Synthesis and Electron Dependent Properties of the Phosphor Gd2O2S:Ce3+, Tb3+

A substitutional solid solution of (Gd_0.94Ce_0.03Tb_0.03)₂O₃ (Ia$$, a = 10.8496 (5) Å, V = 1277.1 (2) Å³) was obtained by hydrothermal synthesis from rare earth nitrates and sodium hydroxide, followed by calcination in air at 900 °C for 2 h. The subsequent sulfidation of the compound in a hydrogen sulfide stream at 900 °C for 9 h yielded a substitutional solid solution of the oxysulfide (Gd_0.94Ce_0.03Tb_0.03)₂O₂S (P$$m1, a = 3.8682 (4) Å, c = 6.6770 (8) Å, V = 86.52 (2) Å³). A qualitative and quantitative analysis of the obtained samples was carried out using the Rietveld method, along with morphological characterization of the particles. A mechanism for the transformation of particles at different stages of synthesis has been proposed. Combined experimental and theoretical investigations showed possibility of both direct and indirect electronic transitions in (Gd_0.94Ce_0.03Tb_0.03)₂O₂S. Density functional theory calculations highlighted the complex nature of charge transfer in lanthanide oxysulfides, suggesting further investigations. The results of the study on the photoluminescent properties of the obtained phosphors showed that Tb³⁺ ions play a major role in the emission processes, with the most intense emission band occurring in the green spectral region at 538 nm. In addition to the narrow terbium bands, weak cerium emission was also observed, covering a broad spectral range of 350–700 nm.