Near-infrared to visible up-conversion in Er3+ doped LaAlO3 phosphors and their assessment as an optical temperature sensor

Abstract

The present work studies the optical temperature sensing in micro and nanospheres of LaAlO3, synthesized by a Pechini sol-gel method. The optical properties focus on the up-conversion emission and optical temperature sensing properties of thermally and non-thermally coupled levels. Exciting at 975 nm, the up-conversion produces three emissions bands centered at 533, 545, and 670 nm. When the concentration of Er ion increases, the intensity of emission increases up to 5 %. The mechanism shows the absorption of two photons and the energy transfer up-conversion process. Optical temperature sensing is studied in the range of 299–327 K based on thermal coupled and non-thermal coupled levels by the luminescence intensity ratio technique. The absolute sensitivity, relative sensitivity, and uncertainty temperature values were obtained to study the material's performance and applicability. The maximum absolute and relative sensitivity values are 5.21 × 10−3 K−1 at 327 K for I670/I545 and 0.87 % at 299 K for I533/545. On the other hand, the temperature uncertainty is 0.2 K, indicating that the present material may be used as an effective temperature-sensing device using thermal coupled and non-thermal coupled levels.