Low-temperature densification sintering and properties of CaAl₂Si₂O₈ ceramics with MeO·2B₂O₃ (Me = Ca, Sr, Ba)

Dense CaAl₂Si₂O₈ ceramics were prepared via a two-step sintering process at temperatures below 1000℃. First, pre-sintered CaAl₂Si₂O₈ powders containing small amounts of other crystal phases were obtained by sintering a mixture of calcium hydroxide and kaolin powders at 950℃ for 6 h. Subsequently, the combination of the pre-sintered ceramic powders with MeO·2B₂O₃ (Me = Ca, Sr, Ba) flux agents enabled the low-temperature densification sintering of the CaAl₂Si₂O₈ ceramics at 950℃. The sintering behavior and phase formation of the CaAl₂Si₂O₈ ceramics were investigated in terms of the addition of the three MeO·2B₂O₃ flux agents. Furthermore, alumina and quartz were introduced into the three flux agents to investigate the sintering behaviors, phase evolvements, microstructures, and physical properties of the resulting CaAl₂Si₂O₈ ceramics. The results showed that, because of their low-melting characteristics, the MeO·2B₂O₃ (Me = Ca, Sr, Ba) flux agents facilitated the formation of the CaAl₂Si₂O₈ ceramics with a dense microstructure via liquid-phase sintering. The addition of alumina and quartz to the flux agents also strongly affected the microstructures, phase formation, and physical properties of the CaAl₂Si₂O₈ ceramics.