Abstract

AGUILAR-MARTINEZ, J.A et al. Effect of CaO on the microstructure and non-ohmic properties of (Co,Sb)-doped SnO₂ varistors. Rev. mex. fis. [online]. 2008, vol.54, n.1, pp.20-24. ISSN 0035-001X.

The effect of CaO through additions of CaCO₃ on the physical characteristics, microstructure, and current-voltage properties of (Co-Sb)-doped SnO2 varistors was investigated. SnO₂-Co₃O₄-Sb₂O₅ ceramics with additions of 0.1, 0.5 and 1 mol % CaO were sintered at 1450°C under oxidizing atmosphere and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Results show that, at low and intermediate CaO levels, density is not significantly influenced, whilst at the highest level, density decreases substantially. The nonlinear coefficient and the breakdown voltage behave similarly in one sense because both present a maximum, and because at the highest CaO level, both response variables show the lowest values. The nonlinear coefficient presents a maximum of 12.9 at 0.1 mol % CaO, while the same maximum for the breakdown voltage occurs at 0.5 mol % CaO. At 1 mol % CaO, the breakdown voltage is 288 Vcm^-1.

Keywords : Varistors; breakdown voltage; nonlinearity.

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