Optimizing the thermal stability of Tb3+-based phosphor through intervalence charge transfer compensation and charge transfer band edge red-shift

Abstract

Thermal quenching (TQ) limits the large-scale practical application of most luminescent materials, so the investigation on thermal quenching phenomenon of phosphors has emerged as a prominent research area, garnering significant attention in academic circles. The thermal quenching performance is closely related to the charge transfer band (CTB) and intervalence charge transfer (IVCT) band. Herein, we study the correlation between CTB edge red-shift, IVCT band position and the thermal stability of Tb3+-based lithium tantalate phosphors, aiming to regulate the thermal quenching performance. The results show that totally anomalous thermal quenching (TATQ) was found to exist in LiTaO3:xTb3+ phosphors during the process of temperature rising, and the whole CTB edge absorption showed a red-shift and enhance with increasing temperature. Based on this characteristic phenomenon, under the excitation of CTB edge (270 nm), the phosphor exhibits obvious antithermal quenching. In addition, the existence of the Tb3+-Ta5+ IVCT band can be used as a compensation channel for Tb3+ 5D3 → 5D4 transition, which makes the phosphor produce stronger antithermal quenching performance. Accordingly, the co-regulation of the CTB edge red-shift and IVCT compensation effect was proposed. Modulation of Tb3+ concentration revealed that during thermal activation (λem = 547 nm), LiTaO3:0.005Tb3+ luminescence integral intensity (423 K) reaches 255.6% of the initial intensity, phosphor achieves the most excellent performance. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) for temperature sensing scheme based on the intensity ratio of excitation spectrum CTB and CTB-IVCT reaches 0.996%@523 K and 0.927%@523 K, respectively. The co-regulation strategy of thermal activation-induced CTB edge red-shift and IVCT compensation channel provides a promising research idea for developing Tb3+-based antithermal quenching luminescent materials.