Electrical properties of undoped BaTiO3 ceramics annealed in a fluorine containing atmosphere

Air-sintered and atmospherically reduced BaTiO3 ceramics were fluorinated by the introduction of a CF3CH2OH fluorination agent into a hot furnace using a supporting gas: either pure nitrogen or nitrogen containing a low concentration of oxygen. The nitrogen-supported fluorination resulted in a decrease in the resistivity of the insulating air-sintered samples to semiconducting values, primarily due to atmospheric reduction. When air-sintered samples were fluorinated using oxygen-containing nitrogen as the supporting gas, their resistivity remained very high. The exposure of fluorinated samples to air at high temperatures (1200°C) resulted in a decrease of their resistivity and a remarkable PTCR effect.