Fabrication of Lead-Free Semiconducting Ceramics Using BaTiO3-(Bi1/2Na1/2)TiO3 System by Sintering in Air Atmosphere
BaTiO3–(Bi1/2Na1/2)TiO3 (abbreviated as BT-BNT) solid solution ceramics, as a lead-free PTC (Positive Temperature Coefficient of resistivity) thermistor material usable over 130°C, were synthesized in air atmosphere. By conventional processes, La-doping was not effective in giving semiconducting property to the BT-BNT ceramics because of volatilization of sodium and bismuth during sintering. By preventing the volatilization by lowering the sintering temperature using very fine TiO2 powder and by adding calcium oxide to calcined BT-BNT powders, we obtained BT-BNT semiconducting ceramics which shows a resistivity change near Curie temperature.
Chazono Hirokazu, Fujihara Shinobu, Katayama Keiichi, Masumoto Hiroshi, Mizoguchi Teruyasu, Osada Minoru, Shinozaki Kazuo and Takeda Hiroaki
T. Tateishi et al., "Fabrication of Lead-Free Semiconducting Ceramics Using BaTiO3-(Bi1/2Na1/2)TiO3 System by Sintering in Air Atmosphere", Key Engineering Materials, Vol. 485, pp. 245-248, 2011