EUROPIUM ACTIVATED PHOSPHOR BASED ON YTTRIUM ORTHOVANADATE

1,150,833. Luminescent materials. HITACHI Ltd. 25 April, 1967 [25 April, 1966], No. 19055/67. Heading C4S. A europium activated yttrium vanadate phosphor contains 0À05 to 0À5% by wt. of Si, for instance 0À08 to 0À47 or preferably 0À17 to 0À39% by wt. The Si may be added during raw material refining processes or immediately prior to firing, suitable Si introducing materials including water glass, alkali metal silicates (such as sodium and lithium silicates), silicon dioxide, metallic silicon, silicon oxide hydrate or organo silicon compounds such as tetraethoxy-silane convertible on heating to silicon dioxides or silicates. Described are methods for introducing 0À05, 0À1, 0À2, 0À28 and 0À5% by wt. Si including adding a solution obtained by heating ammonium metavanadate with ammonia water to a solution in nitric acid of yttrium and europium oxide, adding the precipitate to an aqueous solution of vanadium pentoxide and sodium carbonate, mixing with water glass containing silicon oxide, and firing the precipitate at 1250‹ C. for 2 hours in quartz or alumina crucibles. Silicon dioxide produced by heating ethyl-silicate and -alcohol may replace the water glass. A mix of yttrium and europium oxide with vanadium pentoxide is fired for 1 hour, sodium pyrovanadate and silicon dioxide added and fired; or yttrium europium oxalate and ammonium metavanadate are fired in O 2 for 1 hr. at 800‹ C., sodium carbonate, vanadium pentoxide and silicon dioxide added and the mix fired. Uses instanced include colour T.V., highpressure Hg and plant nurturing lamps.