Optical Temperature Sensing Behavior of High‐Efficiency Upconversion: Er ³⁺ –Yb ³⁺ Co‐Doped NaY(MoO ₄ ) ₂ Phosphor

Abstract

A class of Yb 3+ /Er 3+ co‐doped NaY(MoO 4 ) 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 Yb 3+ /Er 3+ co‐doped NaY(MoO 4 ) 2 were investigated in detail. Concentration‐dependent studies revealed that the optimal composition was realized for a 2% Er 3+ and 10% Yb 3+ ‐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 Yb 3+ ions and the excited state absorption of Yb 3+ –MoO 4 2− dimers, followed by an effective energy transfer to the high‐energy state of Er 3+ ions. We have also studied the thermal properties of UC emissions between 303 and 523 K for the optical thermometry behavior under a 980 nm 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.