Synthesis and Luminescence Characteristics of LaF3:Yb:Er Powders Produced by Coprecipitation from Aqueous Solutions

Hydrated lanthanum fluoride powders, both undoped, and doped with erbium and ytterbium fluorides (to a total content of 6–28 mol %), of the general formula RF 3 · n H 2 O ( n = 0.30 ± 0.01), crystallizing in the hexagonal system, were obtained by coprecipitation from aqueous solutions of the corresponding nitrates by the interaction with hydrofluoric acid. The dehydration is completed at 380°C. At 600°C, the concentrated solid solution decomposes to precipitate a phase with the structure of orthorhombic YF 3 . The efficiency of the upconversion luminescence of the powders, excited at a wavelength of 974 nm, is low.