A method for the formation of intergranular crystalline phases in liquid phase sintering

Abstract

During the liquid phase sintering process a liquid is formed, penetrates into the pores, causes rearrangement of particles and shrinkage and forms an amorphous and/or crystalline intergranular phase after firing which re-melts upon heating to the same sintering temperature. In this research a method is proposed to alter the intergranular phase to a phase with a melting point higher than the sintering temperature. The hypothesis is based on the shape of the phase diagram and precise control of particle sizes of liquid forming species. Results show that in the CaO–Al2O3 system a liquid is formed at 1 500 °C and it will then change to CaO. Al2O3 with a melting point of more than 1 600 °C. Differential scanning calorimetry analysis shows that the processes of formation of liquid and crystallization of concomitant crystalline phases occur obviously separately in this system. The system CaO–TiO2 also confirms the hypothesis, although more analytical evidence is needed for the latter.