Abstract
Room temperature (R.T.) resistivity and the positive temperature coefficient of resistivity (PTCR) of Gd-Mn codoped BaTiO3 from powders obtained by hydrothermal synthesis were investigated. Mixtures of Gd(NO3)3, Mn(NO3)2, and BaTiO3 powders (average particle size ; 0.5μm) obtained by hydrothermal synthesis were dried and pressed into pellets with a diameter of 2 cm. Then, the pellets fired at 1380°C for 2 h in 0.1%H2-Ar atmosphere and oxidized at the temperature range of 1000 to 1300°C for 1h during cooling period. Fired sample which had low R.T. resistivity and remarkable PTCR characteristics was obtained for 0.2 mol%Gd-0.075mol%Mn codoped BaTiO3 which fired at 1380°C in 0.1%H2-Ar, oxidized for 1h at 1300°C and cooled to R. T. in air. PTCR jump of the sample cooled in air was 300times higher than that of the sample cooled in 0.1%H2-Ar. This result indicated that absorbed oxygen which was introduced into grain boundary by oxidation at 1300°C, was not desorbed during cooling in air from 1300 to 1200°C.
