oxygen(2-);yttrium(3+)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In order to remove the excess yttrium oxide and phosphoric acid from the solids in the slurry, a small amount of an inorganic acid is added to the slurry. The acid releases the yttrium compound and phosphoric acid from the yttrium phosphate and allows them to react on their own until the phosphoric acid is consumed. The 1.5 molar percent excess of the yttrium compound reacts with the acid to form a soluble yttrium salt which dissolves in the aqueous phase of the slurry. When yttrium oxide is used as the yttrium compound and nitric acid is used as the inorganic acid, the reaction provides soluble yttrium nitrate which combines with the remaining phosphoric acid to produce yttrium phosphate solids and with minor amounts of yttrium nitrate in solution. dissolves in the aqueous phase of the slurry

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. maintained at a temperature that typically ranges between about 20° C. and about 70° C

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixed rare earth nitrate aqueous solution was prepared by dissolving 94.5 g of yttrium oxide and 5.5 g of europium oxide in 200 ml of a concentrated nitric acid followed by the addition of water to make up a volume of 3.3 liters. Separately, an aqueous ammoniacal oxalic acid solution was prepared by dissolving 240 g of oxalic acid dihydrate in 6.6 liters of water and adding 290 ml of a 28% ammonia water thereto. The mixed rare earth nitrate solution cooled to room temperature was added gradually to this oxalic acid solution under agitation at room temperature taking 20 minutes and agitation was further continued for additional 10 minutes. The pH value of the aqueous medium was 2.0. The precipitate thus formed was collected by filtration under suction and repeatedly washed with deionized water until no nitrate ions could be detected in the washing taking 1.5 hours as measured from the start of the precipitation reaction. The precipitate after washing was added to 8 liters of deionized water at 50° C. and dispersed therein by agitation and the dispersion was agitated for 4 hours at 60° C. The dispersion was filtered to collect the precipitate which was dried and calcined for 2 hours at 900° C. to give a powder of mixed rare earth oxide of yttrium and europium. This oxide powder was examined by the scanning electron microscopy to find that the particles mostly has a polyhedral configuration. The powder had a specific surface area of 6.8 m2 /g as determined by using an instrument Flow Souve 2300 (manufactured by Micromeritex Co.), an average particle diameter of 1.71 μm as determined by using a Fischer Subsieve Sizer Model 95 (manufactured by Fischer Co.) and a QD value of 0.20 calculated from a cumulative particle volume distribution curve prepared by using the histogram of the volume fractions of particles obtained by using a Coulter Model TA-II (manufactured by Coulter Electronics Co.) and shown in FIG. 1 of the accompanying drawing. agitation was further continued for additional 10 minutes The precipitate thus formed was collected by filtration under suction repeatedly washed with deionized water until no nitrate ions taking 1.5 hours as measured from the start of the precipitation reaction The precipitate after washing was added to 8 liters of deionized water at 50° C. dispersed The dispersion was filtered to collect the precipitate which was dried calcined for 2 hours at 900° C.