Influence of Nb5+ and Sb3+ dopants on the defect profile, PTCR effect and GBBL characteristics of BaTiO3 ceramics

In this work, a study of the electrical properties and defect structure of PTCR (positive temperature coefficient of resistance) and GBBL (grain boundary barrier layer) BaTiO3-based ceramics was performed. For this study, different concentrations of Nb5+ or Sb3+ were employed for doping BaTiO3. Based on the Heywang-Jonker model for PTCR materials, the density of acceptor states and the potential barrier height were calculated. Doping BaTiO3 with small amounts of Nb2O5 led to higher potential barriers than those in Sb2O3-doped ceramics. From EPR analyses performed on the complete set of samples, para-magnetic defects were investigated. Hence, a relationship between the defect profile developed in the BaTiO3 materials and the transition from a low resistivity to a high resistivity material was established. From this study, an increase in the titanium vacancies relative concentration along with an increment in the electrical resistivity measured at room temperature as the dopant content increases was confirmed. (C) 2003 Elsevier Ltd. All rights reserved.