Random field in relaxor ferroelectric.pdf

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1、ReviewJournalofAdvancedDielectricsVol.2,No.2(2012)1241001(13pages)©WorldScienti¯cPublishingCompanyDOI:10.1142/S2010135X12410019RANDOMFIELDSINRELAXORFERROELECTRICS—AJUBILEEREVIEWWOLFGANGKLEEMANNAngewandtePhysik,Universita€tDuisburg-EssenD-47048Duisburg,Germanywolfgang.kleem

2、ann@uni-due.deReceived14January2012Revised2April2012Published15June2012SubstitutionalchargedisorderasinPbMg1=3Nb2=3O3,structuralcationvacanciesasinSrxBa1
xNb2O6andisovalentsubstitutionofo®-centeredcationsasinBaTi1
xSnxO3andBaTi1
xZrxO3giverisetoquenchedelectricrandom-¯elds

3、(RFs),whichweproposedtobeattheoriginofthepeculiarbehaviorofrelaxorferroelectrics20yearsago.Theseare,e.g.astrongfre-quencydispersionofthedielectricresponseandanapparentlackofmacroscopicsymmetrybreakinginthelowtemperaturephase.BotharerelatedtomesoscopicRF-drivenphasetransiti

4、ons,whichgiverisetoirregularlyshapedquasi-stablepolarnanoregionsbelowthecharacteristictemperatureT*,butabovetheglobaltransitiontemperatureTc.Theirco-existencewiththeparaelectricparentphasecanbemodeledbytime-dependent¯eldequationsunderthecontrolofquenchedRFsandstress-freest

5、rain(inthecaseoforderparameterdimensionn2).TransitionsintoglobalpolarorderatTcmayoccurinuniaxialrelaxorsasobservedontheuniaxialrelaxorferroelectricSr0:8Ba0:2Nb2O6andcomeclosetoRFIsingmodelcriticality.Re-entrantrelaxortransitionsasby123.138.79.200on10/11/12.Forpersonaluseo

6、nly.observedinsolidsolutionsofBa2Pr0:6Nd0:4(FeNb4)O15areproposedtoevidencethecoexistenceofdistinctnormalandrelaxorferroelectricphaseswithintheframeworkofpercolationtheory.J.Adv.Dielect.2012.02.Downloadedfromwww.worldscientific.comKeywords:Ferroelectrics;relaxors;dielectric

7、response;quenchedrandom¯elds;polarnanoregions.1.RandomFieldInteractionsystems,6respectively,whileacorrespondinginFerroelectricRelaxorsnomenclaturehadbeenmissingintheworldofpolarsystems.ItseemedevidenttousthattheprototypicalRecentlytheenigmaofrelaxorferroelectrics(relax-2,3

8、relaxorPbMg1=3Nb2=3O3(PMN),undoubtedlyorsforshort)wasclaimedtocomeclosetobedeci-meetsthef