Anomalous Increase in the Resistivity of n-Doped BaTiO3-Based Ceramics with Pressure Observed at Room Temperature

In this article, the observation of a large anomalous increase in room temperature resistivity with pressure following the pressure-induced ferroelectric-paraelectric phase transition in n-doped BaTiO3-based ceramics is reported. It is well known that the thermally induced phase transition in these ceramics is accompanied by an anomalous rise in resistivity, an effect referred to as the positive temperature coefficient of resistance. This phenomenon is considered as a grain boundary effect which depends on the behavior of the spontaneous polarization and the relative permittivity of the material with temperature. As the pressure dependence of the relative permittivity and spontaneous polarization in pure BaTiO3 crystals resemble their corresponding behavior with temperature, it was tempting to speculate that the pressure-induced phase transition in n-doped BaTiO3-based ceramics may also be accompanied by a similar rise in resistivity. Preliminary investigations confirming such a prediction were carried out. This behavior may be, appropriately, referred to as the positive pressure coefficient of resistance. A model based on the grain boundary effects has also been proposed to explain the results. This large increase of resistivity with applied pressure may be used for pressure sensing applications.