Resistivity Enhancement and Transport Mechanisms in (1-x)BaTiO3-xBi(Zn1/2Ti1/2)O3 and (1-x)SrTiO3-xBi(Zn1/2Ti1/2)O3

Ceramics of composition (1-x)BaTiO3-xBi(Zn1/2Ti1/2)O-3 (BT-BZT) were prepared by solid-state synthesis; they have been shown to exhibit excellent properties suited for high-temperature dielectric applications. The X-ray diffraction data showed a single-phase perovskite structure for all the compositions prepared (x0.1 BZT). The compositions with less than 0.075 BZT exhibited tetragonal symmetry at room temperature and pseudo-cubic symmetry above it. Most notably, a significant improvement in insulation properties was measured with the addition of BZT. Both low-field AC impedance and high-field direct DC measurements indicated an increase in resistivity of at least two orders of magnitude at 400 degrees C with the addition of just 0.03 BZT (similar to 10(7)-cm) into the solid solution as compared to pure BT (similar to 10(5)-cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic for 0.075 BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT-BZT, but could also be observed in the paraelectric SrTiO3-BZT system.