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Effects of Pr2O3 on the nonlinear electrical characteristics and dielectric properties of SnO2·Co2O3·Ta2O5 varistor systems

“…This phenomenon is also reported by Bacelar and Oliveira [13]. Since any new phase precipitation in the grain boundary is not detected, the two barrier tops should touch each other, which is confirmed by Bacelar et al and Bueno et al [13,14]. The positive charges ðSn $$$$ i ; V $$ O ; Ta $ Sn Þ extending from both the sides of the grain boundary are compensated by the negative charges (Sn 00 Sn , V 0000 Sn , e 0 , Co 00 Sn , Pr 0 Sn ) at the grain boundary interface.…”

“…As can be seen, no notable intergranular insulating layer separates two SnO 2 grains was observed by SEM, which is distinct from the ZnO varistor. This phenomenon is also reported by Bacelar and Oliveira [13]. Since any new phase precipitation in the grain boundary is not detected, the two barrier tops should touch each other, which is confirmed by Bacelar et al and Bueno et al [13,14].…”

How Cr2O3 influences the microstructure and nonohmic features of the SnO2(Cox, Mn1−x)O-based varistor system

“…6 In fact, the SnO 2 -based varistor can be obtained by adding densifying dopants, such as CoO, MnO and ZnO 16 in amounts exceeding 0.5 mol%. [17][18][19][20][21] It is believed that such oxide dopants facilitate mass transport throughout the grain boundary region, increasing densification of the polycrystalline matrix. 18,19 It should be noted that the most widely studied densifying dopant used in SnO 2 -based varistor systems is CoO.…”

Low voltage varistor ceramics based on SnO2

“…Co segregation at grain boundary is reported with the help of EDX, TEM and impedance analysis (Wang et al 2000;Bacelar et al 2002;Cassia et al 2005). The incorporation of either antimony oxide or niobium oxide increases electronic conductivity of tin oxide.…”