The Institute

Title: Phase transition under control: Toward application-oriented luminescence thermometry and thermally activated emission

Authors: M.T. Abbas, M. Szymczak, D. Szymanski, J. Zeler, M. Drozd, L.T.K. Giang, L. Marciniak

Journal: Chemical Engineering Journal

DOI: https://doi.org/10.1016/j.cej.2025.170567

In this work, Prof. Marciniak’s group investigated the influence of phosphor morphology and co-dopant ion concentration on the thermometric properties of LaGaO₃:Eu³⁺, demonstrating its potential for applications in luminescent thermometry and thermally activated luminescence. Specifically, it was shown that a reduction in particle size leads to an increase in relative thermal sensitivity and significantly narrows the hysteresis loop. As a result of this approach, the relative sensitivity was increased to 18.2 % K^-1 for LaGaO₃:Eu³⁺ synthesized via the solid-state method, compared to 3.0 % K^-1 for the counterpart prepared using the Pechini method. Furthermore, we show that the intentional incorporation of Al³⁺ and Sc³⁺ co-dopant ions allows for continuous tuning of the structural phase transition temperature from 165 K for 15 % Al³⁺ to 491 K for 2 % Sc³⁺, without significantly affecting the low-temperature spectroscopic properties of Eu³⁺ ions. This ability to shift the phase transition temperature in LaGaO₃ offers a practical route to modulate the thermal response range of the luminescent thermometer, enabling its adaptation to specific application requirements. The empirical relationship established in this study between the phase transition temperature and the ionic radius mismatch parameter provides a predictive tool for the rational design of phase-transition-based phosphors with tailored thermometric performance. The ability to systematically tune the phase transition temperature via ionic radius mismatch, together with enhanced thermometric performance resulting from reduced grain size dispersion, establishes a coherent strategy for the rational design of high-sensitivity, low-hysteresis thermal sensors. These results lay the groundwork for the development of application-specific luminescent thermometers with tailored operating ranges and improved reliability.

The details of these studies have been published in Chemical Engineering Journal.

This work was funded by the NCN Opus project UMO- 2022/45/B/ST5/01629.