MICROSTRUCTURE AND DIELECTRIC-PROPERTIES OF SRTIO3-PBTIO3-CATIO3 CERAMICS

The electrical properties and microstructures of SrTiO3-PbTiO3-CaTiO3- Bi2O3-TiO2 systems were investigated. It was found that the materials had two inhomogeneous regions, called ''grain core-grain shell'', by h eld-emission scanning electron microscopy (FE-SEM) and transmission el ectron microscopy (TEM) observations. The dielectric constant showed t wo peaks. The dielectric constant at temperatures below 0 degrees C de creased, whereas that at temperatures above 100 degrees C increased sl ightly under DC bias field. D-E loops revealed that the ferroelectric state existed at temperatures below 0 degrees C, and the paraelectric- like state existed at temperatures above 100 degrees C. The observed f requency dependence and aging phenomena showed that this material was a relaxer. A relationship between the electrical properties and micros tructure has been proposed.