A direct foaming method of dispersed suspensions containing muscovite particulates and a glass powder (47BaO-21B(2)O(3)-27SiO(2)-5Al(2)O(3). in mol%) is used to prepare porous ceramic structures. The sintered foams exhibit extremely low thermal conductivity and slight expansion during the thermal treatment at 1000 degrees C. Both the foam stability and its thermal conductivity are investigated by considering foaming agents, muscovite/glass ratios, solid contents, microwave drying, wetting behaviors, and foam consolidation. One of the muscovite/glass ceramic foam, thermally treated at 950 degrees C for 1 h, showed the lowest thermal conductivity of 0.18 W m(-1) K (1) at 800 degrees C among all of the prepared samples. Its gas permeability and compressive strength are 0.1 x 10(-7) cm(2) and 440 kPa, respectively. (C) 2011 Elsevier B.V. All rights reserved.