Rigid, mechanically reinforced, composite Ag+-ion conductors based on xAgI center dot(100-x) (0.67Ag(2)O center dot 0.33B(2)O(3)), 40 <= x <= 60, glasses and hard insulating powders of alpha-Al2O3 (2 mu m) or ZrO2 (1 mu m) were prepared by a high-pressure method. Microstructure of the composites, depended on the content of AgI in the glasses and the temperature of the high-pressure stage of the synthesis. In all cases, however, it consisted of the evenly distributed phases (conductive and insulating), which did not interpenetrate at a narrometer length scale. It was found that the high electrical conductivity of the composites, though somewhat lower than that of the glasses, generally followed the temperature- and composition dependencies of the latter. An important advantage of the composites over the corresponding glasses was their higher microhardness and non-brittleness, which, contrary to the glasses, enabled their post-synthesis machining, cutting or polishing. (c) 2008 Elsevier B. V. All rights reserved.