THE ENHANCED PENETRATION OF OXYGEN ALONG THE GRAIN-BOUNDARY IN SEMICONDUCTING BARIUM-TITANATE

The characteristics of Positive Temperature Coefficient of Resistivity (PTCR) thermistors depend strongly on the atmosphere, especially oxygen, during the fabrication process. The PTCR jump decreases when the sample is heated in a reducing atmosphere, while it increases when the sample is heated in air. The behavior of oxygen which is important to improve the PTCR jump has been examined by a tracer (O-18) method. The depth profile of the tracer has been determined by means of Secondary ion mass spectrometry (SIMS). The rate of penetration of oxygen into the grain boundary is very rapid and the PTCR jump depends on the amount of the oxygen penetrated into such a region.