High temperature poling effects on conducting barium titanate ceramics

A high temperature NTC resistivity transition (T c2) near 600°C has been found in donor modified barium titanate (BaTiO3). Thermal treatment around this temperature regime plus applied voltage (T c2-Poling) on previously developed PTCR materials significantly affects both electrical behavior and ferroelectric domain structure in samples which have not been annealed after sintering. This type poling results in alignment of the domain structure in a coherent nature in direction of the applied voltage. Samples with a highly suppressed resistivity transition have been developed within direction of the applied voltage, while typical PTCR behavior exists in the anti-poled direction. Properties are dependent on domain structure orientation and grain boundary coherency developed during T c2-poling. Annealed samples are not affected in the same fashion and do not show enhanced domain alignment due to inhomogeneous grain boundaries which pin the domain structure. Results indicate that conductivity and PTCR behavior is notably dependent on grain boundary and domain structure coherency. Conversion from typical PTCR behavior to one which exhibits minimal dependence on the phase transition and results in a highly conductive cubic state is described in terms of grain boundary/domain alignment.