Phase transformation and enhancement of luminescence in the Tb3+-Yb3+ co-doped oxyfluoride glass ceramics containing NaYF4 nanocrystals

Cubic-to-hexagonal phase transformation and enhancement of upconversion emission are simultaneously achieved by modifying the ratio of ZnO/Na2O content in the Tb3+-Yb3+ co-doped oxyflouride Zincatesilion glass ceramics containing NaYF4 nanocrystals. XRD and TEM data have revealed that the crystallization of NaYF4 from α phase to β phase. Additionally, upconversion emissions were obtained from these Tb3+-Yb3+ glass ceramics under 980 nm excitation. Compared with the cubic α-NaYF4 nanocrystals of glass ceramics, the upconversion intensity augmented drastically owing to the phase transformation that the NaYF4 has changed from α into β. Therefore, the PL results showed that the cubic-to-hexagonal the NaYF4:Eu3+ lattice could induce a remarkable change of the PL intensity in red region (R = IED/IMD) with 393 nm excitation wavelength. It was indicated that it changed the phase transformation in Tb-Yb on symmetry of the lattice.