Low-voltage cathodoluminescence of europium-activated yttrium orthovanadate

摘要

Emissive flat panel display systems operating in full color demand higher performance at low voltages (ca. 501000 V) from cathodoluminescent (CL) phosphors than cathode ray tubes require. Hydrothermal synthesis has been suggested as a route to phosphors with improved efficiencies, lower voltage thresholds, and increased saturation power. This hypothesis was tested in europium-doped yttrium orthovanadate (YVO(sub 4):Eu), an efficient, red emitting CL phosphor. The CL efficiency of YVO(sub 4):Eu crystallized from aqueous solution at 200(degrees)C is relatively low until it is annealed. The distribution of particle sizes in the low-temperature phosphor is similar to that in material made via a solid-state route, but crystallites remain much smaller (ca. 400 (Angstrom)) until they are annealed. These observations, along with the anomalously strong dependence of CL intensity on europium concentration, support a model in which efficiency principally depends on crystallite size. CL efficiency of both solid state and hydrothermal YVO(sub 4):Eu increases with voltage at constant power. Surface-bound electrons are likely the dominant influence on efficiency at voltages near threshold. Saturation power is independent of synthetic route. It is apparent that the CL properties of hydrothermally synthesized YVO(sub 4):Eu are essentially the same as those of YVO(sub 4):Eu produced via conventional, high-temperature routes.