Dielectric percolation and solid-state reaction of the CaCu_3Ti_4O_(12)-ZnNb_2O_6 composite materials

By chosing ZnNb2O6 with lower permittivity as matrix and CaCu3Ti4O12 with higher permittivity as reinforcement, the dielectric percolation behaviour and solid-state reaction under high sintering temperature of the CaCu3Ti4O12-ZnNb2O6 composites were studied. The results show that dielectric percolation behaviour can be observed and the relative permittivity suddenly transits to 5 600 when the volume fraction of CaCu3Ti4O12 is over 51.0%. The solid-state reactions between CaCu3Ti4O12 and ZnNb2O6 occur at 900 ℃ above and form Cu0.5Ti0.5NbO4, CaNb2O6, Zn2TiO4 and an unknown substance. This substance has a set of X-ray diffraction peaks which is similar to that of CaCu3Ti4O12 and its lattice constant is a litter greater than that of CaCu3Ti4O12. It is believed to be a solid solution of CaCu3Ti4O12 formed by the partial substitution of Nb5+ for Ti4+ in CaCu3Ti4O12.