Properties of Yttria‐Aluminoborate Glasses

In the Y 2 O 3 –Al 2 O 3 –B 2 O 3 system, homogeneous glasses were obtained from compositions containing from 50 to 65 mol% B 2 O 3 . The density, refractive index, and thermal expansion increase as Y 2 O 3 replaces either B 2 O 3 or Al 2 O 3 . These glasses have a dilatometric softening temperature above 665°, and below 300°C their dc electrical resistivity exceeds that of fused silica. The infrared absorption spectra indicate that BO 3 , BO 4 , and AlO 4 , groups are present in these glasses.