Differences in structural and luminescent properties of GdVO4:Sm3+, Bi3+ powder and sol-gel derived films with varying Sm3+ contents and annealing temperatures

Abstract

The differences in structural and luminescent properties between powders and sol-gel particles obtained from gadolinium vanadate GdVO₄ co-doped with Sm³⁺ (0, 1, 3, 5 and 7 at. %) and Bi³⁺ (3 at. %) as a function of chemical composition and annealing temperature are presented. The ceramic was synthesised using ammonium metavanadate and gadolinium nitrate as metallic precursors, ethanol and water as solvents, citric acid as a pH modifier, acetylacetone as a chelating agent, and F-127 as a crosslinking agent. The resulting transparent films exhibit a preferential growth along the <220> direction. Moreover, there is an energy transfer mechanism from Bi³⁺ to Sm³⁺ (via electric dipole-electric dipole interactions),and depending on the content of Sm³⁺ and Bi³⁺, it is possible to tune the luminescent colour response, obtaining blue, pink, white, and red emission. We also observed that the Bi³⁺ emission band presents a blue shift from 520 nm in powders to 510 nm in films, which also causes a red shift in the co-doped samples. This shift modifies the CIE (Commission Internationale de l' Eclairage) coordinates of the films compared with powders, where the powders emit colours in the yellow region of the spectrum, and the films shift towards the white region of the spectrum.