Metal tungstate for prodn. of lead perovskite electro-ceramics and X=ray improving luminescent materials

摘要

A phase-free, crystalline metal tungstate of general formula Me(II)WO4, in which Me(II) = Co, Ni, Zn, Pb, Mg, Ca, Sr or Ba is novel in that it has a grain distribution of d 90% < 5 mu m, d 50% < 1 mu m and d 10% < 0.3 mu m. Also claimed is a process for producing the above metal tungstates by wet mixing of the corresponding metal cpds. and tungsten components, drying and opt. calcining. The process is novel in that the tungsten component is added in the form of ammonium para-tungstate and/or ammonium meta-tungstate. The tungstate pref. has a specific surface area of 2.5-30 m<2>/g. The wet mixing is performed for 5-90 mins.. The drying and calcining is carried out at 100-1200 deg C.