Positive temperature coefficient of resistivity in Pb(Fe1/2Nb1/2)O3 ceramics

The positive temperature coefficient of resistivity (PTCR) effect in ferroelectric Pb(Fe1/2Nb1/2)O3 (PFN) ceramics was examined to determine its physical meaning as the evidence of the ferroelectric domain structure. Monitoring of the temperature dependence of resistivity showed that its PTCR effect begins around the dielectric maximum temperature (Tm). The existence of the space charge region near the grain boundary was verified via impedance spectroscopy, and X-ray photoelectron spectroscopy (XPS) indicated it to be due to Pb volatilization during the sintering process. In addition, well-development ferroelectric domain structure, which was expected to be found according to Jonkerʹs theory, was observed with transmission electron microscopy (TEM).