Up-conversion luminescent properties of CaGdAl3O7: Er3+, Yb3+, Lu3+ as a ratio optical thermometer

Abstract

Rare earth doped up-conversion luminescent materials have been extensively studied for ratio optical thermometry. Compared with commonly used fluorides, oxides have low up-conversion luminous efficiencies but good thermal stability and are more suitable for high temperature environments. In this paper, a series of CaGdAl3O7: x% Er3+, y% Yb3+, z% Lu3+ phosphors were successfully prepared by high temperature solid-state reaction. Upon 980 nm laser excitation, the optimal CaGdAl3O7: 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows bright characteristic emission peaks of Er3+. CaGdAl3O7: 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows good temperature sensing performance from 303 K to 503 K. The absolute sensitivity reaches the maximum value at 428 K (Sa = 0.292 % K−1). The maximum relative sensitivity is 0.917 % K−1 at 303 K. Moreover, CaGdAl3O7: 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows superior repeatability and reversibility. The results suggest that it is potential candidates as temperature sensors.