Sintering behavior in zirconium phosphate bonded silicon nitride porous ceramics

A new method for preparing high bending strength porous silicon nitride ceramics with controlled porosity has been developed by using a pressureless sintering technique with zirconium phosphate (ZrP2O7) as a binder phase. The sintering behavior in these porous ceramics is investigated in this study by using XRD, SEM, and HRTEM analysis. The results show that the sintering process can be divided into two stages: one is at temperatures below 250 °C, during which ZrO2 can react completely with H3PO4 to form ZrP2O7, and a ZrP2O7 bonded Si3N4 porous structure is formed; the other is at temperatures above 250 °C, at which solid state sintering of the ZrP2O7 dominates and a continuous open porosity network is obtained. The effect of the ZrP2O7 binder content on sintering behavior, porosity and mechanical properties is also investigated.