Precise Temperature Sensing and Optical Information Storage via Dual-Emission Gallate Phosphors

Luminescent temperature sensing has become a research hotspot in the past few years. Nevertheless, improving the sensitivity and resolution remains a key challenge. Herein, Bi³⁺,Sm³⁺-codoped CaYGaO₄ phosphors with precise temperature sensing performance and excellent photochromic characteristics were developed. The energy difference between the Sm³⁺ levels hinders the multiphoton relaxation (MPR) process, giving rise to temperature insensitivity. By virtue of the drastically different temperature dependence between Bi³⁺ and Sm³⁺ ions, an accurate fluorescence intensity ratio (FIR) thermometer is fabricated. Sm³⁺ emission is used as a reference signal, while Bi³⁺ emission is adopted as a probe signal. The maximum absolute sensitivity (S_a) and relative sensitivity (S_r) of the CaYGaO₄:Bi³⁺,Sm³⁺ phosphors are 0.0018 K^-1 (@563 K) and 0.56% K^-1 (@544 K), respectively. Moreover, the CaYGaO₄:Bi³⁺,Sm³⁺ exhibits superior photochromic characteristics, rapidly changing its color from white to brown in 25 s under 254 nm light irradiation, and has outstanding cycling stability. Overall, the phosphors provide potential multifunctional applications in anticounterfeiting and optical information storage fields.