Luminescent lanthanum gallate activated by trivalent thulium, luminescent screen provided with such a gallate and cathode ray tube provided with such a screen

摘要

Luminescent lanthanum gallate having the perovs­kite structure and activated by trivalent Tm. The gallate comprises aluminium and is defined by the formula La1-xTmxGa1-yAlyO₃ in which up to 20 mol.% of the lanthanum may be replaced by yttrium, gadolinium, lutetium and/or scandium and in which 10⁻⁴ ≦ x ≦ 0.05 and 0.20 ≦ y ≦ 0.80. Upon cathode ray excitation the gallate has the narrow blue-line emission of Tm³⁺ and is parti­cularly suitable for use in the luminescent screen of high-load cathode ray tubes, for example projection television tubes.