Investigation on the determinant of upconversion luminescence efficiency and temperature measurement sensitivity based on AWO4 (Ba, Sr, Ca, and Mg): Er3+/Yb3+ microcrystals

In this work, a comparative study of the upconversion (UC) luminescence properties of E r 3 + − Y b 3 + -co-doped A W O 4 ( A = B a , Sr, and Ca) scheelite phosphors and E r 3 + − Y b 3 + -co-doped M g W O 4 wolframite phosphors is reported. Under 980 nm excitation, all the samples emit green and red emissions. The E r 3 + − Y b 3 + -doped M g W O 4 phosphor has a higher UC emission intensity. Furthermore, the optical temperature sensing properties in E r 3 + − Y b 3 + -co-doped A W O 4 ( A = B a , Sr, Ca, and Mg) phosphor samples are investigated. The relative sensitivity ( S r ) based on thermally coupled levels (TCLs) increases gradually with an increase in matrix phonon energy. The absolute sensitivity ( S a ) values of the samples are accurately predicted by the chemical bonding parameter ( f c ). The results of the correlation between the UC luminescence properties and the microscopic crystal structure, and the relationship of the temperature sensitivity and the host parameters, provide us with a guiding insight for the selection of a host material with ideal temperature measurement capability.