Second-Coordination-Sphere Cation Substitution as a Tool for Controlling Phase Transitions and Performance of the Luminescence Thermometry
Title: Second-Coordination-Sphere Cation Substitution as a Tool for Controlling Phase Transitions and Performance of the Luminescence Thermometry
Authors: M. T. Abbas, M. Szymczak, M. Fandzloch, D. Szymanski, A. Sieradzki, L. Marciniak*
Journal: Chemistry of Materials
DOI: 10.1021/acs.chemmater.6c00512
One of the main limitations of luminescent thermometers based on structural phase transitions is their inherently narrow thermal operating range. Our previous studies demonstrated that doping with lanthanide ions enables tuning of the phase transition temperature and, consequently, adjustment of the thermal operating range. However, due to the relatively small difference in ionic radii between the host cation (in this case Y3+ ions in LiYO2) and lanthanide ions, relatively high dopant concentrations are required to achieve a significant shift of the phase transition temperature.
In the present work, we demonstrate that substituting Li+ ions with Na+ ions provides not only a more cost-effective solution, but, more importantly, a more efficient one. Owing to the substantial difference in ionic radii between Li+ and Na+, significantly lower dopant concentrations are sufficient to induce pronounced changes in the thermal operating range of the thermometer.
At the same time, the study provides important insight into the structural consequences of such modifications. The incorporation of Na+ ions introduces increased compositional disorder and local lattice strain, which reduce the enthalpy difference between competing phases and weaken the cooperativity of the structural transformation. As a result, the first-order character of the phase transition becomes less pronounced.
These findings highlight a fundamental trade-off: while compositional engineering enables effective tuning of the operating temperature range, it also leads to a reduction in relative sensitivity. The present work therefore offers both a practical strategy for material design and a deeper understanding of the relationship between structural disorder and thermometric performance in phase-transition-based luminescent systems.
This work was supported by the National Science Center (NCN) Poland under project no. DEC-UMO-2022/45/B/ST5/01629
