High sensitive ratiometric optical thermometer based on different multi-photon processes of upconversion luminescence in scheelite Ca1-xMgxWO4:Er3+/Yb3+ phosphors. - Liu, Xinyue; Sun, Chengmei; Xu, Chengcheng; Wang, Qingru; Wang, Kai; Zhang, Dong (Ceramics International, 2024)