Optical temperature sensing via FIR technology of Sm3+ doped KNN-based translucent ceramics

Rare-earth ions (Re³⁺) with up-conversion luminescence properties doped in materials have regarded as novel optical materials due to temperature sensing and photochromic effect, which have widely researched. However, the energy loss caused by photochromic reaction and thermal quenching obstacle the practical applications. Herein, x mol% Sm₂O₃ doped KNN-based ceramics 0.94 K_0.5Na_0.5NbO₃-0.06Sr_0.5Ca_0.5NbO₃ ceramics (x = 0.05, 0.15, 0.25, 0.35, abbreviated as KNN-SCN: xSm) with high transmittance and photoluminescence were prepared successfully by traditional high temperature sintering reaction method, which realized temperature sensing by fluorescence intensity ratio (FIR) technology. High transmittance (T) was resulted from high symmetrical structure and small grains and the transmittance was obtained in KNN-SCN: 0.15Sm ceramic which up to 55.95 % in the visible light area and 67.37 % in the near infrared range (1100 nm). Meanwhile, optical temperature sensing was measured at 298–473 K and the maximum absolution sensitivity (S_a) and relative sensitivity (S_r) were achieved 0.0223 K⁻¹ (at 298 K) and 0.0610 K⁻¹ (at 298 K) respectively. Although the sensitivity decreasing with temperature increasing, the S_a and S_r were achieved 0.0132 K⁻¹ and 0.0242 K⁻¹ at 473 K respectively which still contain higher sensitivity than other optical temperature sensors.