**Abstract**

More and more attention had been given to geopolymers (GPs) over the last decades because of an increasing urgency to search for high-performance and/or environment-friendly alternatives to traditional Portland cement. In addition, geopolymer technology could also provide an innovative approach to prepare advanced ceramic products by overcoming problems faced in the conventional preparation technology. With only the need to go through appropriate thermal treatment procedure, geopolymers could be directly in situ transformed into advanced ceramics such as leucite or pollucite with adjustable microstructures, mechanical properties, coefficient of thermal expansion, and melting points. In the process of high-temperature treatment, multiple parameters, such as the composition of geopolymer, treatment temperature, thermal insulation, etc., would affect the phase composition and microstructure of the resulting products. In the present chapter, two kinds of mixed-alkali metal ion-activated geopolymer systems, Cs(1-*x*)Li*x*GP (where *x* = 0, 0.1, 0.2, and 0.3) and Cs(1-*x*)Na*x*GP (where *x* = 0, 0.1, 0.2, 0.3, and 0.4), respectively, were designed and prepared. Phase composition, microstructure evolution, and thermal expansion behaviors of the ceramics derived from the geopolymers were characterized and the effects of ion substitution on the thermal evolution of geopolymer were evaluated.

**Keywords:** geopolymer, high-temperature treatment, pollucite, spodumene, amorphous glass phase, phase composition, microstructure, thermal expansion behavior
