Photoluminescence of Gd<inf>2</inf>O<inf>3</inf> and Gd<inf>2</inf>O<inf>3</inf>:Ln³⁺ (Ln = Eu, Er, Ho) formed by plasma electrolytic oxidation of pure gadolinium substrate

Abstract

Gd2O3 and Gd2O3:Ln3+ (Ln = Eu, Er, Ho) coatings were formed by the fast and cheap plasma electrolytic oxidation (PEO) process, from the pure gadolinium plate and an addition of appropriate Ln2O3 particles to the supporting electrolyte. Monoclinic phase of Gd2O3 is identified in all samples. Gd2O3 absorbs in the UV region and the photoluminescence in the visible region is attributed to the two-photon absorption process and a non-radiative relaxation to the emitting 6GJ multiplet. In Gd2O3:Ln3+, the spectra reveal an efficient energy transfer to the Ln3+, and observed photoluminescence is a combination of Gd3+ and Ln3+ 4f-f4 transitions. CIE chromaticity diagram of all samples excited at various wavelengths has been estimated, with emissions ranging in the area from green to white to orange.