Ca9KLa(2/3)(VO4)7:Sm3+における格子工学を介した負の熱失活による高感度温度センシング

The persistent issue of thermal quenching in phosphors has significantly limited their high-temperature applications. To address this, we designed a novel phosphor, Ca₉KLa_2/3(VO₄)₇:Sm³⁺ (CKLV:xSm³⁺), which exhibits dual thermal quenching (TQ) behavior through a defect engineering strategy. Specifically, the matrix (VO₄^3-) shows thermal quenching (TQ), while the activator Sm³⁺ exhibits negative thermal quenching (NTQ). This phenomenon stems from the synergistic effect of the phonon-assisted energy transfer from VO₄^3- to Sm³⁺ and thermally-induced energy transfer between defect levels and the excited states of Sm³⁺. The contrasting thermal quenching behaviors of Sm³⁺ and VO₄^3- form the basis for self-referenced optical thermometry, and CKLV:xSm³⁺ shows thermal sensing sensitivity with maximum Sₐ and Sᵣ values of 0.078 K^-1 (at 475 K) and 1.19% K^-1 (at 350 K), respectively. To further improve their performance, lattice engineering was employed to augment the lattice distortion and enhance the luminescence of the VO₄^3- group. This approach proved highly effective, and the optimized Ca₈MgKLa_2/3(VO₄)₇:Sm³⁺ sample achieved a Sᵣ-max of 2.01% K^-1, increased by 69% over the undoped system. Additionally, the material exhibits distinct thermochromism, with a green-to-red emission shift upon heating, enabling visual temperature displaying and high-temperature alarm functionality. These findings validate its strong potential as a high-performance luminescent thermometer for advanced sensing applications.