Optical temperature sensing in LaInO3:Er3+ by up-conversion emission exciting at 975 nm

This work reports the luminescent properties of Er³⁺ ion-doped LaInO₃ for temperature detection and measurement. The samples were synthesized using the Pechini sol-gel method, obtaining pure, homogeneous materials with non-defined morphology that agglomerate forming microspheres. Exciting at 975 nm, up-conversion was obtained with emission bands centered at 527, 542 and 675 nm, which are generated due to the absorption of two photons and an energy transfer mechanism. The ratio between 527 and 542 nm emissions, well known thermally coupled levels, was studied as a function of temperature in the range between 297 and 327 K using the luminescence intensity ratio technique. The thermometric parameters of absolute sensitivity, relative sensitivity, and uncertainty were obtained to evaluate the material's application in luminescent thermometry. The maximum sensitivity and relative sensitivity values found were 6.18 x 10⁻³ % K⁻¹ at 417 K and 1.05 % K⁻¹ at 297 K, while the uncertainty found was 0.07 K at 297 K and 0.15 K at 417 K. The uncertainty values are excellent due to the intense emission of the samples, leading to a very high signal/noise ratio.