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1、JournalofTheElectrochemicalSociety,148~3!E121-E126~2001!E1210013-4651/2001/148~3!/E121/6/$7.00©TheElectrochemicalSociety,Inc.GrainBoundaryBlockingEffectinZirconia:ASchottkyBarrierAnalysisX.GuoandJ.Maier*Max-Planck-InstitutfuÈrFestkoÈrperforschung,70569Stuttgart,G
2、ermanyThegrainboundaryelectricalpropertiesofhighpurityZrO2ceramicmaterialsdopedwith2,3,and8mol%Y2O3,and8mol%Y2O3co-dopedwith0.4mol%Al2O3werestudiedinthetemperaturerangeof200to500°Cbyelectrochemicaltechniquesandweretheoreticallyanalyzed.Althoughthepresenceofasilic
3、eousphaseisshowntobeamajorcauseforthegrainboundaryblockingeffect,thegrainboundarypropertiesappeartobesigni®cantlyin¯uencedbyspacecharges,particularlyinmaterialsofhighpurity.Theoxygenvacancydistributionandthegrainboundaryresistivitywerecalculatedfor8mol%Y2O3dopedZ
4、rO2byassumingdoubleSchottkybarriers,andtheresultswerecomparedwiththeexperiment.Itisshownthatreasonablespacechargepotentialsleadtograinboundaryeffectswhichareconsistentwiththeexperimentalfeatures.Incontrarytothebulkinwhichdefectassociatesprevail~attemperatures,560
5、°C!,intheboundaryregions,associationeffectscanbeassumedtobemuchlesspronouncedduetothevacancydepletion.©2001TheElectrochemicalSociety.@DOI:10.1149/1.1348267#Allrightsreserved.ManuscriptsubmittedAugust7,2000;revisedmanuscriptreceivedDecember4,2000.ZrO2~usuallydoped
6、withY2O3,CaO,orMgO!isatpresentthe1.Theactualspacechargethicknessislargerthanthecalculatedmostimportantsolidelectrolyte,owingtoitsapplicationsintech-Debyelength.Indeedgrainboundarythicknessesdeterminedfromnologicallyimportantdevices,e.g.,oxygensensors~l-probes!and
7、impedancespectroscopywerereportedtobeintherangeof1.5to6.7nm,4,28dependingongrainsize,concentrationanddopanttype.solid-oxidefuelcells.Inmostoftheseapplications,ZrO2ispresentinpolycrystallineform,becauseofthedif®cultyandexpenseasso-Thethicknessofthedisorderedgrainb
8、oundarystructure~i.e.,thegrainboundarycore!determinedfromTEMisonlyabout0.8nm29ciatedwiththefabricationofsinglecrystals.Consequently,grainboundariesareacrucialp
