Frequency upconversion based thermally stable molybdate phosphors in a temperature sensing probe

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 similar to 0.37 K have been attained with the Stark sublevels of the thermally coupled transitions (i.e., H-2(11/2), S-4(3/2) -> I-4(15/2) 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.