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1、EffectofstructuralchangesincomplexperovskitesonthetemperaturecoefficientofthereativepermittivityE.L.Colla,I.M.Reaney,andN.SetterLaboratoiredeGramique,EPFL,A&X-DEcublens,1015Lausanne,Switzerland(Received4January1993;acceptedforpublication3May1993)Thedielec
2、tricbehaviorandstructureoftheSr(Zn,,,Nb,,s)O,-Ba(Zn,,,NbV3)03solidsolutionhavebeeninvestigatedwiththeintentionofunderstandingtherelationshipbetweenthestructuralchangesandthetemperaturecoefficientoftherelativepermittivityrE.Acorrelationbetweenthevalueofr,a
3、ndtheoccurrenceofO-octahedratiltshasbeenestablished.Theoccurrenceofferroelasticdomainsandtheirinfluenceonr,hasalsobeeninvestigated.Itisproposedthattheresultsobtainedcanbeusedtogeneralizeaboutthestructure-propertyrelationshipsincompoundsofthesameclass.1.IN
4、TRODUCTIONarisesasaresultofacomplexseriesofoctahedratilttransitions.’BaZr03,however,remainscubic,Pm3m,Complexperovskiteceramicswithhighpermittivitythroughouttheperovskitephaseregion,undergoingnotiltandlowdielectriclossareusedasdielectricresonatorsatordisp
5、lacivetransitions.microwavefrequencies.’Oneofthemostselectivecharac-Glazer6V7gaveadescriptionofoctahedraframeworks,teristicforthistypeofdielectricmaterialisthetempera-tiltedthroughsmallanglesaroundtheprincipalaxes,turecoefficientoftheresonantfrequencyrf,w
6、hichisgivenwhichcanoccurinperovskite-structuredcompounds.inbyhisstudyheassignedaspacegrouptoeachsimpletiltcombinationstartingfromtheuntiltedaristotypecubic7f=--bL+ww,structure(Pm3m).Sincetheoctahedraformarigidframe-where,oListhelinearthermal-expansioncoef
7、ficientandrEworkthroughouttheperovskitelattice,thetiltingofonethetemperaturecoefficientoftherelativepermittivity.Theoctahedronaroundaprincipleaxiscausestiltingofallvaluesofrfareusuallypredictedbyempiricalmethods.Sootheroctahedralyinginthesameplane.Thisapp
8、roxi-far,onlyafewstudieshaveattemptedtoassociate7fwithmatelydoublestheunitcellintwodirections.However,intrinsic,structure-relatedparameters,andselectioncrite-theadjacentlayersofoctahedraalongtherotationaxisriaforcom