Sensitivity Enhancement of Thermometry in Tb3+-Doped KY(CO3)2:Sm3+ by Energy Transfer

Sm3+ and Tb3+ co-doped KY(CO3)2 temperature sensing materials were prepared via the hydrothermal method. X-ray diffraction results confirmed the monoclinic phase in KY(CO3)2:Sm3+,Tb3+ samples. In this KY(CO3)2 host, Tb3+ transfers energy to Sm3+ through cross-relaxation. Notably, a 20 mol% concentration of Tb3+ increases the emission intensity of Sm3+ by 7.1 times. The fluorescence emission intensities of 5D4 (Tb3+) and 4G5/2 (Sm3+) vary significantly with temperature. Both Sm3+-Sm3+ and Tb3+-Sm3+ pairs act as effective emission centers in KY(CO3)2:Sm3+,Tb3+ for optical temperature measurement. The relationship between fluorescence intensity ratio (I542/I567) and temperature reveals that the maximum absolute sensitivity and relative sensitivity of KY(CO3)2:Sm3+,Tb3+ are 0.031 K−1 and 0.46%K−1 at room temperature of 298 K, respectively. In contrast, KY(CO3)2:Sm3+ has a maximum absolute sensitivity of only 0.00051 K−1 and a relative sensitivity of 0.11%K−1 at 498 K. These results highlight the significant role of Tb3+ in enhancing Sm3+ emission intensities, making Tb3+ doped KY(CO3)2:Sm3+ a promising candidate for thermometry.