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Ferroelectric and piezoelectric properties of tungsten doped CaBi4Ti4O15 ceramics

JElectroceram(2008)21:305–308DOI10.1007/s10832-007-9144-0

FerroelectricandpiezoelectricpropertiesoftungstendopedCaBi4Ti4O15ceramics

JiangtaoZeng&YingWang&YongxiangLi&QunbaoYang&QingruiYin

Published#online:2May2007

SpringerScience+BusinessMedia,LLC2007

AbstractTungstendopedCaBi4Ti4O15(CBT)ceramicswaspreparedbysolid-statereactionmethod.Apuresinglephaseoflayer-structuredferroelectricwithm=4wasformedwhenx≤0.025.TheeffectofWdopingondielec-tric,ferroelectricandpiezoelectricpropertieswasinvesti-gated.W6+dopingincreasedthetemperaturestabilityofdielectricconstantanddecreaseddielectricloss.W6+dopingdecreasedtheremanentpolarization,whilethecoercivefielddecreasedaswell,asaresult,thepiezoelectricconstantwasincreased.ACconductivitymeasurementshowedthatW6+dopingincreasedtheconductivityofCBTceramicsandshowedn-typeconductingmechanism.W6+dopedceramicshassmalleractivationenergyduetomanydefectsintro-ducedinthecrystallattice.

KeywordsBismuthlayer-structuredferroelectric.Tungstendopant.Lead-freepiezoelectric

1Introduction

Bismuthlayer-structuredferroelectrics(BLSFs)areexten-sivelystudiedforitspotentialuseinnon-volatilememory.Theyarealsogoodcandidateforhightemperaturepiezo-electricapplicationsduetotheirhighCurietemperature.BLSFscompoundshavethegeneralformulaof(Bi2O2)2+(Am 1BmO3m+1)2 ,whereA-sitecanbeoccupiedbyava-rietyofmono-,di-ortrivalentionswithalargeionicradius,

J.ZengY.WangY.Li(*)Q.YangQ.Yin

TheStateKeyLaboratoryofHighPerformanceCeramicsandSuperfineMicrostructure,ShanghaiInstituteofCeramics,ChineseAcademyofSciences,

Shanghai200050,People’sRepublicofChinae-mail:yxli@http://doc.xuehai.net

andBdenotestetra-orpentavalentionswithasmallionicradius.Theintegermrangesfrom2to5[1,2].Bi4Ti3O12(BIT)isoneofthemoststudiedcompoundsamongBLSFs[3,4].DuringthesinteringofBITceramicathightem-perature,Bi2O3showsavolatilenature.Therefore,oxygenvacanciesareformedinpureBIT,whichresultinap-typeconductor[5].DonordopantssuchasV5+,W6+inBITcandecreasetheconductivityandenhancetheferroelectricandpiezoelectricproperties[6–9].Nb5+andW6+dopedBITceramicsincreasedthepiezoelectricconstantd33toashighas20pC/N[9,10].CaBi4Ti4O15(CBT)isaverypromisingcandidateforhightemperaturepiezoelectricapplicationsduetoitshighCurietemperature(790°C)andhighelectricalresistance.IthasaverysimilarcrystalstructuretoBIT.A-sitedopingisusuallyusedtoenhancethepiezoelectricpropertiesofCBT,butA-sitedopingoftencausesadecreaseofCurietemperature[11,12].B-sitedopinginCBThasrarelybeenstudied.Itisstillunknownwhetherdonordopantcandecreasetheoxygenvacanciesandconductivity.Inthispaper,theeffectsofW6+dopantonthedielectric,ferroelectricandpiezoelectricpropertiesofCBTarestudied.

2Experimental

CaBi4Ti4 xWxO15(x=0,0.025,0.050,0.075)(CBTWwerepreparedbythesolid-statereactionmethod.x)ceramicsThestartingrawmaterialswereanalyticalpuritygradeoxidesandcarbonatepowders:Bi2O3,TiO2,WO3,andCaCO3.Chemicalstoichiometricamountsofthestartingpowderswerethoroughlymixedwithethanolinaballmillfor4h,driedandcalcinedat900°Cfor3hinanaluminacrucible.Aftercalcination,thegroundandball-milledpowderswerepressedintodisksof15mmindiameterandabout2mminthickness.Thepressedsampleswere

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