# Comment on a zero-thermal-quenching phosphor

## TL;DR

This paper critically examines a claimed zero-thermal-quenching phosphor, revealing that its supposed non-quenching behavior is likely due to experimental artifacts rather than intrinsic material properties.

## Contribution

The study challenges previous claims of zero thermal quenching in a specific phosphor by providing a detailed optical analysis and identifying potential measurement pitfalls.

## Key findings

- Observed increase in emission intensity with temperature is likely an experimental artifact.
- Optical characterization points to thermal expansion and phase transitions affecting measurements.
- Claims of zero thermal quenching are not supported by comprehensive optical data.

## Abstract

Kim and co-authors in a recent article reported a phosphor Na3-2xSc2(PO4)3:xEu2+ (NSPO:xEu2+) that did not exhibit thermal quenching (TQ) even up to 200 degree Celsius. The authors suggested that zero-TQ originates from the compensation of emission losses due to the polymorphic nature of the host and the energy transfer from traps consisting of electron-hole pairs to the 5d-band of Eu2+, leading to radiative recombination. The temperature-dependent excitation and emission spectra seemingly supported the authors' assertion. However, a close inspection of the CIE chromaticity coordinates and correlated color temperature (CCT) the WLED prototype fabricated using NSPO:0.03Eu2+ , La3Si6N11:Ce3+ and (SrCa)AlSiN3:Eu2+ as a blue, yellow and red-emitting component respectively (abbreviated as WLED device hereafter) under operating currents of 100-1000 mA alongside a series of optical characterization results of NSPO:xEu2+ indicates that the so-called zero-TQ should not be the case. There were some questionable points in optical characterization of the phosphors. The observed increase in intensity upon elevating temperature in the temperature-dependent excitation and emission spectra was likely a pitfall caused by optical path length variation of the spectrofluorimeter induced by lattice thermal expansion and phase transitions.

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Source: https://tomesphere.com/paper/1904.08769