Anti-thermal quenching of luminescence in YWO:Yb/RE (RE = Er/Ho/Tm) and its temperature sensing application.

Herein, a series of YWO:10%Yb/%RE (RE = Er/Ho/Tm) phosphors is prepared a solid-state reaction. The upconversion and downshift luminescence properties of the phosphors were investigated under an excitation of 980 nm. The bright blue light emission from Tm ion and the green and red light emissions from Ho(Er) ions were observed. The near-infrared light intensity of NIR-I (Tm, ∼850 nm), NIR-II (Er: ∼1550 nm; Tm: ∼1783 nm) and NIR-III (Ho: ∼2050 nm) were analyzed. In particular, the dramatic thermal enhancement phenomenon in visible and NIR regions was exhibited by the YWO:10%Yb/%RE (RE = Er/Ho/Tm) phosphors. Among them, the green light intensity of Er ions increased 26.77 times, from 303 to 573 K. The NIR-II emission band (∼1783 nm) intensity of Tm ions at 533 K increased 168.7 times compared to that at 313 K. The possible thermal enhancement mechanism is illustrated by the negative thermal expansion (NTE) and Frenkel defect of the YWO host. Finally, the optical temperature sensing performances of YWO:10%Yb/%RE (RE = Er/Ho/Tm) samples are investigated according to the luminescence intensity dependence relationship on temperature. The maximum value of reached 4.24% K at 353 K for YWO:10%Yb/0.6%Ho phosphor. The results indicate that the YWO:10%Yb/%RE (RE = Er/Ho/Tm) phosphors possess anti-thermal quenching properties and are suitable for developing optical temperature sensors.