Stufy of the defect profile and electrical properties of Nb and La-doped BaTiO3

The aim of this work is to study the impact of two different and typical donor-dopants; Nb2O5 and La2O3' on the electrical properties of BaTiO3. Besides, the influence of Nb-5- and La3+ on the charge compensation mechanism was evaluated. On this way, it was determined that, the defect structure is not only affected by the dopant ion but also by its concentration. Amount of dopant also affects the electrical properties of BaTiO3 ceramics. In fact, for low Nb2O5 or La2O3 concentration, electronic compensation prevails, leading to a low - resistive material with an important PTCR effect. By EPR an increases in the oxygen vacancies with a low lanthanum addition was determined. This phenomenon could be associated to the lanthanum acceptor behavior. On the other hand, high dopant concentration leads to a high - resistive material showing GBBL characteristics. In this case, a high content of double - ionized barium vacancies able to trap electrons, and a thin glassy - phase film covering the BaTiO3 grains lead to a high - resistive material. This phenomenon encourages the hypothesis in which barium vacancies act as acceptor centers at the grain boundaries in BaTiO3 ceramics.