Analysis of secondary phases segregated and precipitated in SnO2-based varistors

R PARRA,; M.S. CASTRO; J.A. VARELA

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY

Elsevier

Año: 2005 vol. 25 p. 401 - 406

0955-2219

Transmission and scanning electron microscopy techniques were used to study the heterogeneities found in the microstructure of SnO2.Co3O4.Nb2O5.Fe2O3 and SnO2.ZnO.Nb2O5.Fe2O3 varistors. Second phases encountered both inside the grains and in grain boundary regions were identified using energy dispersive spectrometry and electron diffraction patterns. Through the electrical characterisation, the presence of iron oxide among the additives was determined to highlight the nonlinear properties of the specimens. A discussion on the influence of second phases on the nonlinear features of these systems is also addressed.