Effect of ligand environment of rare-earth ions on temperature measurement performance of SrAO4:xEu3+ (A = Mo and W) phosphors

Molybdate and tungstate with scheelite-type structure are excellent self-luminescent materials, which can be used as ideal hosts for the doping of rare-earth ions. In this study, a series of Eu 3+ -activated SrAO 4 (A = Mo and W) phosphors were successfully synthesized, and their crystal structures, photoluminescence properties, and temperature measurement performance were analyzed in detail. These phosphors were excited by UV light (291 nm and 247 nm, respectively), with clear energy transfer (ET) (MoO 4 2− →Eu 3+ or WO 4 2− →Eu 3+ ). According to fluorescence intensity ratio (FIR) and Judd–Ofelt (J–O) theory, compared to SrWO 4 :0.01Eu 3+ phosphor, SrMoO 4 :0.01Eu 3+ phosphor exhibited better thermal stability, with relatively low Sa value (maximum values were 5.082 %K −1 and 20.74 %K −1 , respectively), and their Sr values were not significantly different (maximum values were 0.864 %K −1 and 0.83 %K −1 , respectively). Sa value was negatively correlated to central asymmetry of Eu 3+ , but the optimal Sr value tended to be more suitable for central asymmetry of Eu 3+ . In addition, Eu 3+ exhibited stronger central asymmetry as well as covalency of Eu–O bond in SrMoO 4 . Results reveal that SrMoO 4 :xEu 3+ and SrWO 4 :xEu 3+ can be used for luminescent thermometers.