Optical Temperature Sensing Behavior of High-Efficiency Upconversion: Er3+-Yb3+ Co-Doped NaY(MoO4)2 Phosphor

A class of Yb3+/Er3+ co-doped NaY(MoO4)(2) upconversion (UC) phosphors have been successfully synthesized by a facile hydrothermal route with further calcination. The structural properties and the phase composition of the samples were characterized by X-ray diffraction (XRD). The UC luminescence properties of Yb3+/Er3+ co-doped NaY(MoO4)(2) were investigated in detail. Concentration-dependent studies revealed that the optimal composition was realized for a 2% Er3+ and 10% Yb3+-doping concentration. Two-photon excitation UC mechanism further illustrated that the green enhancement arised from a novel energy-transfer (ET) pathway which entailed a strong ground-state absorption of Yb3+ ions and the excited state absorption of Yb3+-MoO42- dimers, followed by an effective energy transfer to the high-energy state of Er3+ ions. We have also studied the thermal properties of UC emissions between 303 and 523K for the optical thermometry behavior under a 980nm laser diode excitation for the first time. The higher sensitivity for temperature measurement could be obtained compared to the previous reported rare-earth ions fluorescence based optical temperature sensors. These results indicated that the present sample was a promising candidate for optical temperature sensors with high sensitivity.