Preparation and characterization of Yb2O3–Al2O3 glasses by the Pechini sol–gel method combined with flame synthesis

Ytterbium–aluminate glass microspheres with the compositions identical to those of the binary Yb3Al5O12–Al2O3 eutectic (79.4 mol% Al2O3 and 20.6 mol% Yb2O3) and of the ytterbium aluminium garnet (62.5 mol% Al2O3 and 37.5 mol% Yb2O3) were studied. The glasses were prepared in the form of microspheres by flame synthesis from a precursor powders synthesised by Pechini sol–gel method. The microspheres consisted of amorphous ytterbium aluminate matrix containing low amount of crystalline phases, namely ytterbium aluminum garnet (YbAG) and α-Al2O3. The influence of glass structure on optical properties was studied. Absorption peaks characteristic for Yb3+ doped glasses centered at 927, 931 and 975 nm were observed for both studied compositions. In polycrystalline samples prepared by controlled crystallisation of the glasses (6 h at 1200 °C in ambient atmosphere) a shift of absorption peaks was observed, with maxima at 934, 969 and 1029 nm.