Microstructure and electric properties of a SnO2 based varistor

High non-linear J x E electrical characteristic (alpha=41) were obtained in the Nb2O5 and Cr2O3 doped CoO highly densified SnO2 ceramics. X-ray diffra ction analysis showed that these ceramics are apparently single phase. Elec trical properties and microstructure are highly dependent on the Cr2O3 conc entration and on the sintering temperature. Excess of Cr2O3 leads to porous ceramics destroying the material's electrical characteristics probably due to precipitation of second phase of CoCr2O4 Dopant segregation and/or soli d solution formation at the grain boundaries can be responsible for the for mation of the electrical barriers which originate the varistor behaviour. ( C) 1998 Elsevier Science Limited and Techna S.r.l. All rights reserved.