A novel Gd-based phosphor NaGdGeO4:Bi3+,Li+ with super-long ultraviolet-A persistent luminescence - Liu, Lin; Yu, Kexin; Ming, Liyan; Sheng, Yangyang; Zheng, Shenghui; Song, Liang; Shi, Junpeng; Zhang, Yun (JOURNAL OF RARE EARTHS, 2022)