Effect of molybdenum and titanium oxides on mechanical and thermal properties of cordierite–enstatite glass-ceramics

By adding either MoO3 or TiO2 as nucleating agents, glass at the eutectic point of cordierite (2MgO·2Al2O3·5SiO2) and enstatite (MgSiO3) in the MgO–Al2O3–SiO2 ternary system was crystallized. Although bulk crystallization required adding 10wt% TiO2, approximately 0.1–0.5wt% of MoO3 induced bulk nucleation when the parent glass was melted under reducing conditions. For both TiO2- and MoO3-nucleated glasses, the glass-ceramics containing both cordierite–enstatite as main crystalline phases were obtained by heat-treatment at 1200°C. The fracture toughness of the glass-ceramics nucleated by TiO2 was 1.5 times higher than that of sintered cordierite ceramics. In addition to two main crystalline phases, magnesium titanium oxide and rutile also precipitated in TiO2-nucleated glass. The additional effects of TiO2 on the properties of the glass-ceramics were identified by comparing the TiO2- nucleated glass-ceramics and MoO3- nucleated one. The addition of TiO2 slightly increased the Young's modulus of the glass-ceramics. On the other hand, since TiO2 suppressed the precipitation of enstatite, the thermal deformation of TiO2-nucleated glass-ceramic at 1100°C was larger than that of MoO3- nucleated one. Therefore, MoO3 is the preferable nucleating agent of the glass-ceramics for application which requires high thermal endurance. •Bulk crystallized coedierite–enstatite glass-ceramics were prepared.•Bulk crystallization occurred by addition of 0.5wt% of MoO3 as a nucleating agent.•The glass-ceramics prepared by addition of MoO3 showed less thermal deformation.•TiO2 slightly increased Young's modulus of the glass-ceramics.