Simultaneous Thermal Enhancement of Upconversion and Downshifting Luminescence by Negative Thermal Expansion in Nonhygroscopic ZrSc(WO₄)₂PO₄:Yb/Er Phosphors

We report a nonhygroscopic ZrSc(WO4)(2)PO4:Yb3+/Er3+ (ZSWP:Yb/Er) phosphorwith a negative thermal expansion property that exhibits the simultaneousthermal enhancement of upconversion and downshifting luminescenceperformance. On the basis of the fluorescence intensity ratio technique,the high S (a) and S (r) values of ZSWP:Yb/Er are revealed in the application of luminescencethermometry. Thermal quenching (TQ) is still a critical challengefor lanthanide(Ln(3+))-doped luminescent materials. Herein, we report thenovel negative thermal expansion nonhygroscopic phosphor ZrSc(WO4)(2)PO4:Yb3+/Er3+. Upon excitation with a 980 nm laser, a simultaneous thermal enhancementis realized on upconversion (UC) and downshifting (DS) emissions fromroom temperature to 573 K. In situ temperature-dependentX-ray diffraction and photoluminescence dynamics are used to revealthe luminescence mechanism in detail. The coexistence of the highenergy transfer efficiency and the promoted radiative transition probabilitycan be responsible for the thermally enhanced luminescence. On thebasis of the luminescence intensity ratio of thermally coupled energylevels H-2(11/2) and S-4(3/2) at different temperatures, the relative and absolute sensitivitiesof the targeted samples reach 1.10% K-1 and 1.21%K-1, respectively, and the low-temperature uncertaintyis approximately 0.1-0.4 K on the whole temperature with ahigh repeatability (98%). Our findings highlight a general approachfor designing a hygro-stable, thermostable, and highly efficient Ln(3+)-doped phosphor with UC and DS luminescence.