[Invention Title]

RAPID SOLID-STATE SYNTHESIS OF YTTRIUM ALUMINUM GARNET YELLOW-EMITTING PHOSPHORS

[Technical Field]

<i> The present invention related to the cost effective and rapid synthesis

+3

of cerium doped yttrium-aluminum garnet phosphor of Y3Al ₅ 0i2 ^: Ce composition by combustion synthesis process. Additionally, the present invention relates to reaction mixture, more specifically to the design of the mixture to be thermodynamical ly suitable for the production of cerium doped yttrium- aluminum garnet phosphors within seconds.

[Background Art]

<2> The yttrium-aluminum garnet phosphor known as YAG e (when activated by trivalent cerium) is a well-known phosphor used in the so-called "white LED" commercial market. In comparison with phosphors based on silicates, sulphates, nitridosi 1 icates, and oxonitridosi licates, YAG has a relatively high absorption efficiency of blue colored excitation radiation, high quantum efficiency (QE greater than about 90 percent), good stability in a high temperature and high humidity environment, and a broad emission spectrum.

<3> The synthesis methods of YAG powders can be classified as follows: conventional solid-state method, solvothermal method, sol-gel method, co- precipitation method, solution combustion synthesis method, flame-synthesis method, etc.

<4> The conventional solid-state method is the basic method for preparing yttrium-aluminum garnet based phosphors. This method produces high crystalline and micrometer size (5-25 /zm) powder. It is based on oxide and carbonate precursor materials and typically requires high calcination temperature (>1600 ^° C) in reducing atmosphere (N2/H2), and long reaction time

(5-10 hours). The improved solid-state reaction process which is associated with flux such as AIF3, BaF ₂ or YF3 can lower the sintering temperature down to 1500°Ο. The main disadvantages of this method are high energy and time consumpt ion.

<5> In the co-precipitation method firstly a precursor solution is prepared by dissolving and mixing required amount of the metal nitrates. Then, a defined amount of a dispersing agent (sodium dodecyl sulfate (SDS), EDTA, hexamethyldisi lazane (HMDS), etc.) is added to the mixed nitrites solution. The mixed solution of metal nitrates and dispersing agent is precipitated with ammonium hydrogen carbonate (or ammonium hydroxide) at 50-70 ^° C . The resultant precipitate is filtered, washed with distilled water and absolute alcohol in sequence, and then dried at 60 ^° C for one day. The dried cake, after being lightly crushed, is calcined at various temperatures from 800 to 1000°C for 2 h in air. This method produces wel 1-dispersed YAG powders with a particle size between 100 tO 500 nm. However the crystal 1 inity and emission intensity of YAG powder prepared by co-precipitation method is sufficiently low compared with solid-state method. Moreover, this method is more complicated and has low production efficiency.

<6> The sol-gel method is based on hydrolysis of precursor materials, which leads to amorphous precipitate formation. The precursor materials used in sol-gel method includes metal alkoxides, chlorides, oxides, citrates, etc. As-prepared gel, is dried at 80 to 100 ^° C and calcined at 1000 to 1500 ^° C temperature range to produce submicrometer size YAG phosphor. Sol-gel method has a same disadvantages as co-precipitation method and can not be considered as promising and competitive with solid-state method.

3+

<7> In ultrasonic spray pyrolysis method Ce -activated yttrium aluminum garnet powder was synthesized from metal nitrite precursor solution and ammonium hydroxide (or alkalimetal hydroxide). The precursor mixture is dried in air using a flow of carrier gas at the temperature between 200 and 900 ^° C . Then, the granulated particles were calcined at the temperature between 1300 and 1500 ^° C in the air for several hours to produce YAG powder. In flame pyrolysis technique urea as an additive, was added to the precursor nitrite solution and methane gas was used as the fuel with a flow rate of 5.5 L/min. To maintain a complete combustion reaction, oxygen was made to flow at 2.5 times the flow rate of methane gas. To produce a garnet structure, the as- prepared particles were heat treated in an electric furnace The heat treatment was carried out at a temperature approaching 1300 ^° C for 4 h at a heating rate of 1000 ^° C/h. After annealing was completed, particles were allowed to cool naturally. The as-prepared nanopart icles were hexagonal YA10 ₃ , and they can be converted to YAG e after being annealed at 1200 ^° C for 4h. This technique also is not time and energy saving, and YAG powder produced with this technique is badly agglomerated and shows low emission intensity. <8> Ce-doped YAG phosphor particles can be also synthesized by solvothermal method using the aqueous solutions of aluminum and yttrium salts mixed with ammonium hydrogen carbonate at room temperature. Then, the precipitate obtained is mixed with alcohol, placed in autoclave container, and heated to the desired temperature and kept at that temperature for several hours. During the reaction period, the pressure gradually increased up to 10 MPa. When the reaction was finished, it was cooled to room temperature. The resulting suspension was filtered; washed with distilled water and dried. As prepared powder is then calcined at high temperature (above 1000 ^° C) to produce YAG e phosphor. YAG e phosphor particles are basically spherical in shape, and a mean grain size about 60 nm. However, solvothermal method has a same disadvantages as others liquid phase methods, i.e. low yield, long processing time, multistage processes and expensive equipment.

[Disclosure]

[Technical Problem]

<9> Solution combustion synthesis method also is known for the preparation of YAG powders. The synthesis process involved the combustion of redox mixtures, in which metal nitrate acted as an oxidizing reactant and water soluble organic compound (carbohydrazide, urea, citriceacid, etc.) as a re ducing one. The initial composition of the solution containing metal nitrates and organic compounds is based on the total oxidizing and reducing valences of the oxidizer and the fuel using the concepts of the propel lant chemistry. Sometimes, a flux (LiF, NaF) also is used as a precursor material, to increase luminance of YAG. In this process stoichiometric amounts of oxidizing and reducing reactants are dissolved in deionized-dist i 1 led water followed heating procedure on a hot plate. Initially, the solution boils and undergoes dehydration followed by decomposition with the evolution of large amount of gases (NO, NH ₃ , CO, C0 ₂ , HNCO, etc.). After the solution reaches the point of spontaneous combustion, it begins burning and releases lots of heat, vaporizes all the solution instantly and becomes a solid burning. For instance, a stoichiometric combustion reaction of metal nitrates with carbohydrazide to from YAG is illustrated as follows:

<io> 3 Y(N0 ₃ ) ₃ + 5 A1(N0 ₃ ) ₃ + 15 C0(N ₂ H ₃ ) ₂ → WsOu + 15C0 ₂ + 45H ₂ 0 + 42N ₂ (1)

<ii> Further annealing of combustion products at 1000 to 1500 ^° C for several hours is required to increase the luminous intensity.

<i2> Solution-combustion method also has all characteristic disadvantages for wet chemistry methods: low yield, time and energy consumption, badly agglomerated powder, poor emission intensity.

<i3> For the reasons described above, novel and progressive methods for producing YAG:Ce based phosphors are urgently demanded. The problems include the design of the method and reaction mixture to be suitable for production of phase pure YAG:Ce yellow-emitting phosphor of high emission intensity within seconds.

[Technical Solution]

<14> It is primary object of the present invention to provide combustion process in mult i -component mixture consisting of metal oxides (Y ₂ 0 ₃ ,A1 ₂ 0 ₃ ) , cerium salt, inorganic oxidizer, carbon fuel and flux in room temperature for synthesizing YAG:Ce yellow-emitting phosphors within several or tens seconds. <15> It is another object of the present invention to provide reaction mixture which can be cost-effective, easy handling, and suitable for producing YAG:Ce yellow-emitting phosphors rapidly while requiring only a small amount of heat or energy to initiate them. <i6> It is still another object of the present invention to provide combustion reactions which can produce Y3A I 5O12 phase rapidly and in which the starting materials and their byproduct are chosen to be soluble in water and certain solvents so that they can be readily removed resulting YAG e yellow- emitting phosphors.

<17> It is still an additional object of the present invention to provide combustion reactions which can produce YAG e yellow-emitting phosphors having high-emission intensity, within seconds.

<i 8> It is yet another object of the present invention to provide reaction mixture, in which red-ox exothermic mixture of oxidizer-carbon fuel composition is additionally used to rapidly produce high combustion temperature, and phase pure yttrium-aluminum garnet of Y3A I 5O12 composition.

<i9> It is still yet an additional object of the present invention to provide reaction mixture, which contains flux, to produce phase pure YAG:Ce phosphors with improved photo luminance.

<20> In accordance with the present invention embodiment of the present invention are directed to the production process and the reaction mixture, for a large scale and a rapid synthesis of cerium doped yttrium-aluminum

+3

garnet (YsAlsO^ e , shortly YAG e) yellow-emitting phosphor. The basic process includes a first step of mixing of yttrium oxide (Y2O3 ) with aluminum oxide (A I 2O3 ) , one or two cerium containing inorganic salts, solid inorganic oxidizer, inorganic or organic carbon fuel and flux in a container. The process also includes a second step of forming the reaction pellet by hand compacting of reaction mixture into a quartz cup, loading of quartz cup into high pressure reactor and igniting the reaction mixture under the atmosphere of inert gas of 0.5 to 10 MPa. A solid reaction product consisted of YAG yellow-emitting phosphor along with potassium chloride is produced. The process further includes a third step of separating the nitride phosphor from the by-products by solvent extraction. <2i> More specifically, the present invention is a rapid sold-state process of synthesizing YAG e phosphor particles which comprises: of mixing of yttrium oxide (Y ₂ O ₃ ) with aluminum oxide (AI ₂ O3), cerium compounds, solid inorganic oxidizer, carbon fuel and flux, compacting the mixture into a quartz cup and combusting of reaction mixture under the atmosphere of inert gas by ignition, and purifying the combustion product with distillated water. The mixture which, optionally is in the powdered form, is ignited using any convenient ignition source such as a coil of nickel-chromium wire, or an electric arc and the like. Upon ignition, a combustion wave rapidly self- propagates through the reactants transforming them into the Y3Al ₅ 0i ₂ ^: Ce phosphor and potassium chloride.

<22> In this process, yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (AI ₂ O ₃ ) are mixed in a mole ratio of 1 : 1 to 2.

<23> The cerium compounds are inorganic salts containing one or two cerium, and preferably are represented in any available form of oxide, nitride, halide, acetate and so forth. More prefarably, the compounds are CeC>2 or CeF3.

+3 +3

The molar concentration of Ce is 0.01 to 0.05 on the basis of Y

<24> The solid inorganic oxidizer is metal chlorate, metal perchlorate or other inorganic oxidizer, which produce water soluble solid products and/or gas phase products after thermal decomposition. Prefarably, it is KC10 ₃ ,

NaC10 ₃ , KCIO ₄ , NH ₄ CIO ₄ and so forth. The molar concentration of oxidizer is between 1 and 3 mole to produce 1 mole of YAG e.

<25> The carbon fuel is a inorganic or organic compound having carbon atoms and producing heat during the combustion, and for example, black soot, charcoal, polyethylene ((C ₂ H ₄ ) _n ), urea (COCNh^), ascorbic acid (C ₆ H ₈ 0 ₆ ) and hexamethylenetetramine (C ₆ Hi ₂ N ₄ ) . The molar concentration of fuel is between 1 and 4 mole to 1 mole of the oxidizer.

<26> The flux is one or more selected from NH ₄ C1 , NH4F, YF ₃ , NaF, etc. In the present invetion, the flux is used as a source of hydrogen to accomplish Ce

+3

→Ce transformations in the combustion wave and also serves as a catalytic agent to produce a single phase yttrium-aluminum garnet, within seconds, due to formation of easy volatile metal fluorides, such as A1F ₃ , YF ₃ , CeF ₃ , etc., in the combustion wave.

<27> The inert gas is between 0.5 to 10 MPa, preferably about 2 to 5 MPa.

Preferably, argon, introgen, etc. can be used. The inert gas prevents unnecessary reactions with air adjacent to the reactant mixture in combustion process. Also, since gas resulting from the soild inorganic oxidizer strongly blows into the mixture, the inert gas of the above-mentioned pressure may prevent breakdown of pellets.

<28> The ignition of reaction mixture is performed by resist ively heated nickel-chromium wire, electric arc and the like, within 1 to 3 sec. The combustion temperature is between 1000 and 1600 ^° C .

<29> The purification of reaction product is performed with disti Hated water heated to 50-70 ^° C , or the disti Hated water after treatment of HC1 solution. The HC1 solution is used in about 5 to 10 % concentration and can remove the small amount of existing Ce0 ₂ after the combustion process and KC1 strongly adhered to surface of YAG particles.

<30> Combustion synthesis method of YAG e powder involves two main sequential chemical reactions. At first, KC10 ₃ reacts with carbon after a local ignition of pellet. This reaction is highly exothermic and gives off 152.55 kcal/mol heats according to the equation given below:

<31> KCIO3 + 1.5 C → KC1 + 1.5 C0 ₂ + AHreaction (2)

<32> ^" 152.55 kcal/mol

<33> Due to the heat generated by (2), the temperature of the reaction pellet increases rapidly to 1000 to 1600 ^° C , leading to the formation of YAG:Ce phosphor: < > 1.5 Y ₂ - _x 0 ₃ + 2.5 A1 ₂ 0 ₃ + xCe0 ₂ → Y ₃ -xCe _x Al ₅ 0i ₂ (3)

<35> The concentration of KC10 ₃ + 1.5 C exothermic mixture is critical for the synthesis of phase pure YAG e powder through the combustion process. According to our experimental results, the optimum concentration of KC10 ₃ +

1.5 C mixture is about 2.5 to 3.0 mole per one mole of YAG product. If it is lower than this concentration, the starting materials are incompletely transformed into the Y ₃ - _x Ce _x Al ₅ 0 ₁₂ phase and result in YA10 ₃ impurity.

[Advantageous Effects]

+3

<36> A cerium doped yttrium-aluminum garnet phosphor of Y ₃ Al ₅ 0i ₂ :Ce composition can be synthesized cost-effectively and rapidly by a combustion synthesis process of the present invention.

[Description of Drawings]

<37> Fig.l shows X-ray di ffract ion(XRD) pattern (a) and scanning electron

microscopy(SEM) micrograph (b) of YAG e phosphor prepared according to Example 1.

<38> Fig.2 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 2.

<39> Fig.3 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 3.

<40> Fig.4 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 4.

<4i> Fig.5 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 5.

<42> Fig.6 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 6.

<43> Fig.7 shows XRD pattern (a) and SEM micrograph (b) of YAG ^' -Ce phosphor

prepared according to Example 7.

<44> Fig.8 shows XRD pattern (a) and SEM micrograph (b) of YAG e phosphor

prepared according to Example 8. <45> Fig.9 shows XRD pattern (a) and SEM micrograph (b) of YAG- ^' Ce phosphor

prepared according to Example 9.

<46> Fig.10 shows XRD pattern (a) and SEM micrograph (b) of YAG- ^' Ce phosphor

prepared according to Example 10.

<47> Fig.11 shows XRD pattern (a) and SEM micrograph (b) of YAG- ^' Ce phosphor

prepared according to Example 11.

[Mode for Invention]

<48> The invention is further illustrated by the following examples.

<49> EXAMPLE 1

<50> Rapid Solid-State Synthesis of yellow-emitting yttrium-aluminum garnet

<51>

<52> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ O3) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.44 gram of cerium oxide (CeC^), 15.3 gram of potassium chlorate (KC10 ₃ ), and 2.25g black soot. The reactant mixture was hand compacted in a 35 millimeter in diameter

3 quartz container. The experimental density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ πι in diameter) coated by thin layer of AI 2O3 , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water, dried and then ground with a mortar and pestle.

<53>

<54> Combustion temperature, ^° C - 1500 + 50

<55> Phase composition (X-ray diffraction, XRD)- Y3A I 5O12 , YA10 ₃

<56> Photo luminescence(PL) intensity (compared with reference) - 45 %

<57> <58> EXAMPLE 2

<59> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<60>

<6i> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ 0 ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.44 gram of cerium oxide (Ce0 ₂ ), 15.3 gram of potassium chlorate (KCIO3), 2.25g black soot and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental density of the

3

pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and 100zm in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water, dried and then ground with a mortar and pest le.

<62>

<63> Combustion temperature, ^° C - 1500 + 50

<64> Phase composition (XRD)- Y ₃ A1 ₅ 0 ₁₂

<65> PL intensity (compared with reference) - 60 %

<66>

<67> EXAMPLE 3

<68> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<69>

<70> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ 0 ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.66 gram of cerium oxide (CeC^), 15.3 gram of potassium chlorate (KC10 ₃ ), 2.25g black soot and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental density of the

3

pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ ιη in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1, washed with distilled water, dried and then ground with a mortar and pest le.

<71>

<72> Combustion temperature, ^° C - 1500 + 50

<73> Phase composition (XRD)- Y ₃ AI ₅ O ₁₂

<74> PL intensity (compared with reference) - 75 %

<75>

<76> EXAMPLE 4

<77> Rapid Solid-State Synthesis of yellow-emitting yttrium-aluminum garnet

<78>

<79> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ O ₃ ) with 12.9 gram of aluminum oxide (AI ₂ O3), 0.8 gram of cerium oxide (CeC^), 15.3 gram of potassium chlorate ( CIO ₃ ) , 2.25g black soot and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental density of the

3

pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and lOOjum in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water, dried and then ground with a mortar and pest le.

<80>

<8i> Combustion temperature, ^° C - 1500 + 50

<82> Phase composition (XRD)- Y ₃ AI ₅ O ₁₂

<83> PL intensity (compared with reference) - 80 %

<84>

<85> EXAMPLE 5

<86> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<87>

<88> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ O ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.5 gram of cerium oxide (CeC^), 15.3 gram of potassium chlorate (KCIO3), 2.25g charcaol and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental density of the

3

pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and lOOjum in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1, washed with distilled water, dried and then ground with a mortar and pestle.

<89>

<90> Combustion temperature, ^° C - 1500 + 50 <9i> Phase composition (XRD)- Y3AI5O12, YA10 ₃

<92> PL intensity (compared with reference) - 65 %

<93>

<94> EXAMPLE 6

<95> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<96>

<97> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y2O3) with 12.9 gram of aluminum oxide (A I 2O3 ) , 0.8 gram of cerium oxide (Ce0 ₂ ), 15.3 gram of potassium chlorate (KC10 ₃ ), 2.25g charcaol and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental density of the

3

pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ ιη in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water, dried and then ground with a mortar and pest le.

<98>

<99> Combustion temperature, ^° C - 1500 + 50

<ioo> Phase composition (XRD)- Y3A I 5O12

<ioi> PL intensity (compared with reference) - 80 %

<102>

<i03> EXAMPLE 7

<i 04> Rapid Solid-State Synthesis of yellow-emitting yttrium-aluminum garnet

<105>

<106> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ 0 ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.80 gram of cerium oxide (Ce0 ₂ ), 15.3 gram of potassium chlorate (KCIO ₃ ), 2.5g polyethylene (C ₂ H4) _n and 1.5g ammonium fluoride (NH ₄ F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The

₃

experimental density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and 100//m in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water, dried and then ground with a mortar and pestle.

<107>

<108> Combustion temperature, ^° C - 1400 + 50

<i09> Phase composition (XRD)- YsAl ₅ 0i ₂

<iio> PL intensity (compared with reference) - 75 %

<111>

<ii2> EXAMPLE 8

<ii3> Rapid Solid-State Synthesis of yellow-emitting yttrium-aluminum garnet

<114>

<ii5> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y ₂ 0 ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.80 gram of cerium oxide (Ce0 ₂ ), 15.3 gram of potassium chlorate (KCIO3), 9.0g hexamethylenetetramine (C ₆ Hi ₂ N ₄ ) and 1.5g ammonium fluoride (NH ₄ F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz

3

container. The experimental density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel-chromium coil; ignition was achieved using power input into the nickel-chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten-rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ ιη in diameter) coated by thin layer of AI ₂ O3, were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HCl, washed with distilled water, dried and then ground with a mortar and pestle.

<116>

<i)7> Combustion temperature, ^° C - 1400 + 50

<ii8> Phase composition (XRD)- Y3AI5O12

<ii9> PL intensity (compared with reference) - 70 %

<120>

<i2i> EXAMPLE 9

<i22> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<123>

<i24> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Υ ₂ 0 ₃ ) with 12.9 gram of aluminum oxide (A1 ₂ 0 ₃ ), 0.80 gram of cerium oxide (CeC , 15.3 gram of potassium chlorate (KCIO ₃ ), 9.0g urea

(C0(NH ₂ ) ₂ ) and 1.5g ammonium fluoride (NH4F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental

3

density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel- chromium coil; ignition was achieved using power input into the nickel- chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten- rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ ιη in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HCl, washed with distilled water, dried and then ground with a mortar and pestle. <125>

<126> Combustion temperature, ^° C - 1100+50

<i27> Phase composition (XRD)- Y3A I 5O12

<128> PL intensity (compared with reference) - 100 %

<129>

<i3o> EXAMPLE 10

<i3i> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet

<132>

<i33> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y2O3) with 12.9 gram of aluminum oxide (AI2O3), 0.80 gram of cerium oxide (Ce0 ₂ ), 18.4 gram of potassium chlorate (KCIO3), 10.8g urea

(C0(NH ₂ )2) and 1.5g ammonium fluoride (NH ₄ F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental

3

density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel- chromium coil; ignition was achieved using power input into the nickel- chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten- rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and 100zm in diameter) coated by thin layer of A1 ₂ 0 ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HC1 , washed with distilled water,dried and then ground with a mortar and pestle.

<134>

<135> Combustion temperature, ^° C - 1200+50

<136> Phase composition (XRD)- Y3A I 5O12

<i37> PL intensity (compared with reference) - 95 %

<138>

<i39> EXAMPLE 11

<140> Rapid Sol id-State Synthesis of yellow-emitting yttrium-aluminum garnet <141>

<142> A polymer bottle with zirconia balls was used to mix 16.8 gram powder of yttrium oxide (Y2O3 ) with 12.9 gram of aluminum oxide (AI ₂ O ₃ ), 0.60 gram of cerium oxide (Ce(¼), 18.4 gram of potassium chlorate ( C10 ₃ ), 10.8g urea

(C0(NH2) ₂ ) and 1.5g ammonium fluoride (NH ₄ F). The reactant mixture was hand compacted in a 35 millimeter in diameter quartz container. The experimental

3

density of the pellets was l.Og/cm . The metallic cup with green mixture was loaded into the combustion chamber by placing it directly on top of a nickel- chromium coil; ignition was achieved using power input into the nickel- chromium coil in a high-purity argon atmosphere of 2.0 MPa. Two tungsten- rhenium thermocouples (W/Re-5 vs W/Re-20, 50 and ΙΟΟ πι in diameter) coated by thin layer of AI ₂ O ₃ , were used for combustion temperature and wave velocity measurements. The resulting yellowish product was first treated with 1-2 percent solution of HCl, washed with distilled water, dried and then ground with a mortar and pestle.

<143>

<144> Combustion temperature, ^° C - 1200 + 50

<145> Phase composition (XRD)- Y3AI5O ₁₂

<146> PL intensity (compared with reference) - 105 %

[Table 11

pharacteristics of YAG samples

From the measured Photo luminescence(PL) values, it can be understood that the emission intensity of prepared YAG powder is greater than 100% with increase of the density in comparison to a standard sample, and also, compared to standard sample from the color coordinate, an error range of both x and y are within 0 to 0.01 and therefore yellowish light having the same series as that of standard sample is emitted. Also, from the analyzed results of the measured X ^~ ray dif fract ion(XRD) and scanning electron microscopy(SEM) , it can be understood that YAG powder is produced as a single phase and has good dispersion and 3 to 15 μιη of particle sizes.

From the foregoing it can be seen that a process for producing the phosphor material has been described. Accordingly it is intended that the foregoing disclosure shall be considered only as an illustration of the principle of the present invention.