Giant thermal enhancement of upconversion photoluminescence in Y2W3O12:Nd phosphor under 808 nm excitation

Luminescent materials usually suffer from thermal quenching at high temperature due to the aggravation of nonradiation relaxations. Herein, a giant enhancement of up conversion (UC) luminescence is observed in negative thermal expansion (NTE) Y2W3O12:Nd phosphor upon increasing the temperature from 310 to 790 K. In addition, the temperature-dependent UC emission is reversible. To penetrate into the mechanisms, the temperature-dependent luminescence intensity and lifetime are investigated for Nd doped negative and positive thermal expansion (PTE) phosphors. Based these investigation, we infer that the underlying mechanism of the giant enhancement for Y2W3O12:Nd phosphor are due to combined effects of phonon assisted absorptions and contraction of NTE crystals. Moreover, the observation of temperature-dependent near-infrared spectra (NIR) can support the mechanism from the other side. The present findings pave the way to overcome thermal quenching of Nd3+ ions and explore new thermal enhancement materials sensitized by Nd3+ ions.