Rare earth or rare earth metal vanadate phosphor purificn. - by heating with soda or potash removes impurities concn. on surface

摘要

Removal of impurities conc. on the surface of particles of phosphors (I) involves heating to 150-1250, (850-1000) degrees C with soda and/or potash (II), cooling and treating with a solvent (water) for (II). The mixt. pref. also contains an oxidant, e.g. KNO3, (NH4)2S2O8, perborate, percarbonate etc. and/or a glass former, e.g. borate, silicate, phosphate etc. Red phosphors used in colour TV tubes can be obtd. in a purity high enough for re-use without complete decompsn. and re-synthesis. Heating is carried out for 10 min to 10 h (1-2) hrs. After treatment with a solvent, (I) can be treated with an acid esp. a mixt. of organic and mineral acids, and then washed again with an aq. (II) soln.