Synthesis, electronic polarizability and β-BaB2O4 crystallization in BaO–B2O3–TeO2 glasses

Glasses with the compositions of xBaO–xB2O3–(100-2 ×)TeO2 with x = 15–40 mol% were prepared by using a conventional melt quenching method, and their optical properties, electronic polarizability, and crystallization behavior were examined. The electronic polarizability and optical basicity of the glasses are relatively large (e.g., Λ(no) = 0.856–0.970), indicating that all glasses prepared are regarded as basic (high polarizable) glasses. In the crystallization of 40BaO–40B2O3–20TeO2 glass, both TeO2 and β-BaB2O4 (β-BBO) crystals are formed almost simultaneously. The formation of β-BBO nanocrystals with a diameter of around 5 nm was confirmed from the transmission electron microscope observations, and a hetero-epitaxial crystal growth between TeO2 and β-BBO crystals was suggested. The glass-ceramics with β-BBO crystals exhibited second harmonic generations, although they are not transparent.