The role of oxygen vacancies on the microstructure development and on the electrical properties of SnO2–based varistors

R. PARRA; C.M. ALDAO; J.A. VARELA; M.S. CASTRO

Journal of Electroceramics

Año: 2005 vol. 14 p. 149 - 156

1385-3449

Variations on the microstructure development and on the electrical properties of SnO2-based varistors are discussed on the basis of the oxygen vacancies created or annihilated by the presence of different additives. EPR analysis of sintered samples evidenced the increase in the concentration of paramagnetic oxygen vacancies concentration when Nb2O5 is added to a SnO2.Co3O4 varistor system, as well as the diminution when Fe2O3 is included within the additives with the subsequent increase in the sample resistivity. These findings are supported by SEM analysis, density measurements and J-F curves. The characterisation of secondary phases and the main parameters describing the electrical behaviour of the studied devices are also reported in this work.