Controllable synthesis and crystal structure determined upconversion luminescence properties of Tm3+ (Er3+) ions doped YbF3 and NaYbF4 crystals

Highlights
- The synthesis of YbF3 and NaYbF4 crystals was successfully fulfilled by hydrothermal method.
- The phase and morphology of products were adjusted by changing the hydrothermal conditions.
- Relatively enhanced ultraviolet upconversion emissions were observed in YbF3 nanocrystals.
- The crystalline phase impact on the upconversion luminescence was systematically studied.