Institute de Ciencia de Materiales de Aragón, Consejo Superior de Investigaciones Científicas-Universidad de Zaragoza, 50009, Zaragoza, Spain
Abstract:
The results of the impedance spectroscopy measurements on eutectic samples based on zirconium oxide are presented here. Samples of CaZrO3---ZrO2(cubic) and MgO---ZrO2(cubic) have been grown by a directional solidification procedure such that the different phases appear nearly oriented along the growth direction (lamellae in the system of CaZrO3-ZrO2(cubic) and fibers of MgO in a ZrO2 matrix in the other system). The DC electrical conductivity has been measured by impedance spectroscopy along and across the growth axis. For CaZrO3---ZrO2 the coductivity is clearly anisotropic. The following values for σT have been obtained: the conductivity at 600 °C equals 2.0 × 10?6 Ω?1 cm?1 perpendicular to the fiber axis and 1.4 × 10?5 Ω?1 cm?1 parallel to it and with an activation energy of 1.3 eV for σT. For MgO---ZrO2(cubic) the isotropic value of the conductivity at 600 °C is 10?4 Ω?1cm?1 with activation energy for σT of 1.5 eV. The anisotropic conductivity in the CaZrO3---ZrO2 (cubic) system has been explained by a model of an ordered stacking of oxygen conducting (cubic ZrO2) and non-conducting (CaZrO3 or MgO) phases.