Effects of rare earth oxides (La₂O₃, Gd₂O₃) on optical and thermal properties in B₂O₃-La₂O₃ based glasses

摘要

The optical and thermal properties of B₂O₃-La₂O₃ based glasses, designed for digital imaging lenses, were investigated as a function of the Gd/(La+Gd) ratio in the glasses. The refractive index decreased gradually with increasing Gd/(La+Gd) ratio, although the change of refractive index was small. The liquidus temperature (LT) showed a minimum of 970°C for the glass with a Gd/(La+Gd) ratio of 0·5. The viscosity at the LT reached a maximum for the glass with a ratio of 0·5, although the viscosity determined at 1040°C for the glasses was found to increase gradually with increasing Gd/(La+Gd) ratio. X-ray diffraction measurements indicated that the crystalline phase in the glasses below the LT depended strongly on the Gd/(La+Gd) ratio. The effect of the Gd/(La+Gd) ratio on the refractive index, dispersion, density, LT and viscosity is discussed in terms of glass structure.