Fabrication of lead-free and high Tc BaTiO3-based thermistor ceramics using deoxidizing effect of oxygen-containing α-zirconium

Oxygen-containing α-zirconium (α-ZrOx) has been synthesized by an arc melting method. The oxidation of the α-ZrOx powders occurs at 480 °C in air. After this oxidation, the reaction product is normal zirconia ZrO2 powders. We demonstrate an application of this oxidation process. By firing green bodies of BaTiO3–(Bi1/2Na1/2)TiO3 solid-solution ceramics in contact with the α-ZrOx powders, the ceramics acquire a semiconductivity with a positive temperature coefficient of resistivity (PTC) behavior. We propose a method to prepare lead-free PTC thermistor ceramics with a Curie temperature Tc over 130 °C, which is that of BaTiO3, in air.