Luminescence properties and cathodoluminescence degradation of Bi doped SrO powder

Abstract

Bi3+ doped strontium oxide (SrO:Bi) phosphor powders were synthesized by the solgel combustion method using metal nitrates as precursors and citric acid as fuel. The optimum Bi3+ doping concentration was found to be 0.2 mol. %, and the optimum annealing temperature was found to be 1100 °C (2 h). The x-ray diffraction patterns corresponded with the known face-centered-cubic structure of SrO. Williamson–Hall plots showed that the crystallite size was in the range of ∼180 nm. Diffuse reflectance measurements of the pure host material showed that it was strongly reflecting (∼100%) down to a wavelength of about 230 nm, but when doped with Bi, an absorption band at 275 nm was observed that increased with Bi concentration. Scanning electron microscopy revealed a cubic morphology, and the grain size increased with annealing temperature. Photoluminescence measurements indicated that the phosphor exhibited efficient blue emission around 445 nm under UV excitation, which also occurred for electron irradiation, but slightly shifted about 5 nm to a longer wavelength. Auger electron spectroscopy (AES) was employed to analyze the surface chemical composition of the powder after pumping to a vacuum pressure of 2.6 × 10−8 Torr and back-filling the vacuum system with O2 to a pressure of 1.0 × 10−7 Torr. By simultaneous monitoring of the cathodoluminescence (CL) and AES peak-to-peak heights over time for 22 h, the CL degradation of the phosphor was investigated. SrO was found to be stable under electron irradiation. The phosphor may have potential applications in the fields of lighting and displays due to its broad blue emission.