The influence of firing profile and additives on the PTCR effect and microstructure of BaTiO3 ceramics

Nonstoichiometric BaTiO₃ PTCR type materials are investigated with various amounts of MnO₂, Sb₂O₃ and MgO dopants. Specimens fired with a nonisothermal rate-controlled sintering profile exhibit a rather fine and uniform microstructure as compared to those processed by conventional sintering techniques. The temperature at which the resistivity anomaly begins is observed to decrease with Sb₂O₃ and MgO contents. The Curie point of BaTiO₃-based ceramics can be altered by addition of Sb₂O₃, and the dielectric peak is maintained by the presence of MgO additive. Magnesium ions act as acceptors in the BaTiO₂ lattice, while antimony ions as donors. The presence of magnesium compensates some of the antimony, hence the doped-BaTiO₃ seminonductive region is pushed to higher contents.