Cathodoluminescence characteristics of bismuth-doped lanthanide niobates

Abstract

The study is devoted to the study of lanthanide niobates activated by bismuth, interesting in connection with the use of these materials in the production of phosphors used in various fields of human activity, medicine, industry, science. The purpose of the study is to study the luminescent characteristics of phosphors suitable for use in solid-state light sources and field emission displays. At present, the most thoroughly studied lanthanide niobates are lutetium, yttrium and gadolinium activated by various trivalent rare-earth ions (Eu³⁺, Tb³⁺, Dy³⁺). Much less studied are niobates activated only by Bi³⁺ ions or simultaneously by both Bi³⁺ ions and rare-earth ions. In the presented study, microcrystalline powders of yttrium, lutetium and gadolinium niobates doped with trivalent bismuth were studied by cathodoluminescence spectroscopy in a wide temperature range. The study was carried out under excitation by an electron beam with an energy of about 100 keV, having a penetration depth of more than 20 μm to reduce the influence of surface effects on luminescence. For the samples of (Y, Lu, Gd) NbO4: Bi, as well as nominally pure LuNbO₄, the cathodoluminescence spectra were measured, both integral and with time resolution. A comparison with the photoluminescence characteristics of these samples was carried out. An assumption was made that intense wide bands of cathodoluminescence have a complex structure and are a superposition of several bands of exciton nature. The presence of weak ultrafast radiation in the ultraviolet region of the spectrum related to the so-called intraband luminescence was noted. The obtained data are of both scientific and practical interest in the further development of functional materials.