Crystalline lanthanum-oxy-halide phosphor activated with rare earths

US4793944A · kind A · utility

Assignee

• VEB Mikroelektronik, Leuchtstoffwerk Bad Liebenstein · DE

Inventors

• Gerhard Herzog · Greifswald, DE
• Detlef Starick · Berlin, DE
• Walter Tews · Greifswald, DE
• Franz Braunholz · Bad Liebenstein, DE
• Aleksander M. Gurvic · Moskovskiy, RU
• Svetlana I. Golovkova · Khimki, RU
• Karl Dietzel · Bad Liebenstein, DE

Key dates

• Filing date: Sep 30, 1987
• Grant date: Dec 27, 1988
• Expiry date: Sep 30, 2007

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09K11/777
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

The invention concerns a crystalline lanthanum-oxy-halide phosphor activated with rare earths which emits light in the ultraviolet and blue spectral range by high-energy excitation, particularly X-ray excitation. Such phosphors are used, for instance, in X-ray image converters, particularly in X-ray amplifying screens. It is the object and purpose of the invention to state a new oxy-halide phosphor with changed composition which ensures a high image quality of corresponding amplifying screens and at sufficiently little phosphorescence renders an optimal conversion of the X-rays to the photographically effectual luminescence possible. This is achieved by simultaneous use of thulium and gadolinium as activators where the phosphor represents the general formula La.sub.1-y-z OX:Tm.sub.y.sup.3+, in which X=Cl and/or Br and y represents values from 0.0001 to 0.1 preferably from 0.0005 to 0.005 as well as z represents values from 0.001 to 0.3 preferably from 0.002 to 0.05. These phosphors can be manufactured in a simple manner, for instance, by converting a mixed oxide of lanthanum, thulium and gadolinium with a suitable ammonium halide, followed by a recrystallization of the resulting ma…