The influence of aluminium on the overall properties of SnO2-based varistors
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The influence of aluminium on the development of the microstructure and on the electrical behaviour of the SnO2 · Co3O4 · Nb2O5 typical varistor system was studied. Two sources of Al were used, alumina (Al2O3) and boehmite (AlO(OH)). The microstructural features were characterised with scanning (SEM) and transmission (TEM) electron microscopies. The different phases present in the studied samples were also studied with XRD, EDS and electron diffraction patterns of selected areas (SAED). Particles containing Sn, Co, Al, and O were unveiled with TEM. Impedance spectroscopy measurements and current density versus electric field characteristics revealed superior electrical properties for samples with AlO(OH). The higher non-linearity (α = 19) was achieved with the addition of 0.1% mol of boehmite. The influence of the secondary phases on the electrical properties is also addressed in this work.
KeywordsSnO2 Oxygen Vacancy Co3O4 Nb2O5 Unit Cell Volume
The authors are grateful to the Programa CYTED (Proyecto PROALERTA), to CONICET (Argentina), to CNPq and FAPESP (Brazil) for the financial support provided for this research. The collaboration of Dr. Alberto Scian at the CETMIC in La Plata is also acknowledged.
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