Calcium tungsten bronzes CaxWO3 (0.01 <= x <= 0.15) were synthesized by hybrid microwave method from mixtures of CaO, WO3 and tungsten powder. Single-phased samples can be obtained by microwave heating within 40 min. With the increase of calcium content, the crystal structure of CaxWO3 transforms from orthorhombic (0.01 <= x <= 0.02) to tetragonal (0.03 <= x <= 0.11) and then to cubic (0.12 <= x <= 0.15). The average size of crystallites is in the range 1-5 mu m. All samples show semiconductor behaviour in their temperature dependence of resistivity. The electrical conduction mechanism changes from variable-range hopping to the thermally activated mechanism when x > 0.12. (c) 2005 Elsevier Ltd. All rights reserved.