Impact of Negative Thermal Expansion on Thermal Quenching of Luminescence of Sc2Mo3O12:Eu3+

Thermal quenching (TQ) is a major challenge facing many phosphors, especially those used in the high-temperature range. To overcome this obstacle, here we present a new phenomenon of excitation-wavelength-dependent antithermal quenching (anti-TQ) luminescence over a broad temperature range. We have observed that the luminescence intensity of Eu 3+ -doped Sc 2 Mo 3 O 12 almost triples at elevated temperatures along with intensified energy transfer from the host to the dopant upon excitation at the charge-transfer band of 277 nm. Specifically, the absolute emission intensity of Sc 2 Mo 3 O 12:20%Eu 3+ measured at 398 and 798 K reaches 292% and 97% of its initial intensity taken at 298 K, respectively. Similar to the photoluminescence emission intensity, the lifetime also elongates upon heating with a maximum value at 623 K. We have unveiled the mechanism of the excitation-wavelength-dependent anti-TQ luminescence, which is attributed to the promoted energy transfer induced by the negative thermal expansion (NTE) property of the Sc 2 Mo 3 O 12 host. Moreover, we have demonstrated the efficient high-temperature luminescence thermometric performance of this anti-TQ luminescence phosphor using its temperature-dependent lifetime. The new phenomenon and experimental findings presented in this study provide inspiration for the future exploration of NTE-based phosphors with thermally enhanced luminescence performance via their intensified energy transfer for broad potential applications.