We investigated the solid-state reactions between CaCu3Ti4O12 and ZnNb2O6 oxides with a molar ratio of 1:1 in air at temperatures from 600 to 1000 degrees C. Solid-state reactions between CaCu3Ti4O12 and ZnNb2O6 occurred readily around 900 degrees C and above. The reaction products were Cu0.5Ti0.5NbO4, CaNb2O6, and Zn2TiO4 (and/or ZnCuTiO4). A substance having a set of X-ray diffraction peaks similar to that of CaCu3Ti4O12 was observed, and it is believed to be a solid solution of CaCu3Ti4O12 formed by the partial substitution of Nb5+ for Ti4+ ions. The lattice constant of this solid solution is greater than that of CaCu3Ti4O12. The reaction behaviors of CaCu3Ti4O12-Nb2O5 system were also studied in order to better understand the reactions of the CaCu3Ti4O12-ZnNb2O6 system. In addition to the formation of solid solution between CaCu3Ti4O12 and Nb2O5, solid-state reactions between CaCu3Ti4O12 and Nb2O5 also occurred simultaneously. (C) 2007 Elsevier Ltd. All rights reserved.