This paper reported the hydrothermal synthesis and thermal behavior of a novel kind of dawsonite-type solid solution K1-x(NH4)(x)Al(OH)(2)CO3 (x=0.2-0.93). The effects of NH4+/K+ molar ratio in the starting reactants and the hydrothermal reaction time on the composition of K1-x(NH4)(x)Al(OH)(2)CO3 Were investigated. In addition, the influence of the composition on the thermal stability of the solid solution was studied by DTA/TG analyses. It was indicated that compound K-0.44(NH4)(0.56)Al(OH)(2)CO3 (x = 0.56) is the most thermally stable one among all the dawsonite type solid solutions. Furthermore, K-beta-Al2O3, a solid state K+ ion conductor was prepared by calcining K-0.19(NH4)(0.81)Al(OH)(2)CO3 at 1250 degrees C. (c) 2005 Elsevier B.V. All rights reserved.