Role of the Nephelauxetic Effect in Engineering Mn4+ Luminescence Kinetics for Lifetime-Based Thermometry

TL;DR

This work develops a theoretical model linking the nephelauxetic effect to Mn4+ luminescence kinetics, enabling better design of lifetime-based thermometers in double perovskites.

Contribution

It introduces a predictive model based on the nephelauxetic beta1 parameter for designing Mn4+ luminescent thermometers, challenging previous assumptions about the Dq/B ratio.

Findings

The nephelauxetic beta1 parameter dominates thermometric performance.

The Dq/B ratio is not the primary factor influencing Mn4+ luminescence.

A new predictive model estimates thermometric sensitivities from beta1.

Abstract

Although the considerable potential of luminescence thermometry based on emission kinetics has been widely demonstrated, reliable tools for the intentional prediction of thermometric performance remain limited. To address this challenge, the present work introduces an approach that enables a theoretical description of the 2E state lifetime of Mn4+ ions, as well as the absolute and relative sensitivities, in terms of the nephelauxetic effect within the group of double perovskites: Sr2InNbO6, Sr2InTaO6, Ba2InTaO6, and Ba2InNbO6. Our results clearly show that, contrary to common assumptions, the Dq/B ratio is not the primary factor governing either the spectroscopic behavior of Mn4+ ions or the thermometric performance of Mn4+-doped phosphors. Instead, the nephelauxetic beta1 parameter plays the dominant role. The empirical analysis carried out in this study led to the development of a predictive model that enables estimation of SAMAX and SRMAX values based exclusively on beta1. This methodology represents a significant step toward the rational design of lifetime-based luminescence thermometers with predefined thermometric characteristics tailored to the requirements of specific applications.