1,133,811. Luminescent materials and processing. GENERAL ELECTRIC CO. 22 March, 1967 [2 May, 1966], No. 13352/67. Heading C4S. A. process for producing crystalline yttrium vanadate activated with europium includes providing a batch of the constituents for the production of the desired stoichiometric mposition and bath producing materials; heating said batch to melt said bath-producing materials and to cause recrystallization of the constituent phosphor materials and maintaining at the temperature for a time sufficient to produce crystals of the desired size; then cooling to solidify the bath producing materials, the bath producing materials being in amount at least 5 weight per cent (preferably 5 to 50) relative to the YVO 4 : Eu, and consisting of LiVO 3 , LiVO 3 plus V 2 O 5 or materials which decompose or react to produce LiVO 3 or V 2 O 5 , the proportions of LiVO 3 to V 2 O 5 or materials which decompose or react to produce LiVO 3 or V 2 O 5 calculated in the form of LiVO 3 and V 2 O 5 , being from 5 to 100 (preferably 5 to 50) weight per cent LiVO 3 , the balance, if any, V 2 O 5 . The phosphor may be used in colour T.V. tubes, mercury lamps and lasers. A preferred composition is (Y 0 . 95 Eu 0 . 05 )VO 4 .