Compositional Effects on the Properties of Si‐Al‐RE‐Based Oxynitride Glasses (RE = La, Nd, Gd, Y, or Lu)

A series of silicon‐aluminum oxynitride‐glass compositions containing selected rare‐earth (RE) additions were prepared to examine the effects of specific RE, as well as Si:Al:RE and N:O ratio, on properties. The properties that were characterized included density, thermal expansion coefficient (α), glass‐transition temperature ( T g ), hardness ( H ), and Young's modulus ( E ). The compositions (in equivalent percent) selected included: 55 Si‐20 RE‐25 Al oxide and 80 O‐20 N oxynitride, and 45 Si‐30 RE‐25 Al oxide and 70 O‐30 N glasses. The results show that the density increased significantly with an increase in the RE atomic mass and slightly with an increase in N:O ratio. For each of the fixed Si‐Al‐RE‐O‐N compositions, the E , H , and T g values were each increased by substituting smaller RE ions, whereas the α value was decreased. For each specific cation composition and RE, increasing the N:O ratio systematically led to a decrease in the α values but an increase in the E , H , and T g values. The observed response in the glass properties to changes in composition appears to reflect modifications in the bonding within the glass network.