CERIUM AND/OR TERBIUM PHOSPHATE OPTIONALLY WITH LANTHANUM, PHOSPHOR RESULTING FROM SAID PHOSPHATE A

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The invention relates to a rare earth (Ln) phosphate, Ln being either at least one rare earth selected from cerium and terbium, or lanthanum in combination with at least one of the two above-mentioned rare earths, that has a crystalline structure of the monazite type with a potassium content of 6000 ppm at most. The phosphate is obtained by the precipitation of a rare earth chloride at a constant pH lower than 2, by calcination at a temperature of at least 700°C and by redispersion in hot water. The invention also relates to a phosphor obtained by the calcination at at least 1000°C of said phosphate.