| 摘要 |
<p>1,243,326. Recrystallizing oxysulphides. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 19 March. 1970 [22 March, 1969], No. 13322/70. Heading C1A. [Also in Division C4] A method of recrystallizing an oxysulphide of one or more elements having atomic numbers 57 to 71 inclusive and 39, comprising preparing a mixture of the oxysulphide together with a sulphide and/or polysulphide of one or more of the alkali metals or with substances which when heated produce a sulphide and/or polysulphide of an alkali metal, heating to 1000‹ to 1500‹ C. preferably in a gas-tight space for 0.25 to 15 hours and cooling. A luminescent oxysulphide may be of formula A (2-x) B x O 2 S where A is one or more of Y, Gd, La and Lu, B is element of atomic number 58 to 71 and x is 0.0002 to 0.2. The activator may be trivalent Eu or Tb giving red and green emission with colour TV tube and in the latter case also X-ray image intensifier tubes. Alkali metal thiosulphates (e.g. of Na and/or K) may be used preferably in amount 0.2 to 20 moles per mole of oxysulphide reducing to sulphides or polysulphides on heating. The basic material may be mixed with sulphur and an alkali metal compound, e.g. one or more hydroxide, carbonate or sulphite, 0.05 to 5 moles of sulphide and/or polysulphide or equivalent being preferred. The recrystallization produces enlarged crystals which may have enhanced luminescence, may be better provided on a screen and more resistant to photochemical binder attack. Recrystallizations described of Y 1À9 Eu 0À1 O 2 S produce 2Á crystals, the oxysulphide being first produced by heating sodium thiocyanates with the oxides and being of a brightness in a demountable c.r.t., 3% that of the recrystallized product. Other recrystallizations specified are Y 1À92 Eu 0À08 O 2 S and Na 2 S heated in N 2 ; La 2 O 2 S with Eu 2 O 2 S and Na 2 S 4 heated in a closed crucible; Y 1À9 Eu 0À1 O 2 S with NaOH and S heated in a closed crucible; and Gd 1À98 Tb 0À02 O 2 S with Na 2 C0 3 and S in a closed crucible, the final products being water leached and dried. Non-luminescent products may be analogously recrystallized.</p> |
