Temperature sensitivity of Nd3+, Yb3+:YF3 ratiometric luminescent thermometers at different Yb3+ concentration

Abstract

Nd 3+ (0.5 mol.%), Yb 3+ (1.0, 2.0, 3.0, 4.0, and 8.0 mol.%):YF 3 phosphors were synthesized using a co-precipitation method with subsequent hydrothermal treatment and annealing in vacuum. The Nd 3+ , Yb 3+ :YF 3 phosphors are orthorhombic phase nano-crystals. Luminescence intensity ratio (LIR) of Nd 3+ ( 4 F 3/2 – 4 I 9/2 , ~866 nm) and Yb 3+ ( 2 F 5/2 – 2 F 7/2 , ~980 nm) emissions was chosen as temperature-dependent parameter. The energy exchange between 4 F 3/2 (Nd 3+ ) and 2 F 5/2 (Yb 3+ ) is phonon-assisted which explains the temperature dependence of LIR. There are Nd 3+ to Yb 3+ energy transfer (ET), Yb 3+ to Nd 3+ back energy transfer (BET) and energy diffusion (ED) between Yb 3+ ions. The probability of BET decreases with the increase of Yb 3+ concentration which leads to LIR dependence on Yb 3+ concentration. The maximum absolute temperature sensitivity (S a ) was achieved for Nd 3+ (0.5%), Yb 3+ (1.0%):YF 3 (S a = 0.0018 K −1 at 148 K). The studied samples demonstrate high stability after 8 cooling-heating cycles. The Nd 3+ (0.5%), Yb 3+ (1.0%):YF 3 phosphors are very promising for temperature sensing. • Nd 3+ (0.5 mol.%), Yb 3+ (1.0, 2.0, 3.0, 4.0, and 8.0 mol.%):YF 3 phosphors are orthorhombic phase nano-crystals. • The maximum absolute temperature sensitivity is achieved for Nd 3+ (0.5%), Yb 3+ (1.0%):YF 3 (S a = 0.0018 K −1 at 148 K). • The temperature sensitivity dependence on Yb 3+ concentration is explained by energy exchange between Nd 3+ and Yb 3+ .