Dualistic temperature sensing in Er3+/Yb3+ doped CaMoO4 upconversion phosphor

Temperature sensing performance of Er3+/Yb3+ doped CaMoO4 phosphor prepared via polyol method is reported herein. The X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy are done to confirm the phase, structure and purity of the synthesized phosphor. The infrared to green upconversion emission is investigated using 980 nm diode laser excitation along with its dependence on input pump power and external temperature. The temperature dependent fluorescence intensity ratio of two upconversion emission bands assigned to H-2(11/2) -> I-4(15/2) (530 nm) and S-4(3/2) -> I-4(15/2) (552 nm) transitions has shown two distinct slopes in the studied temperature range - 300 to 760 I< and therefore, dual nature of temperature sensitivity is observed in this phosphor. This phenomenon in rare earth doped materials is either scarcely reported or overlooked. The material has shown higher sensitivity in the high temperature region (535 K < T< 760 K) with a maximum of 721 x 10(-3) K-1 at 535 K. The results indicate potential of CaMoO4: Er3+/Yb3+ phosphor in high temperature thermometry. (C) 2016 Elsevier B.V. All rights reserved.