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

Air-sintered and atmospherically reduced BaTiO3 ceramics were fluorinated b y the introduction of a CF3CH2OH fluorination agent into a hot furnace usin g a supporting gas: either pure nitrogen or nitrogen containing a low conce ntration of oxygen. The nitrogen-supported fluorination resulted in a decre ase in the resistivity of the insulating air-sintered samples to semiconduc ting values, primarily due to atmospheric reduction. When air-sintered samp les 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 degreesC) resulted in a decrease of thei r resistivity and a remarkable PTCR effect. (C) 2001 Elsevier Science Ltd. All rights reserved.