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 ⁴G_5/2 (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.