Thermal image furnace melting and twin-roller quenching were used to prepare glasses containing large amounts of rare earth oxides in Ln₂O₃-M_XO_Y systems (Ln₂O₃=La₂O₃, Nd₂O₃, Y₂O₃; M_XO_Y=SiO₂, Al₂O₃, TiO₂, Nb₂O₅).
The glass-forming regions were found at the following compositions close to the eutectic points of the phase diagrams: (20-30)Ln₂O₃-(70-80)SiO₂, 60Ln₂O₃-40SiO₂, 20Ln₂O₃-80Al₂O₃, 20Ln₂O₃-80 TiO₂, (20-30)Ln₂O₃-(70-80)Nb₂O₅ and 60Ln₂O₃-40Nb₂O₅. The glass transition temperature T_g was determined by DTA. All the glasses showed high glass transition temperatures over 700°C. Although T_g increased or decreased with Ln₂O₃ content depending upon the system, the change was linear with Ln₂O₃ content around the eutectic compositions. This seems to indicate that there is no peculiar behavior of viscosity itself at the eutectic compositions. The liquidus viscosity becomes the maximum at the eutectic compositions due to low liquidus temperatures, which makes glass-formation easier at the eutectic compositions.
A glass model consisting of four-coordinated aluminum units was proposed for Ln₂O₃-Al₂O₃ glasses based on the results of IR spectra and observed AlKα chemical shifts. On the other hand IR spectra of Ln₂O₃-TiO₂ glasses showed a mixture of six- and four-coordinated titanium units.
Visible and ultraviolet absoption spectra of Nd³⁺ were studied on Nd₂O₃-M_XO_Y glasses. The peak positions of these absorption bands moved towards lower wave numbers linearly with increasing compositional basicity of the glasses. Their color changed from purple-like blue to green-like blue, as the absorption bands shifted towards lower wave numbers.