β-Conductivity Contrast at Barium Titanate Thermistor Grain Boundaries

摘要

Barium titanate based PTC thermistor materials have been examined using the conductive mode of a scanning electron microscope. Under an applied voltage bias, at temperatures above the Curie temperature, bright and dark lines which are due to β-conductivity appear coincident with grain boundaries. The mechanisms of contrast formation are discussed. Such contrast can be used to evaluate the distribution of this type of active grain boundary.