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arXiv · 2512.09581

Structural Phase Transition and Cooperative Luminescence in K3Yb(PO4)2:Eu3+ for Multimodal Down-shifting and Up-converting Luminescence Thermometry

Anam Javaid·Maja Szymczak·Damian Szymanski·Lukasz Marciniak
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Abstract

To develop a more universal luminescent thermometer that provides both high relative sensitivity and the ability to measure temperature across different spectral ranges and excitation wavelengths, the K3Yb(PO4)2:Eu3+ system was proposed in this work. It was demonstrated that this material undergoes a structural phase transition from the monoclinic to the hexagonal phase above 450 K. This transition enabled the construction of a ratiometric, phase-transition-based thermometer utilizing the luminescence intensity ratio of Stark lines of Eu3+ and Yb3+ ions, which exhibit SRmax values of 4.2% K^-1 and 1.15% K^-1, respectively. Moreover, increasing the Eu3+ ion concentration was shown to raise the phase transition temperature, thereby shifting the thermal operating range of both luminescent thermometers. Under 980 nm excitation, K3Yb(PO4)2:Eu3+ exhibits both cooperative luminescence from Yb3+ pairs and up-conversion emission from Eu3+ ions. Increasing the Eu3+ concentration enhances the Eu3+ luminescence intensity relative to the cooperative luminescence of Yb3+ pairs, resulting in a change in the emitted light color. The difference in the thermal quenching behavior of these two signals further enabled the development of a ratiometric thermometer with SRmax = 0.58% K^-1. These findings identify K3Yb(PO4)3:Eu3+ as a promising candidate for multimodal temperature sensing.

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Anam Javaid, Maja Szymczak, Damian Szymanski, Lukasz Marciniak. 2025-12-10. Structural Phase Transition and Cooperative Luminescence in K3Yb(PO4)2:Eu3+ for Multimodal Down-shifting and Up-converting Luminescence Thermometry. https://arxiv.org/abs/2512.09581

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