Phosphoric Acid → Yttrium oxide

Generally, a 75 to 85 weight percent solution of phosphoric acid is added to the slurry over a period of about 15 minutes to about 90 minutes as the slurry is continuously agitated and maintained at a temperature that typically ranges between about 20° C. and about 70° C. The amount of the phosphoric acid added to the slurry is usually about 1.5 molar percent less than the amount of the yttrium compound present in the slurry. When the yttrium compound used is yttrium oxide, the reaction takes place to form yttrium phosphate, minor amounts of yttrium oxide, minor amounts of surface adsorbed phosphoric acid and water. The yttrium phosphate formed comprises approximately 95.5 percent of the solids portion in the slurry.