Multimode optical thermometry using CaWO4 emission band

Optical thermometry has emerged as a promising technique for remote temperature sensing in plenty of applications, where traditional contact methods are useless. To date, many sensing strategies have been developed and realized, but most of them are based on monitoring of the single temperature dependent parameter. Here, we report simple dual-center materials (Eu ³⁺ and Sm ³⁺-doped CaWO ₄) that provide multimode optical thermometry. In addition to standard ratiometric approach based on intensity ratio between host and lanthanide emission bands, spectral position and bandwidth of CaWO ₄ emission band were successfully utilized as temperature sensitive parameters for the first time. It was shown that multimode sensing leads to broadening of temperature working range and enhances reliability of thermal sensing. The best thermometric characteristics were achieved for CaWO ₄:Sm ³⁺ sample: S _r = 1.29 % K ⁻¹@273–673 K and δT = 0.15 K.