| 摘要 |
1,134,530. Luminescent materials and processing. GENERAL ELECTRIC CO. 3 March, 1967 [2 May, 1966], No. 10202/67. Heading C4S. A process for producing improved luminescent materials of yttrium vanadate activated with europium comprises the steps of (a) recrystallizing the YV0 4 : Eu in a molten salt bath which bath comprises major portions of V 2 0 5 and then mixing sufficient quantities of water and oxalic acid to dissolve substantial quantities of the V 2 O 5 present, thus changing the predominant appearance of the material from that of a reddish-brown suspension to a blue solution containing suspended phosphor particles, (b) adding sufficient quantities of basic compounds such as NaOH, Na 2 CO 3 or NH 4 OH to raise the pH to 7 or above, (c) followed by the addition of an oxidizing agent such as H 2 O 2 to produce a clear colourless or light yellow solution and (d) separating the phosphor crystals from the solution. Preferably for each 100 parts by wt. of V 2 O 5 in the recrystallization bath, 5 to 300 parts by wt. of oxalic acid in water is used, allowed to digest the V 2 O 5 for about 30 mins. at 80‹ to 90‹ C., a 50% NaOH solution and hydrogen -peroxide added slowly in turn, the suspension digested for 20 mins., filtered, washed and dried in air at 120‹ C. Uses include colour television tubes, mercury discharge lamps and lasers. Particles of medium diameter 9-4 4 microns-and 2% by wt. over 15 microns may be produced. |
