Structure-Sensitive Properties of Melts and Thermal Properties of Glasses in the B 2 O 3 –CaO–Al 2 O 3 –PbO System

— The devitrification, “cold” crystallization, and glass transition temperatures and melting point of samples in the B 2 O 3 –CaO–Al 2 O 3 –PbO system have been determined by differential thermal analysis. The viscosity of aluminum calcium borate melts containing up to 6.9% PbO has been measured in the temperature range 1153–1573 K. The results demonstrate that lead oxide additions reduce melt viscosity and that the density and surface tension of the melts increase with increasing lead oxide content and decrease with increasing temperature. High- and low-temperature regions have been identified where the melts have properties of Newtonian fluids. Cooling leads to polymerization and vitrification of the melts.