method for preparation of crystals of oxydechloriden and / or oxydebromiden of at least one of the elements in the atoomnummers 39 and 57 to 71.

摘要

1279426 Rare earth oxyhalides and oxides GENERAL ELECTRIC CO 9 Oct 1969 [23 Oct 1968] 49644/69 Heading C1A [Also in Division C4] Rare earth metal (including yttrium) oxychloride and oxybromide crystals are prepared by heating at 400-500‹ C. a mixture of r.e. oxide and NH 4 halide to form poorly crystalline oxyhalide then reheating at 800-1200‹ C. with an alkali metal halide to recrystallise the oxyhalide, alkali metal carbonate may be added to the initial mixture to react with the NH 4 halide to form the alkali metal halide in situ during the first heating step. The oxyhalide may be converted to oxide by heating at 800-1100‹ C. in flowing CO 2 . The materials may be luminescent and activated by Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er and Tm. The preparation of YOCl:Eu, LaOCl-Br:Tb and GdOCl:Eu is described using Na, K and Li salts. Particles of 3-50 micron diameter are prepared for use in C.R.T.s X-ray converter tubes and fluoroscopic screens.