁺ is increased, and is highest at 0.25 mol %. While doped amount of Mn⁴⁺ is above 0.5 mol %, concentration quenching occurs due to Mn⁴⁺ concentration is too high, so that emitting intensity decreases. Variation of integrated area of emission spectrum according to Mn⁴⁺ concentration is identical with that of intensity of emission spectrum.

FIG. 5 shows the C.I.E. chromaticity coordinate of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor composition. As can be seen, a series of Mg₁₄Ge₅O₂₄ samples are excited with 419 nm, wherein chromaticity coordinate value of sample doped with 0.05˜0.5 mol % of Mn⁴⁺, represented by ‘*’, is (0.71, 0.27), and that doped with 1 mol %, represented by ‘Δ’, is (0.72, 0.27); both are much better than current commercial product Y₂O₂S:Eu³⁺ (0.64, 0.35). However, chromaticity coordinate shifts to right as emission intensity decreases, and shows extensive red emission when seen by naked eye. According to photoluminescence wavelength of 652 nm, it is reasonable to obtain such high color saturation. Table 1 shows comparison of chromaticity coordinate values of Mg₁₄Ge₅O₂₄:Mn⁴⁺ phosphor compositions doped with various concentration of Mn⁴⁺.

TABLE 1
Mn4+ mol %	x ordinate value	y ordinate value
0.05	0.72	0.27
0.15	0.72	0.27
0.25	0.72	0.27
0.5	0.72	0.27
1.0	0.71	0.27

Composition 2

(Physical Property of SrGe₄O₉:Mn⁴⁺ Phosphor Composition)

SrGe₄O₉:xMn⁴⁺ phosphor composition was prepared by solid state synthesis. No single phase appeared at initial sintering temperature of 900° C., and parent SrGe₄O₉ was found at 1000° C. but crystallinity was not good. Fused state product was found at 1200° C. FIG. 6 shows samples synthesized at various sintering temperatures. As can been, until temperature was elevated up to 1100° C., SrGe₄O₉:xMn⁴⁺ phosphor composition of single phase with good crystallinity was obtained

FIGS. 7A and 7B show the XRD profiles from a series of SrGe₄O₉:Mn⁴⁺ samples doped with various concentration of Mn⁴⁺. Structure of SrGe₄O₉ was not affected by Mn⁴⁺ in dopant concentration ranging from 0.15 to 2.5 mol %.

(Optical Property of SrGe₄O₉:Mn⁴⁺ Phosphor Composition)

FIG. 8 shows the photoluminescence spectra of SrGe₄O₉:Mn⁴⁺ phosphor composition synthesized at 1200° C. Dashed line at left hand represents excitation spectrum, wherein excitation wavelength at 329 nm originating from transfer band of O₂₋P→Mn⁴⁺3d is preferred. Small peak at 312 nm approximating to said band may originate from ⁴A₂→⁴T₁, and those at 325 and 419 nm originate from ⁴A₂→²T and ⁴A₂⁴T₂, respectively. Since ⁴A₂→²T₁ is spin-forbidden, it shows weaker intensity compared to ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂. Solid line represents linear peaks appearing in 620˜700 nm, similar to those from SrGe₄O₉:Mn⁴⁺, in which emission peak at 655 nm originates from ²E→⁴A₂.

FIG. 9 shows the concentration effect of SrGe₄O₉:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺. As can be seen, intensity of luminescence is highest at dopant concentration of 1 mol %. While dopant concentration is above 1 mol %, concentration quenching occurs due to excess energy transfer, so that intensity of luminescence decreases. Further, both maximum integrated area of emission spectrum and brightness appear at 1 mol %.

FIG. 10 shows the C.I.E. chromaticity coordinate of SrGe₄O₉:Mn⁴⁺ phosphor composition. As can be seen, a series of SrGe₄O₉ samples are excited with 419 nm. Coordinate value of black dot is (0.73, 0.26). Chromaticity coordinate value is not affected in dopant concentration ranging from 0.15 to 2.5 mol %, and color saturation is much better than current commercial product Y₂O₂S:Eu³⁺ (0.64, 0.35).

Table 2 shows comparison of chromaticity coordinate values of SrGe₄O₉:Mn⁴⁺ phosphor compositions doped with various concentrations of Mn⁴⁺.

TABLE 2
Mn4+ mol %	x ordinate value	y ordinate value
0.15	0.73	0.26
0.25	0.73	0.26
0.5	0.73	0.26
1.0	0.73	0.26
1.5	0.73	0.26
2.0	0-73	0.26
2.5	0.73	0.26

Composition 3

(Physical Property of Mg₂TiO₄:Mn⁴⁺ Phosphor Composition)

FIG. 11 shows comparison of XRD profiles from Mg₂TiO₄:Mn⁴⁺ phosphor compositions synthesized at various temperatures. Mg₂TiO₄:Mn⁴⁺ phosphor composition was successfully synthesized at as high as 1300° C. Though crystallinity of products obtained at 1400 and 1500° C. was higher, data from Inorganic Crystal Structure Database (ICSD) confirmed intensity ratio among various diffraction peaks is close to that obtained at 1300° C., thus preferred synthesis temperature is 1300° C.

FIGS. 12A and 12B show the XRD profiles from a series of Mg₂TiO₄:Mn⁴⁺ samples doped with various concentrations of Mn⁴⁺. Structure of Mg₂TiO₄:Mn⁴⁺ was not affected by Mn⁴⁺ in dopant concentration ranging from 0.05 to 2 mol %.

(Optical Property of Mg₂TiO₄:Mn⁴⁺ Phosphor Composition)

FIG. 13 shows the photoluminescence spectra of Mg₂TiO₄:Mn⁴⁺ phosphor composition synthesized at 1300° C. In dashed line part, small peak at 300 nm originates from charge transfer band of O₂-2p→Mn⁴⁺3d, and those at 352, 400 and 478 nm correspond to ⁴A₂→⁴T₁, ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂, respectively. Since ⁴A₂→²T₂ is spin-forbidden, it shows weaker intensity. Solid line at right hand represents emission spectrum mainly originating from ²E→⁴A₂.

FIG. 14 shows the concentration effect of Mg₂TiO₄:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺. Both intensity and integrated area of emission spectrum are highest at 0.25 mol %, but smooth at low concentration. Concentration quenching is found at concentration above 1 mol %.

FIG. 15 shows the C.I.E. chromaticity coordinates of Mg₂TiO₄:Mn⁴⁺ phosphor composition. As can be seen, ‘Δ’ represents chromaticity coordinate value of sample doped with 0.05˜1.0 mol % of Mn⁴⁺, (0.73, 0.26), which is nearly saturated; whereas ‘*’ represents that of doped with 1.5˜2.0 mol %. Similarly, chromaticity coordinate value of Mg₂TiO₄:Mn⁴⁺ phosphor composition doped with 0.05˜1.0 mol % is better than current commercial product Y₂O₂S:Eu³⁺ (0.64, 0.35).

Table 3 shows the comparison of chromaticity coordinate values of Mg₂TiO₄:Mn⁴⁺ phosphor compositions doped with various concentration of Mn⁴⁺.

TABLE 3
Mn4+ mol %	x ordinate value	y ordinate value
0.05	0.73	0.26
0.15	0.73	0.26
0.25	0.73	0.26
0.5	0.73	0.26
1.0	0.73	0.26
1.5	0.65	0.28
2.0	0.65	0.28

Composition 4

(Physical Property of Zn₂TiO₄:Mn⁴⁺ Phosphor Composition)

Structure of Zn₂TiO₄:Mn⁴⁺ is the same as that of above Mg₂TiO₄:Mn⁴⁺. FIG. 16 shows the comparison of XRD profiles from Zn₂TiO₄:Mn⁴⁺ phosphor compositions synthesized at various temperatures. Though Zn₂TiO₄:Mn⁴⁺ phosphor composition can be synthesized at about 1200° C., those obtained at 1300° C. is of best crystallinity and purity. Crystallinity of product obtained at 1400° C. is lower. Further, FIGS. 17A and 17B show XRD spectra from a series of Zn₂TiO₄:Mn⁴⁺ samples doped with various concentrations of Mn⁴⁺. Structure of Zn₂TiO₄:Mn⁴⁺ is not affected by Mn⁴⁺ in dopant concentration ranging from 0.05 to 2 mol %.

(Optical Property of Zn₂TiO₄:Mn⁴⁺ Phosphor Composition)

FIG. 18 shows the photoluminescence spectra of Zn₂TiO₄:Mn⁴⁺ phosphor composition synthesized at 1300° C. Dashed line at left hand represents excitation spectrum, wherein peak at 300 nm originates from charge transfer band of O²⁻2P→Mn⁴⁺3d, and those at 362 and 486 nm correspond to ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂, respectively. Solid line at right hand represents emission spectrum, wherein emission intensity at 672 nm in red area is highest.

FIG. 19 shows the concentration effect of Zn₂TiO₄:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺. Intensity of luminescence spectrum increases as dopant concentration is increased, reaches highest at 0.5 mol % and then drops down.

FIG. 20 shows the C.I.E. chromaticity coordinates of Zn₂TiO₄:Mn⁴⁺ phosphor composition. As can be seen, ‘Δ’ represents chromaticity coordinate value of sample doped with 0.25˜1.0 mol % of Mn⁴⁺, ‘*’ represents that of doped with 0.05˜0.15 mol %, ‘□’ represents that of doped with 1.5 mol %, and ‘’ represents that of doped with 2.0 mol %. The best Zn₂TiO₄:Mn⁴⁺ phosphor composition is obtained when doped with 0.25˜1.0 mol % of Mn⁴⁺. Chromaticity coordinate value decreases when shifting to left, and composition becomes less saturated. Also, ‘∘’ represents chromaticity coordinate value of current commercial product Y₂O₂S:Eu³⁺.

Table 4 shows the comparison of chromaticity coordinate values of Zn₂TiO₄:Mn⁴⁺ phosphor compositions doped with various concentrations of Mn⁴⁺.

TABLE 4
Mn4+ mol %	x ordinate value	y ordinate value
0.05	0.72	0.26
0.15	0.72	0.26
0.25	0.72	0.27
0.5	0.72	0.27
1.0	0.72	0.27
1.5	0.71	0.26
2.0	0.7	0.26

Composition 5

(Physical Property of SrMgAl₁₀O₁₇:Mn⁴⁺ Phosphor Composition)

As can be seen in FIG. 16, the best synthetic temperature for SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition is 1600° C., though SrMgAl₁₀O₁₇:Mn⁴⁺ crystallization phase forms starting at 1300° C. In according with the theory that crystallinity of phosphor composition is proportional to intensity, although the best synthetic temperature for SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition is above 1700° C. in prior document (N. Iyi and M. Gobbels, J. Solid State Chem., 122, 46, 1996), it can only be reached at 1600° C. in the present invention due to limitation of power of used high temperature oven.

FIGS. 22A and 22B show the XRD profiles from a series of SrMgAl₁₀O₁₇:Mn⁴⁺ samples doped with various concentration of Mn⁴⁺. Crystallinity is affected by Mn⁴⁺ in dopant concentration above 1.5 mol %.

(Optical Property of SrMgAl₁₀O₁₇:Mn⁴⁺ Phosphor Composition)

FIG. 23 shows the photoluminescence spectra of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor. Dashed line at left hand represents excitation spectrum, wherein absorption peak at 340 nm originates from ⁴A₂→⁴T₁, and small peaks at 396 and 468 nm correspond to ⁴A₂→²T₂ and ⁴A₂→⁴T₂, respectively. Solid line at right hand represents emission spectrum, wherein peak at 658 nm originates from red emission of 2E→⁴A₂.

FIG. 24 shows the comparison of emission intensity of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition doped with various concentration of Mn⁴⁺. Both intensity and integrated area of peak at 658 nm are highest at 0.25 mol %.

FIG. 25 shows C.I.E. chromaticity coordinates of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition. As can be seen, ‘Δ’ represents chromaticity coordinate value of red emission wavelength at 658 nm from SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor composition excited by 340 nm, (0.73, 0.27), which is saturated. Table 5 shows comparison of chromaticity coordinate values of SrMgAl₁₀O₁₇:Mn⁴⁺ phosphor compositions doped with various concentrations of Mn⁴⁺; chromaticity coordinate value is not affected in dopant concentration of 0.05˜1.5 mol %.

TABLE 5
Mn4+ mol %	x ordinate value	y ordinate value
0.05	0.73	0.27
0.15	0.73	0.27
0.25	0.73	0.27
0.5	0.73	0.27
1.0	0.73	0.27
1.5	0.73	0.27

Composition 6

(Physical Property of Y₃Ga₅O₁₂:Mn⁴⁺ Phosphor Composition)

Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition is prepared by solid state synthesis. As can be seen in FIG. 26, Y₃Ga₅O₁₂ crystalline phase forms as synthetic temperature reaches 1100° C.; best crystallinity is obtained at 1400° C.; and fused glassy product is obtained at 1500° C. Therefore, the best synthetic temperature for the present Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition is 1400° C.

FIGS. 27A and 27B show XRD profiles from a series of Y₃Ga₅O₁₂:Mn⁴⁺ samples doped with various concentrations of Mn⁴⁺. As can be seen, structure is not affected by introduction of Mn⁴⁺ ion.

(Optical Property of Y₃Ga₅O₁₂:Mn⁴⁺ Phosphor Composition)

FIG. 28 shows the photoluminescence spectra of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition synthesized. In dashed line part at left hand, absorption peak at 293 nm originates from charge transfer band of O²⁻2P→Mn⁴⁺3d, and those at 395 and 492 nm correspond to ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂, respectively. In solid line part at right hand, emission peaks in 600˜750 nm originate from ²E→⁴A₂.

FIG. 29 shows the comparison of intensity and integrated area of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition doped with various concentrations of Mn⁴⁺. As can be seen, maximum is obtained at 0.25 mol %.

FIG. 30 shows the C.I.E. chromaticity coordinate of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor composition, wherein ‘Δ’ represents the best chromaticity coordinate value of sample doped with 0.25 mol % of Mn⁴⁺, (0.72, 0.27), ‘*’ represents that of doped with 0.15 mol %, and ‘□’ represents that of doped with 0.5˜1.5 mol %. The best sample is obtained at 0.25 mol %.

Table 6 shows the comparison of chromaticity coordinate values of Y₃Ga₅O₁₂:Mn⁴⁺ phosphor compositions doped with various concentration of Mn⁴⁺.

TABLE 6
Mn4+ mol %	x ordinate value	y ordinate value
0.05	0.68	0.28
0.15	0.7	0.27
0.25	0.72	0.27
0.5	0.68	0.28
1.0	0.68	0.28
1.5	0.68	0.28

As described above, the present invention provides Mg₁₄Ge₅O₂₄:Mn⁴⁺, SrGe₄O₉:Mn⁴⁺, Mg₂TiO₄:Mn⁴⁺, Zn₂Ti_(1-d)O₄:Mn⁴⁺, SrMgAl₁₀O₁₇:Mn⁴⁺, and Y₃Ga₅O₁₂:Mn⁴⁺ phosphor compositions which are useful for the present light emission device. Best compositional ratio, physical and optical properties of the present phosphor compositions are shown in Table 7.

	TABLE 7
	Optical Property
Composition	Chemical		Synthesis	C.I.E.
No.	Formula	Compositional Ratio	Temp.	Coordinate	Wavelength
1.	Mg14Ge5O24	Mg14(Ge4.9875Mn0.0125)O2	1200° C.	0.73, 0.27	λem = 659 nm
					λex = 419 nm
2.	SrGe4O9	Sr(Ge3.96Mn0.04)O9	1100° C.	0.73, 0.26	λem = 655 nm
					λex = 290 nm
3.	Mg2TiO4	Mg2(Ti0.9975MN0.0025)O4	1300° C.	0.73, 0.26	λem = 656 nm
					λex = 352 nm
4.	Zn2TiO4	Zn2(Ti0.995Mn0.005)O4	1300° C.	0.72, 0.27	λem = 675 nm
					λex = 362 nm
5.	SrMgAl10O17	SrMg(Al9.975Mn0.025)O17	1600° C.	0.73, 0.27	λem = 658 nm
					λex = 340 nm
6.	Y3Ga5O12	Y3(Ga4.9875Mn0.0125)O12	1400° C.	0.72, 0.27	λem = 673 nm
					λex = 373 nm

In the above table, λ_ex represents preferred excitation wavelength for phosphor composition, and λ_em represents emission wavelength of emitting light from phosphor composition. The present light emission device is consisted of above compositions. The present composition is of high red color saturation with C.I.E. chromaticity coordinate value of x ranging from 0.72 to 0.73 and y ranging from 0.26 to 0.27. Not only the present composition is useful as light source for blue-near ultraviolet LEDs, but also emission wavelength thereof at 660 nm is applicable to current commercial medical instruments, as well as many other applications.

The present invention is disclosed above with reference to the preferred embodiments; however, the embodiments are not used as limitation of the present. It is appreciated to those in this field that the variation and modification directed to the present invention not apart from the spirit and scope thereof can be made, and the scope of the present invention is covered in the attached claims.

Claims

1. A light emitting device comprising a semiconductor light source emitting radiation at about 250 to 500 nm; and a phosphor composition radiationally coupled to the semiconductor light source, wherein the phosphor composition is selected from the group consisting of Mg14Ge5O24:Mn4+, SrGe4O9:Mn4+, Mg2TiO4:Mn4+, Zn2TiO4:Mn4+, SrMgAl10O17:Mn4+, and Y3Ga5O12:Mn4+.

2. The light emitting device as described in claim 1, wherein the light source is a light emitting diode.

3. The light emitting device as described in claim 2, wherein the light emitting diode is a semiconductor comprising nitride.

4. The light emitting device as described in claim 1, wherein the light source is an organic light emitting device.

5. The light emitting device as described in claim 1, wherein the phosphor composition is coated on surface of the light source.

6. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Ge in Mg14Ge5O24:Mn4+ phosphor composition is 0.05˜1 mol %.

7. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Ge in SrGe4O9:Mn4+ phosphor composition is 0.25˜2 mol %.

8. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Ti in Mg2TiO4:Mn4+ phosphor composition is 0.05˜2 mol %.

9. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Ti in Zn2TiO4:Mn4+ phosphor composition is 0.05˜2 mol %.

10. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Al in SrMgAl10O17:Mn4+ phosphor composition is 0.05˜1.5 mol %.

11. The light emitting device as described in claim 1, wherein the ratio that Mn substitutes Ga in Y3Ga5O12:Mn4+ phosphor composition is 0.05˜1.5 mol %.

12. The light emitting device as described in claim 1, wherein the phosphor composition is excited by light from the semiconductor light source and emits light with C.I.E. chromaticity coordinate value of x ranging from 0.63 to 0.73 and y ranging from 0.26 to 0.34.

13. The light emitting device as described in claim 1, wherein the phosphor composition is excited by light from the semiconductor light source and emits light with wavelength of 600 to 680 nm.

14. A method of producing phosphor composition used in the light emitting device as described in claim 1, which is conducted by solid state synthesis at 1000˜1600° C.

15. The method as described in claim 14, wherein the reaction time is 6˜10 hours.

16. The method as described in claim 14, wherein Mg2TiO4:Mn4+ and Zn2TiO4:Mn4+ phosphor composition are further sintered at 490˜590° C. under oxygen.

17. The method as described in claim 16, wherein the reaction time for sintering is 14˜18 hours.