A strategy for enhancing luminescence thermometry via Ta5+-triggered K0.5Na0.5NbO3: Er3+ transparent ceramics

Abstract

Luminescence thermometry is a reliable approach for remote thermal sensing, and extensive studies have been devoted to designing a luminescence thermometer with heightened thermal sensitivity. Herein, we report a promising luminescence thermometric material, Ta5+-substituted K0.5Na0.5NbO3:0.003Er3+ transparent ferroelectric ceramics. The temperature sensing sensitivity is significantly improved by adjusting the concentration of Ta5+ in the material. Specifically, utilizing the fluorescence intensity ratio from the 2H11/2 and 4S3/2 thermally coupled states of Er3+ as a detecting signal within the temperature range of 273–543 K, an optimal maximum absolute sensitivity of 0.0058 K–1 and relative sensitivity of 0.0158 K–1 are achieved for K0.5Na0.5NbO3: 0.65Ta5+/0.003Er3+. Simultaneously, as the concentration of Ta5+ increase, a unique evolution of structural phase transitions is observed from orthorhombic to tetragonal and then to cubic. This is accompanied by an improvement in luminescence temperature sensing properties, and the best sensitivity is demonstrated in the cubic-phase region. Intriguingly, a huge change in infrared luminescence properties as a function of temperature is found around the structure transition temperature of the samples. These results indicate a promising potential for achieving highly sensitive thermometry or monitoring phase structure transitions through luminescence thermometry behavior in the K0.5Na0.5NbO3 host.