Enhanced photoluminescence and thermal stability in solid solution Ca1−xSrxSc2O4:Ce3+ (x = 0–1) via crystal field regulation and site-preferential occupation

Abstract

A series of cyan-to-green emission tunable Ce³⁺-activated Ca_1−xSr_xSc₂O₄ phosphor compounds were developed through a high-temperature solid-state reaction. The crystal structures were analyzed by XRD and the Rietveld refinement, which confirm the phase purity and clarify the structural variation. The photoluminescence properties and thermal stabilities of the studied phosphors were investigated in detail. The diffuse reflectance spectra revealed the optical band gap to be 4.60 eV and 4.45 eV for CaSc₂O₄ and SrSc₂O₄ host, respectively. Due to the suitable optical bandgap, the Ce³⁺ ions could realize a highly efficient emission in the Ca_1−xSr_xSc₂O₄ matrix. The as-prepared phosphors show highly efficient emissions in the green to cyan regions of visible light. All developed compounds demonstrate asymmetric broad-bands with shoulders on the lower-energy sides. Cation substitution-dependent color-tunable evolution as a function of Sr²⁺ content in Ce³⁺-doped Ca_1−xSr_xSc₂O₄ was observed and investigated in detail. The regular blue-shift emission located in the cyan region with increasing Sr²⁺ content was attributed to the combined effect of the crystal field splitting and site-preferential occupation. The corresponding luminescence mechanism was analyzed through luminescence life decay measurements. Moreover, the increase of Sr²⁺ content could efficiently enhance the emission intensity and decrease thermal quenching, which should be ascribed to the lattice modification. The bright cyan and green emission band in the developed compounds, due to transitions in the 5d–4f levels of Ce³⁺, was found to be ideal for application in solid-state lighting devices. The feasibility of the compound as a potential white LED phosphor was demonstrated by fabricating a white LED with excellent emission properties.