The influence of Mn addition on the Positive Temperature Coefficient (PTC) effect of BaTiO3 ceramic semiconductors is investigated in this report. Mn free and Mn doped specimens were sintered at 1350°C for 1h in air. Mn addition significantly promoted the magnitude of the PTC effect. The activation energy was evaluated from Arrhenius plots of electrical conductivity. The trap densities of the grain boundaries above and below the Curie temperature, Tc, were estimated from the activation energy, permittivity, and mean radius of the grains. Addition of Mn increased the difference between the trap densities above and below Tc. SEM observation of the fractured surface of the specimens revealed the points to be analyzed which correspond to the grain boundaries, and AES spectra were obtained on these analysis points. As a result, no Mn was found at the grain boundaries. It appears that the Mn elements which dissolves in the grains increases the change of the trap density of the grain boundaries at Tc, and this could be one of the causes which promotes the magnitude of the PTC.
