Optical properties of Sm³⁺ and Tb³⁺ co-doped CaMoO₄ phosphor for temperature sensing

We prepared CaMoO₄: x%Sm³⁺, 5%Tb³⁺ (x = 0.1, 0.5, 1, 2) phosphors by a precipitation method. Based on the diversity in thermal quenching behavior of different ions in molybdate, a novel thermometry strategy has been proposed. The fluorescence intensity ratio (FIR) of Sm³⁺ to Tb³⁺ in these composites exhibits remarkable temperature dependence due to the diverse thermal quenching behaviors of Sm³⁺ and Tb³⁺ ions. Excellent temperature sensitivity was achieved from 293 K to 593 K, suggesting that these can perform thermometry. The sensitivities increase with Sm³⁺ concentration. The maximum sensitivity is as high as 0.312 K^-1 (at 593 K) when the Sm³⁺ concentration is 2%. However, the low Sm³⁺ concentration sample has a greater relative sensitivity; the maximum value is as high as 0.019 K^-1 (at 460 K) when the Sm³⁺ concentration is 0.1%. Lower Sm³⁺ concentrations suggested a greater range of luminescent color changes with temperature. Thus, the sample with less Sm³⁺ can measure temperature via luminescent color.