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 Gd1−xYbxF3 were studied and visible emission from Pr3+ was obtained under infrared laser pumping in the Yb3+ broad absorption band at 935.5 nm.