The PTCR (positive temperature coefficient resistivity) effect of BaTiO3 based semiconducting ceramics is usually to the donor or acceptor dopants. In would be influenced severely by vapor dopants during sintering. With high vapor pressure at high temperature, CdO could be employed as a suitable vapor dopant. The influence of CdO and CdO vapor on the PTCR effect of BaTiO3 based semiconducting ceramics was studied. It was found for the first fime that either solid CdO or CdO vapor dopant could enhance the PTCR effect of BaTiO3 based semiconducting ceramics. The enhancement caused by CdO vapor dopant was much more obvious than the caused by solid CdO dopant. This phenomenon could not be interpreted by the existing theory. From a view of defect chemistry, it was presumed that the enhancement effect were due to the transversion of the Cd^2+ at grainboundary from Ba sites to Ti sites during ferroelectric phase transition.

Key words: CADMIUM OXIDE, DOPE, CERAMICS, POSITIVE TEMPERATURE COEFFICIENT, THERMISTOR