Novel Li2Ga0.5Sb0.5O3(Li4GaSbO6):Mn4+ phosphors with multisite occupancy for efficient FIR and luminescence lifetime dual-mode thermometers

Abstract

Growing demand in temperature detection applied to describe physico-chemical state drives the swift development of non-contact luminescent thermometers with outstanding properties containing quick temperature response, high accuracy, high temperature sensitivity and wide temperature detection range. In this work, a series of novel red-emitting Li₄GaSbO₆:Mn⁴⁺ phosphors were synthesized using a high-temperature solid-state reaction method and further devised to applied in the FIR and luminescence lifetime dual-mode thermometers due to their luxuriant luminescence properties. Upon 469 nm excitation, the Li₄GaSbO₆:Mn⁴⁺ presented three apparent emission peaks at 658, 674 and 689 nm, which was demonstrated to be originated from Mn⁴⁺ occupying three kinds of Ga³⁺ and Sb³⁺ sites in the lattice by diverse excitation, emission and decay curves. Based on this, the temperature-dependent emission spectra showed that the emission intensity and decay lifetime of these three peaks presented different decreasing trend with increasing temperature, which can be served as potential application for the FIR technology and fluorescent lifetime thermometers. Simultaneously, the double modes for temperature detection will enhance the accuracy of temperature detection. Results show that the maximal relative temperature sensitivity S_r is 0.64 % K⁻¹ and 2.82 % K⁻¹ for FIR and lifetime-based modes thermometry, respectively, which illustrate that as-prepared phosphors could be potentially sensing materials applied in fluorescence thermometer.