部分酸化Ti粉添加によるBaTiO_3基セラミックス真空焼結体におけるPTCR特性の発現 Development of PTCR Characteristic in Vacuum-Sintered BaTiO_3-Based Ceramics by Addition of Partially Oxidized Ti Powder
The compact of the mixture composed of (Ba, Sr)TiO<SUB>3</SUB> ceramics powder and partially oxidized Ti powder (5.0mass% O) which was named TiO<SUB>2</SUB>(Ti) powder was found to show PTCR characteristic, when the compact was sintered in vacuum at 1623 K for 3.6 ks, and then heated in air at 853 K for 0.3 ks. Some properties of the sintered compacts were investigated.<BR>The results obtained were as follows; (1)Obvious PTCR characteristic developed at TiO<SUB>2</SUB>(Ti) contents of 5-7vol%. (2)The transformation from tetragonal structure (ferroelectric phase) to cubic structure (paraelectric phase) of (Ba, Sr)TiO<SUB>3</SUB> phase in the sintered and then annealed compact was suggested to occur only near the grain boundary and surface of the (Ba, Sr)TiO<SUB>3</SUB> grains. (3)The dielectric constant ratio of ε<SUB> ?? .540K</SUB>/ε<SUB> ?? t</SUB> was 1/8, which was below the value (1/3) of (Ba, Sr)TiO<SUB>3</SUB> air-sintered compact without TiO<SUB>2</SUB>(Ti), (4)The oxygen content of (Ba, Sr)TiO<SUB>3</SUB> phase fairly decreased with increasing TiO<SUB>2</SUB>(Ti) content. (5)The densification and grain growth of the compact with 5-7vol% TiO<SUB>2</SUB>(Ti) hardly occured by the sintering. (6)The mechanism for the development of PTCR characteristic by the addition of TiO<SUB>2</SUB>(Ti) was discussed, based on Heywang-Jonker's model.
粉体および粉末冶金 46(4), 348-357, 1999-04-15
Japan Society of Powder and Powder Metallurgy