Expanding the horizons of phase transition-based luminescence thermometry

Abstract

The limited operational range of phase transition-based luminescence thermometers necessitates the exploration of new host materials exhibiting first-order structural phase transitions to broaden the applicability of this approach. Addressing this need, the present study investigates the spectroscopic properties of LaGaO₃:Eu³⁺ as a function of temperature. A thermally induced structural transition from the low-temperature orthorhombic phase to the high-temperature trigonal phase, occurring at approximately 430 K, significantly alters the spectroscopic properties of Eu³⁺ ions. Specifically, a reduction in the number of Stark lines due to changes in the point symmetry of Eu³⁺ ions enables the development of a ratiometric luminescence thermometer with sensitivity as high as S_R = 6% K⁻¹ at 480 K. Furthermore, it was demonstrated that increasing the concentration of Eu³⁺ ions shifts the phase transition temperature, allowing for modulation of the thermometric performance of this luminescence thermometer. The findings presented here not only expand the repertoire of phase transition-based luminescence thermometers but also illustrate how the luminescence properties of Eu³⁺ ions can be employed to accurately monitor structural changes in the host material.