Sintering Aid Coated YAG Powders and Agglomerates and Methods for Making

Abstract

Particles including a YAG core and a coating of sintering aid deposited thereon. The particles and agglomerates thereof maybe formed as a powder. The coated YAG-containing particles are well-suited to production of polycrystalline YAG-containing ceramics. The coated YAG-containing particles may be fabricated using a novel fabrication method which avoids the need for formation of a homogeneous powder mixture of YAG and sintering aid. In the method, a solution including a sintering aid or sintering aid precursor is prepared and mixed with YAG-containing particles to form a mixture. The mixture may be sprayed into a drying column and dried to produce coated particles. Alternatively, the YAG particles and sintering aid or sintering aid precursor solution may be separately introduced to the drying column and dried to form coated YAG-containing particles.

1 . A coated particle comprising:
 a core comprising YAG; and   a sufficient amount of a sintering aid coated on a surface of said core, wherein the coating is sufficiently continuous to substantially prevent a large number of sites where another core may come into contact with the coated YAG-containing core.   
     
     
         2 . The particle according to  claim 1 , wherein said core further comprises a rare earth element dopant. 
     
     
         3 . The particle according to  claim 2 , wherein said rare earth element dopant is selected from the group consisting of Yb, Nd, Er and combinations thereof. 
     
     
         4 . The particle according to  claim 2 , wherein said core comprises less than about 10% by weight of the dopant. 
     
     
         5 . The particle according to  claim 2 , wherein said core comprises from about 1% to about 2% by weight of the dopant. 
     
     
         6 . The particle according to  claim 1 , wherein the sintering aid comprises a material selected from the group consisting of: silicon dioxide, fluoride salt, magnesium oxide and combinations thereof. 
     
     
         7 . The particle according to  claim 6 , wherein the fluoride salt is selected from the group consisting of aluminum fluoride and lithium fluoride. 
     
     
         8 . The particle according to  claim 6 , wherein the sintering aid is silica. 
     
     
         9 . The particle according to  claim 1 , wherein said core has a diameter of from about 10 nanometers to about 100 microns and wherein said coating has a thickness of from about 1 nanometer to about 500 microns. 
     
     
         10 . A method for forming a coated particle comprising YAG, said method comprising the steps of:
 preparing a solution comprising a sintering aid or sintering aid precursor;   mixing YAG-containing particles with said solution to form a slurry; and   drying said mixture to form YAG-containing particles with a coating of sintering aid on a surface thereof.   
     
     
         11 . The method of  claim 10 , wherein said sintering aid precursor is a silica precursor. 
     
     
         12 . The method of  claim 11 , wherein said silica precursor is selected from the group consisting of: tetraethoxysilane, tetramethoxysilane, alkoxy silanes, silicate oxides and combinations thereof. 
     
     
         13 . The method of  claim 10 , wherein said drying step is carried out at a temperature of from about 200° C. to about 500° C. 
     
     
         14 . The method of  claim 10 , wherein said drying step gradually increases temperature from a first temperature to a higher temperature. 
     
     
         15 . The method of  claim 14 , wherein said YAG particles comprise a dopant. 
     
     
         16 . The method of  claim 15 , wherein said dopant is selected from the group consisting of Yb, Nd, Er and combinations thereof. 
     
     
         17 . The method of  claim 10 , wherein the YAG-containing particles are mixed with the sintering aid solution to form a slurry and said slurry is sprayed into a drying column for said drying step. 
     
     
         18 . The method of  claim 10 , wherein the YAG-containing particles are provided to said drying step separately from said sintering aid solution. 
     
     
         19 . The method of  claim 10 , wherein said sintering aid comprises a material selected from the group consisting of: silicon dioxide, fluoride salt, magnesium oxide and combinations thereof. 
     
     
         20 . The method of  claim 15 , further comprising the step of heat treating said coated YAG-containing particles to fabricate a transparent, shaped polycrystalline YAG ceramic.