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1、journalJ.Am.Ceram.Soc.,84[4]753±58(2001)ContributionofStructuretoTemperatureDependenceofResonantFrequencyinthe(12x)La(Zn1/2Ti1/2)O3zxATiO3(A5Ca,Sr)System²²,³²Seo-YongCho,Hyuk-JoonYoun,Hyo-JongLee,*andKugSunHongSchoolofMaterialsScienceandEngineering,SeoulNationalUniversity,Seoul,151-742,Ko
2、reaandMicro-RadiowaveTechnology,Ltd.,Seoul,150-010,KoreaThecrystalstructureandmicrowavedielectricpropertiesof7termdependsonthestructureofthecompound.Inthecaseofthe(12x)La(Zn1/2Ti1/2)O3zxSrTiO3and(12x)La(Zn1/2Ti1/2)-perovskites,compoundshavingatiltoftheoxygenoctahedraOzxCaTiOsystemwereinve
3、stigated.X-raypowderdiffrac-appeartoexhibitapositivet.10Forexample,thecorrelation33etionshowedthatcationorderingdisappearedatx>0.3forbetweenthetiltofoxygenoctahedraandtewasinvestigatedforbothsystems.However,infraredspectrademonstratedthat(Ba,Sr)(MgTa)Oand(Ba,Sr)(ZnNb)Osystems.2,111/32/331
4、/32/33short-rangecationorderingcouldexistatx50.4.PermittivityThesignandmagnitudeoftechangedrapidlynearthecomposi-andthetemperaturecoefficientoftheresonantfrequency(tf)tionatwhichantiphasetiltingappeared.Sr(Zn1/3Nb2/3)O3,whichofbothsystemsexhibitednonmonotonicvariationswithcom-hasoctahedra
5、ltilting,showspositivete,whileBa(Zn1/3Nb2/3)O3position.Bothsystemsexhibitedatofzeroatthesamewithouttiltingexhibitsanegativet.2Suchcoincidencebetweenfecompositionofx50.5althoughthetfofSrTiO3wasabouttwopositiveteandoctahedraltiltingwasalsofoundinseveraltimeslargerthanthatofCaTiO.Thebehavior
6、ofthepermit-A21B41Otypecomplexperovskitescompounds.12Itissug-33tivityandtfweredescribedbythetiltingofoxygenoctahedragestedthattheexistenceofoctahedraltiltingreducestherestoringandcationordering.TherelationbetweentandcationforceandmakestheCtermlessnegative.10Morerecently,aforderingofLa(Zn1
7、/2Ti1/2)O3wasdiscussedinconjunctionwithshort-rangemodulationofthecrystalstructureratherthanachangetheexperimentalresultsonmetalhalides.Itissuggestedthatinoxygenoctahedraltiltingwassuggestedastheoriginofthetecationorderinginducedanegativetfandsuppressedtheandthepermi
