Properties and Structure of Lanthanum Borate Glasses

Glass formation limits were determined for the lanthanum borate glasses. Stable immiscibility prevents the formation of clear glasses over the range 0 to 20 mol% La₂O₃, but excellent quality glasses could be formed between 20 and 28 mol% La₂O₃. Data are reported for the density, refractive index, thermal expansion coefficient, glass transformation and dilatometric softening temperatures, transformation range viscosity, helium permeability, and chemical durability of these glasses. A limited Raman and infrared spectroscopy study suggests that lanthanum plays a similar structural role in these glasses and in the related crystals.