Photoluminescence study of (CaO)1 –x(ZnO)x powder solids in air

Abstract

Luminescence from (CaO)_{1 minus; x}(x= 0–1) powder solids, prepared by thermal treatment in air at 1423 K, was observed at room temperature by means of high-energy UV excitation (5.2–6.2 eV). In general, broad emission bands centred in the visible region of the spectrum were recorded, with features dependent upon the excitation wavelength as well as on the sample nature. The presence of small quantities of winc within the CaO results in a dramatic enhancement of the photoluminescence intensity, reaching a maximum at 1% addition of Zn atoms/Ca + Zn atoms. In this case, a nearly twenty-fold increment in photoluminescence intensity was observed. The emission band showed a peak at 435 nm (2.85 eV) and was excited to a maximum by 210 nm (5.9 eV) light. Photoinduced electron transfer, followed by recombination processes involving oxygen anion vacancies as well as photogenerated F⁺ and F centres, are possibly the cause of the observed lumniscence.