Phase transition control, melt growth of (Gd,RE)F₃ single crystal and their luminescent properties

Rare-earth sesquifluorides with no absorption in visible spectral region, such as LaF₃, GdF₃, LuF₃, YF₃, ScF₃, are the topic of intense study as a host for luminescence materials. However, except Nd:LaF₃, they are not studied as a host for laser materials. The main obstacle troubling further study of GdF₃, LuF₃, YF₃, ScF₃ single crystal is the fact that there is first-order phase transition (LaF₃ type↔beta-YF₃ type for GdF₃, alpha-YF₃ type↔beta-YF₃ type for the rest) between the room and melting temperature.To prevent the phase transition, first of all, we have tried to make solid solution between GdF₃ and YF₃ in such a way that the average cation radii can be shifted to the size that does not have phase transition. Ce³⁺ perturbed luminescence was observed in the Ce- and Sr-codoped GdF₃-YF₃ system. Similar solid solution concept was applied to the combination between GdF₃ and YbF₃. The emission spectrum of Yb³⁺ that exhibits broad bands around 1 μm was observed. Room temperature up-conversion luminescence spectra of Pr³⁺-doped Gd_1-xYb_xF₃ were studied and visible emission from Pr³⁺ was obtained under infrared laser pumping in the Yb³⁺ broad absorption band at 935.5 nm.