Frequency upconversion based thermally stable molybdate phosphors in a temperature sensing probe
Abstract
Er3+–Yb3+ co-doped NaGd(MoO4)2 phosphors with different concentrations of Er3+ and Yb3+ ions have been successfully synthesized via a high-temperature solid-state reaction method. Phase confirmation and morphological studies have been done with the help of XRD and FESEM, respectively. The suitability of being a good host material with a high refractive index has been confirmed by the diffuse reflectance study. Intense green upconversion (UC) emission has been witnessed even with the naked-eye under a relatively low pump power of a 980 nm CW diode laser excitation source. Good thermometric properties such as absolute sensitivity up to 0.053 K−1 and relative sensitivity up to 0.014 K−1 with temperature resolution of ∼0.37 K have been attained with the Stark sublevels of the thermally coupled transitions (i.e., 2H11/2, 4S3/2 → 4I15/2 level) of Er3+ ions. The reliability test of the temperature sensing ability and excellent thermal stability further confirm that the prepared phosphor can act as a worthy temperature probe.