A process of synthesizing a yttrium aluminum garnet (YAG) powder. The process comprises introducing powders of yttria and silica to form a powder mixture, wherein alumina is not added to the powder mixture. Milling the powder mixture in the presence of an alumina grinding media and a solvent forms a powder slurry. Processing the powder slurry forms a green compact. Calcining the green compact at a temperature of from 1100° C. to 1650° C. for greater than 8 hours in air to 50% or less theoretical density forms a YAG compact of at least 92 wt % Y.sub.3Al.sub.5O.sub.12. Milling the YAG compact, without a grinding media, and drying produces the YAG powder. Processes further include introducing a dopant to the powder mixture to produce doped YAG powder.

A ceramic composite having a phosphor particle and a coating layer on the surface of the phosphor particle, in which a matrix crystal structure of the phosphor particle and the coating layer have identical garnet structures, and the thickness of the coating layer is greater than or equal to 0.001 μm and smaller than or equal to 0.450 μm.

A ceramic composite having a phosphor particle and a coating layer on the surface of the phosphor particle, in which a matrix crystal structure of the phosphor particle and the coating layer have identical garnet structures, and the thickness of the coating layer is greater than or equal to 0.001 μm and smaller than or equal to 0.450 μm.

A single-mode crystal fiber is provided. The fiber has a core. The core is made of a crystalline material with a melting point above 1900 degrees Celsius (° C.). The core has a coat. The coat is made of a crystalline material the same as that of the core. Through immersion plating under a low vacuum pressure and a high temperature, the material of the coat is sintered to form an outer layer covering the core. Thus, the thickness of the coat is controlled. A single crystal totally the same as that of the core is grown in a solid state with no ceramics contained. Consequently, the crystal contains no ceramics; and, through being sintered in a vacuum environment, the crystal has pores the smallest in size and the fewest in number, as compared to those sintered under a normal pressure.

A single-mode crystal fiber is provided. The fiber has a core. The core is made of a crystalline material with a melting point above 1900 degrees Celsius (° C.). The core has a coat. The coat is made of a crystalline material the same as that of the core. Through immersion plating under a low vacuum pressure and a high temperature, the material of the coat is sintered to form an outer layer covering the core. Thus, the thickness of the coat is controlled. A single crystal totally the same as that of the core is grown in a solid state with no ceramics contained. Consequently, the crystal contains no ceramics; and, through being sintered in a vacuum environment, the crystal has pores the smallest in size and the fewest in number, as compared to those sintered under a normal pressure.

In an embodiment a conversion element includes a first phase and a second phase, wherein the first phase comprises lutetium, aluminum, oxygen and a rare-earth element, wherein the second phase comprises Al.sub.2O.sub.3 single crystals, and wherein the conversion element comprises at least one groove.

In an embodiment a conversion element includes a first phase and a second phase, wherein the first phase comprises lutetium, aluminum, oxygen and a rare-earth element, wherein the second phase comprises Al.sub.2O.sub.3 single crystals, and wherein the conversion element comprises at least one groove.

An α-sialon phosphor particle containing Eu. At least one slit is formed on a surface of the α-sialon phosphor particle. The α-sialon phosphor particle is preferably produced by undergoing a raw material mixing step, a heating step, a pulverizing step, and an acid treatment step.

An α-sialon phosphor particle containing Eu. At least one slit is formed on a surface of the α-sialon phosphor particle. The α-sialon phosphor particle is preferably produced by undergoing a raw material mixing step, a heating step, a pulverizing step, and an acid treatment step.

A method for producing a solid composition according to the present disclosure includes producing an oxide to be converted into a first functional ceramic by reacting with an oxoacid compound, and mixing the oxide, the oxoacid compound, and a second functional ceramic that is different from the first functional ceramic. The oxoacid compound preferably contains at least one of a nitrate ion and a sulfate ion as an oxoanion.