Electrical transport in low-lead (1-x)BaTiO₃-xPbMg_1/3Nb_2/3O₃ ceramics

Low-lead (1-x)BaTiO₃-xPbMg_1/3Nb_2/3O₃ ceramics (x = 0, 0.025, 0.05, 0.075, 0.1, and 0.15) were prepared by the conventional oxide mixed sintering process, and their optical band gap, Seebeck coefficient, ac ( ${\sigma }_{\text{ac}}$) and dc ( ${\sigma }_{\text{dc}}$) conductivities as a function of temperature were investigated for the first time. It was found that all samples have p-type conductivity. The low-frequency (20 Hz-2 MHz) ac conductivity obeys a power law ${\sigma }_{\text{ac}}~{\omega }^s$, which is characteristic for disordered materials. The frequency exponent s is a decreasing function of temperature and tends to zero at high temperature. ${\sigma }_{\text{ac}}$ is proportional to ${\omega }^{0.07}$ - ${\omega }^{0.31}$ in the low-frequency region and to ${\omega }^{0.51}$ - ${\omega }^{0.98}$ in the high-temperature region. The temperature dependence of the dc conductivity showed a change in slope around the temperature at which the phase transition appeared. Both ac and dc conductivities showed a thermally activated character and possessed linear parts with different activation energies and some irregular changes. It was found that the hopping charge carriers dominate at low temperature and small polarons and oxygen vacancies dominate at higher temperature. (1-x)BaTiO₃-xPbMg_1/3Nb_2/3O₃ ceramics are expected to be promising new candidate for low-lead electronic materials.