Tuning of the thermal quenching performance of Bi³⁺-doped scheelite Ca(Mo/W)O₄ solid solution phosphors

The utilization of phosphor materials has always been a significant challenge in terms of improving thermal quenching performance. In this work, the thermal quenching performance tuning mechanism which establishes the band gap and thermal quenching correlation patterns is proposed. The crystal field splitting energy D_q was decreased by changing the surrounding crystal lattice environment of Bi³⁺ through a solid solution replacement, and the thermal quenching activation energy ΔE of Bi³⁺ was tuned from 0.117 eV to 0.182 eV accordingly. At 423 K, the luminous intensity increases from 0.101 to 0.396 of the preliminary intensity at 303 K with increasing substitution. In addition, the band gap value of Bi³⁺ calculated by diffuse reflectance spectroscopy increased from 4.40 eV to 4.72 eV, which corresponds to a linear positive correlation between the band gap and the thermal quenching properties. Furthermore, a monophase white-emitting phosphor with good thermal stability was prepared by constructing a Bi³⁺-Eu³⁺ co-doping system. In particular, the relative sensitivity of S_r for temperature measurement applications reached 3.17% K^-1 based on the double-luminescence fluorescence intensity ratio. Thus, this modulation scheme can be used as a reference for the design of various phosphor materials with tunable thermal quenching properties in the future.