Optically thermometric sensitivities of Er3+/Yb3+ Co-doped hosts with different phonon energy

Abstract

For Up-conversion (UC) optical thermometers based on luminescence intensity ratio (LIR) technology, the eternal pursuit is achieving high sensitivity to minimize its temperature measurement uncertainty, in which the selection strategy of matrix and dopants is one of the important factors. Phonon energy, as a basic property of matrix, greatly affects the temperature-dependent luminous intensity. Herein, Yb3+/Er3+ co-doped NaYF4 (NY), Y2O3 (YO), KLa(MoO4)2 (KLM), LaNbO4 (LN) and LaPO4 (LP) phosphors were used to be experimental objects because the phonon energy of them has distinct gradient. By comparing the sensitivities of Yb3+-Er3+ co-doped different matrices, it is found that the sensitivity is positively correlated with the matching degree (MD) between phonon energy and energy gap (ΔE) of thermal coupled levels (TCLs). This is because of the stronger mismatch between the energy gap and the effective phonon energy makes the non-radiative thermalization rates slower, thus affecting the rate of LIR change. The above conclusion gives a guidance method for selecting suitable matrix of high-sensitivity fluorescent thermometers.