Ultra-high sensitivity of multicolor Sm³⁺-doped LiSrVO₄ phosphors for contactless optical thermometers

To overcome the existing challenge of temperature monitoring with high accuracy, we designed Sm³⁺-doped LiSrVO₄ phosphors with ultra-high sensitivity as promising candidates for optical thermometers. The prepared samples could emit multicolor emissions after excitation at 343 nm and the optimum doping concentration for the Sm³⁺ ions in the selected host was 1 mol%. The mechanism of energy transfer from the VO₄^3- group to the Sm³⁺ ions was studied and its efficiency was proved to be 84.1% for an Sm³⁺ ion content of 7 mol%. Based on the disparate thermal quenching performances of the VO₄^3- group and Sm³⁺ ions, the temperature monitoring ability of the prepared compounds was examined. Through choosing different emissions of Sm³⁺ ions, and then combining them with the VO₄^3- group, optical thermometers with controllable sensitivity were realized. The maximum absolute and relative sensitivities of the resultant phosphors could reach ultra-high values of 1.076 K^-1 and 6.167% K^-1, respectively, which were the highest sensitivities reported so far. Furthermore, the doping content also impacted the sensitivities of the resultant compounds.