Synthesis and optical characterizations of Yb-doped CaF2 ceramics

Nanopowders of Yb-doped calcium fluoride were obtained by three different ways: mechanical alloying, reverse micelle method and co-precipitation. Transmission electron microscopy showed that the particle sizes were monodispersed for the powders obtained from soft chemistry with an average size around 20 nm and polydispersed for the powder from the chemical alloying. An annealing step at 400 °C is needed to remove impurities adsorbed at the particles surface for powders obtained from the reverse micellar and the co-precipitation methods. Transparent ceramic with a grain mean size of 24 μm was obtained from the co-precipitation synthesized powder after a vacuum sintering followed by a HIP post-treatment. Loss of transmission can be attributed mainly to the presence of a residual closed porosity. The best transmission value is 55% reached in the infrared range at 1.2 μm.