| 摘要 |
A process for producing an ultrapure rare earth oxide phosphor from partially purified raw materials is disclosed that comprises forming an acidic aqueous solution comprising water, a mineral acid, europium and a second rare earth element selected from the group consisting of yttrium, gadolinium and mixtures thereof having a relatively minute amount of an impurity selected from the group consisting of cerium, thorium and mixtures thereof, maintaining the solution under controlled pH and temperature condition, adding to the solution a controlled amount of a water-soluble persulfate source to thereby form a solid and liquid phase, separating the phases and adding oxalic acid to the liquid phase to form a rare earth oxalate and converting the oxalate to the corresponding rare earth phosphor selected from the group consisting of rare earth oxides and rare earth oxysulfides.
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