Microstructure, mechanical and thermal properties of boron oxide added steatite ceramics

Steatite ceramics have been fabricated using coarse starting materials such as talc, clay and barium carbonate with addition of boron oxide (B2O3). Microstructure, mechanical and thermal properties of the steatite ceramics as a function of B2O3 addition have been investigated. B2O3 has been found to be a useful flux to densify MgO–Al2O3–SiO2–BaO (MASB) steatite powders. Highly dense and crystalline ceramics, predominantly composed of protoenstatite and clioenstatite together with small amounts of residual glassy phase, were obtained after sintering at a low temperature such as 1200°C. Scanning electron microscopy (SEM) analysis indicated that large pores were seen in B2O3 free samples, while pore elimination and enhancement of densification for B2O3 added compacts were promoted by the viscous flow of B2O3. Bending strength of the steatite ceramics increased with B2O3 content. The thermal expansion and average linear thermal expansion coefficient of B2O3 free samples were higher than those of B2O3 added compositions.