NIR-to-NIR lifetime based thermometry with the thermally elongated luminescence kinetics driven by structural phase transition in LiYO2:Yb3+

TL;DR

This paper introduces a novel NIR-to-NIR luminescence lifetime thermometry method using LiYO2:Yb3+ that exploits a structural phase transition to achieve thermally elongated luminescence kinetics, enhancing temperature sensitivity.

Contribution

It demonstrates a new approach where a structural phase transition in LiYO2:Yb3+ prolongs luminescence lifetime with temperature, improving thermometry sensitivity and enabling ratiometric temperature readout.

Findings

Achieved a relative sensitivity of 0.5%/K using lifetime changes.

Controlled phase transition temperature via dopant concentration.

Enabled ratiometric thermometry with 5.3%/K sensitivity at 280K.

Abstract

Among the various techniques used in luminescence thermometry, luminescence kinetics is considered the least sensitive to perturbations related to the optical properties of the medium containing the phosphor. For this reason, temperature sensing and imaging using lifetime-based luminescence thermometers is of high interest for wide range of specific applications. However, for most such thermometers, an increase in temperature leads to a shortening in lifetime, which can hinder the specificity and accuracy of the readout. In this work, we present an approach that utilizes a thermally induced increase in the symmetry of the host material associated with a structural phase transition in LiYO2:Yb3+. Consequently, the lifetime of the excited level 2F5/2 of the Yb3+ ion is thermally prolonged, achieving a relative sensitivity of 0.5%/K. The phase transition temperature can be controlled by adjusting the dopant concentration. Additionally, thermal changes in the emission spectrum enable the use of LiYO2:Yb3+ for ratiometric temperature readout with a relative sensitivity of 5.3%/K at 280K for LiYO2:5%Yb3+.