Exploration of High-Hardness/Low-Melting Borate Glasses

Numerous types of borate glass-AEO-ZnO-B2O3 (AEO = CaO, SrO, BaO), TMO-ZnO-B2O3 (TMO = MnO, Fe2O3, Co3O4, NiO, CuO), and REO-TMO-B2O3 (REO = Nd2O3 and La2O3)-were investigated to discover a glass with high hardness and low melting temperature. They were prepared using a combinatorial glass melting system, and their hardness and glass transition temperature, T-g, were measured. The REO-TMO-B2O3 glass systems had higher hardness than the other glass systems due to the large packing density of the glasses. In particular, the hardness values of the REO-NiO-B2O3 glasses were >8 GPa, with T-g values of about 650 degrees C. The REO-NiO-B2O3 glasses are good candidates for high-hardness and low-melting-temperature glasses. Among glasses having a T-g <550 degrees C, Fe2O3-ZnO-B2O3, Co3O4-ZnO-B2O3, and REO-MnO-B2O3 glasses had hardnesses >6 GPa.