Diffusion effects of alumina on microstructures and positive temperature coefficient resistivity (PTCR) characteristics of barium-strontium titanate ceramics

The effects of alumina diffusion on microstructures and positive temperature coefficient resistivity (PTCR) characteristics of barium-strontium titanate (BST) ceramics were investigated. The diffusion effects of alumina were found only when the sintering temperature was as high as 1400°C. The diffusion leads to an increase in grain size and formation of a liquid phase containing alumina, silicon and excess titanium. It was observed that surrounding alumina in the sintering of the BST ceramics leads to the diffusion of alumina into the grain boundaries.