molecules Article Controlled Synthesis of Tb3+/Eu3+ Co-Doped Gd2O3 Phosphors with Enhanced Red Emission Dong Zhu 1,†, Jinkai Li 1,*,† , Xiangyang Guo 2, Qinggang Li 1, Hao Wu 1,* , Lei Meng 3,* and Zongming Liu 1,* 1 School of Materials Science and Engineering, University...