The present work studied the influence of thermal treatment in oxygen rich

atmosphere on heterogeneous junctions in Mn-doped SnO2 polycrystalline system

presenting varistor behaviour. The samples were prepared by conventional oxide

mixture methodology, and were submitted to heat treatment in an oxygen-rich

atmosphere at 900C for 2h. The samples were characterized by X-ray diffraction,

scanning electron microscopy, dc and ac electrical measurements. The results

showed that there was an evident relationship between the microstructure

heterogeneity and non-ohmic electrical properties. It was found that for this

SnO2·MnO-based varistor system the heat treatment in oxygen rich atmosphere

does not necessarily increase the varistors' properties, which was related to the

decrease in the grain boundary resistance. The results were compared with Codoped

SnO2 varistors and ZnO based varistors.

Influence of Thermal Annealing Treatment in Oxygen Atmosphere on Grain

Boundary Chemistry and Non-Ohmic Properties of SnO2·MnO Polycrystalline

Semiconductors. M.O.Orlandi, P.R.Bueno, E.Longo: 2008, Physica Status Solidi

A, 2008, 205[2], 383-8