Phase equilibria study of K–O–Si system in equilibrium with air

The binary phase diagram in the silica rich corner of K–O–Si system in equilibrium with air has been studied at temperatures between 770 °C and 1500 °C. Equilibration at high temperature in an appropriate containment material of pure silica, followed by rapid quenching and measurement of phase structures and assemblages using SEM-EDS confirmed by an electron probe X-ray microanalysis technique, was carried out to obtain the phase composition data at equilibrium. The results are in good agreement with previous experimental data and close to the earlier assessed phase equilibria at silica saturation.