Effect of cesium substitution on the thermal evolution and ceramics formation of potassium-based geopolymer

The thermal evolution of cesium-substituted potassium-based geopolymer ((K_1-xCs_x)₂O·Al₂O ₃·5SiO₂·11H₂O, x = 0, 0.1, 0.2, 0.3, and 0.4) on heating is studied by a variety of techniques. Phase compositions and thermal expansion behaviors of the ceramics derived from the geopolymer are characterized. All of the geopolymer specimens with or without cesium substitution exhibit similar thermal evolution trends. Major weight losses before 600 °C from all the geopolymer specimens are observed and are resulted from evaporation of free water and hydroxyl groups. Thermal shrinkage of these specimens can be divided into four stages, i.e. structural resilience, dehydration, dehydroxylation and sintering, according to the dilatometer results. For these specimens, significant difference is observed in the viscous sintering stage and the effect of cesium is to reduce the thermal shrinkage in this stage due to the increased matrix viscosity. In the ceramics derived from geopolymer, the amount of stabilized leucite increases with the amount of cesium and with 20% cesium substitution leucite is fully stabilized in cubic phase.