GB1288031A - - Google Patents

Abstract

1288031 Luminescent materials JOHNSON MATTHEY & CO Ltd 5 Sept 1969 [7 June 1968] 27155/68 Heading C4S A method of making a phosphor containing yttria, at least one lanthamide oxide (e.g. La, Sn, Gd, Tb, Dy, Ho, Er, Tm, Lu) and germanium and/or gallium oxide, comprises dissolving an appropriate mixture as defined of yttria and one or more lanthanide oxides in an acid (HCl and/or HNO 3 ) to produce a solution of the salts, adding germanium and/or gallium oxide and forming a corresponding solid mixture of same, e.g. by precipitation or evaporation to dryness and converting to an oxide mixture. An appropriate mixture is defined as such that when treated the lanthanide oxide in the phosphor is in the range 0À01 to 15 atomic per cent, preferably 0À5 to 5 atomic per cent. The germanium and or gallium oxide may alternatively be added after precipitation and drying. The solid mixture may be converted by calcining, the precipitate formed by using a reagent e.g. complexing agent E.D.T.A., or ammonia solution e.g. ammonium oxalate solution or saturated oxalic acid solution, and may be separated by filtration, washed with dilute ammonia solution and dried prior to calcining. Excess ammonium hydroxide may effect precipitation or the solution may be diluted with warm distilled water and warm saturated oxalic acid or ammonium oxalite solution added to precipitate. A method of making a phosphor comprising yttrium vanadate, at least one lanthanide oxide and germanium and/or gallium oxide comprises dissolving an appropriate mixture of yttria and one or more lanthanide oxide in an acid to produce a salt solution, forming a solid mixture e.g. by precipitation or evaporation to dryness, adding vanadium pentoxide or a vanadium compound capable of yielding vanadium pentoxide when pyrolysed (e.g. ammonium metavanadate) together with germanium and/or gallium oxide, and calcining.