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For the meting process of glass-ceramics, the melts are simulated by using analytically pure materials high temperature. The effects of La2O3 on the viscosity and structure for the CaO-SiO2-MgO-Al2O3 melt are studied via both rotating-cylinder method and Raman spectroscopy. The results show that the viscosity and viscous flow activation energy decreases as the La2O3 content increases. The addition of La2O3 destroyed the silicate structural units(Qn)m the met. The percent of Q¹,Q² units increases with increasing amount of La2O3. However, the percent of Q³ units decreases with increasing amount of La2O3. In addition, the percent of Q0 units are slightly dependent on the La2O3 content. It indicates that the addition of La2O3 increase the number of non-bridging oxygen in the state structural units and reduce the degree of polymerization. La2O3 pay a role as network modifier in the melt. [ABSTRACT FROM AUTHOR]

• Nb is mainly in the +5 valence state and exists in the form of [NbO 6 ]7− octahedron. • The melt conductivity increases with the increase of Nb 2 O 5 content. • Ti in the melt is dominated by Ti4+ and exists in the [TiO 6 ]8− octahedron structure. Electrical conductivity is a very important physical parameter in the process of electrolytic extraction of niobium from molten niobium-enriched slag or preparation of ferroniobium alloy by reduction melting separation in electric arc furnace. The effects of Nb 2 O 5 , CaO/SiO 2 ratio and TiO 2 on the electrical conductivity of CaO-SiO 2 -Nb 2 O 5 -TiO 2 -CeO 2 -CaF 2 melt were studied by AC four-electrode method. The melt structure was studied by XPS to reveal the change rules of melt conductivity. The results show that the addition of Nb 2 O 5 or increasing the CaO/SiO 2 ratio in the melt can depolymerize the melt network structure and effectively improve the melt conductivity, and the activation energy of the conductivity is negatively correlated with the Nb 2 O 5 content and the CaO/SiO 2 ratio. With the increase of TiO 2 content in the melt, the melt network structure polymerizes, the melt conductivity decreases, and the activation energy of conductivity also showed a decreasing trend. [ABSTRACT FROM AUTHOR]

• The viscosity was proportional to the CeO 2 content and the CeO 2 /Al 2 O 3 ratio. • CeO 2 made the structure of the silicon oxide ionic group to be simple. • The viscosity of the melt was influenced by the combination of Ce4+ and Ce3+. The effect of the CeO 2 content and CeO 2 /Al 2 O 3 ratio on the melt viscosity of CaO-SiO 2 (-Al 2 O 3)-CeO 2 was determined using the rotating cylinder method. The structural characteristics of the quenched vitreous samples were investigated with a Raman spectrometer. The results showed that the melt viscosity of CaO-SiO 2 (-Al 2 O 3)-CeO 2 decreased significantly with increases in the CeO 2 content and the CeO 2 /Al 2 O 3 ratio. Q 3/ Q 2, which represents the degree of polymerization of the melt, decreased with an increase in the CeO 2 content and the CeO 2 /Al 2 O 3 ratio. Ce in the CaO-SiO 2 (-Al 2 O 3)-CeO 2 system was present as a mixture of Ce4+ and Ce3+ in high-purity Ar atmosphere at a temperature of 1540 °C. In the CaO-SiO 2 (-6%Al 2 O 3)-6%CeO 2 system, the melt viscosity was higher in the presence of Ce4+ and Ce3+ than in the presence of Ce3+, indicating that the melt viscosity of CaO-SiO 2 (-Al 2 O 3)-CeO 2 was determined by the combination of Ce4+ and Ce3+. CeO 2 acted as a network modifier in the melt. [ABSTRACT FROM AUTHOR]