Effect of Firing Atmosphere on Electrical Properties of Gd-Fe-Codoped Barium Titanate Ceramics Added with B<sub>2</sub>O<sub>3</sub>

Effect of firing atmosphere on the electrical properties of Gd-Fe-codoped BaTiO3 ceramics added with B2O3 was studied by measuring their electrical resistivity, diffuse reflectance spectra and electron spin resonance (ESR) spectroscopy. The bulk density of the samples fired above 1300°C, except Fe-doped samples fired in air, was as high as 94% of the theoretical value. Semiconducting BaTiO3 was obtained in the case of Fe-doped and un-doped samples fired in Ar at all range of firing temperature. The room temperature resistivity of the samples fired in Ar was lowered with increase in firing temperature. It was considered that the lowering of the resistivity was due to the grain growth with rise of temperature. The PTCR jump for Fe-doped samples fired in Ar was much larger in all range of firing temperature than that for Fe-undoped samples fired in Ar. This result indicated that Fe ions segregated in the grain boundary and acted as an acceptor.