Largely enhanced luminescence intensity and improved optical temperature sensing properties in CaWO₄-La₂(WO₄)₃: Er³⁺,...

High temperature sensing sensitivity and luminescence intensity of phosphors are crucial factors for excellent optical temperature sensing performance. Based on material design, the pure phase and two-phase solid solutions were prepared by regulating the relative content of cations Ca²⁺ and La³⁺ in CaWO₄-La₂(WO₄)₃, respectively. The up-conversion luminescence (UCL) and optical temperature sensing performance of rare earth ions Er³⁺/Yb³⁺ co-doped CaWO₄-La₂(WO₄)₃ were studied. As guided by regulating cation composition through partial substituting Ca²⁺ ions by La³⁺ ions, the UCL intensity of two-phase solid solutions at 552 nm is much higher than that of pure phase material. The UCL intensity of 0.2La₂(WO₄)₃-0.8CaWO₄: 1%Er³⁺, 5%Yb³⁺ is as 33.5 times as that of CaWO₄: 1%Er³⁺, 5%Yb³⁺ material. More importantly, the high temperature sensing sensitivity (0.01026 K^-1) is achieved in a wider temperature range 83-683 K in optimal UCL material 0.2La₂(WO₄)₃-0.8CaWO₄: 1%Er³⁺, 5%Yb³⁺. It is suggested that material design theory can be used as a powerful tool to accelerate discovery of novel optical temperature sensing materials, with implications even for the design of other optoelectronic materials.