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1、JOURNALOFAPPLIEDPHYSICSVOLUME94,NUMBER51SEPTEMBER2003RamanspectroscopyandmicrowavepropertiesofCaTiO3-basedceramicsa)H.Zheng,H.Bagshaw,G.D.C.CsetedeGyo¨rgyfalva,andI.M.ReaneyDepartmentofEngineeringMaterials,UniversityofShef?eld,Shef?eld,S13JDUnitedKingdomR.UbicDepartmentofMaterials
2、,QueenMary,UniversityofLondon,London,E14NSUnitedKingdomJ.YarwoodMaterialsResearchInstitute,Shef?eldHallamUniversity,Shef?eld,S11WBUnitedKingdom~Received21April2003;accepted11June2003!xCaTiO32(12x)Sr(Mg1/3Nb2/3)O3~CTSMN!andyCaTiO32(12y)NdAlO3~CTNA!microwaveceramicshavebeenstudiedby
3、x-raydiffraction~XRD!,transmissionelectronmicroscopy~TEM!,andRamanspectroscopy.TEMandXRDrevealedthatallcompositionsunderwentoctahedraltilttransitionsoncooling,generallyresultinginana2a2c1tiltsystem.TheexceptionwastheNdAlO3endmember,whichhadtheR?3cspacegroup,consistentwithana2a2a2t
4、iltcon?guration.Sr(Mg1/3Nb2/3)O3~SMN!,(x50)alsoexhibited1/21/3$hkl%reˉectionsinx-rayandelectrondiffractionpatternsassociatedwith1:2long-rangeorderingoftheB-sitecations.Forx>0.2,no1:2orderedreˉectionswereobserved.Thelong-rangeB-siteorderinginSMNgaverisetosharpRamanbandsat391and825c
5、m21.The391cm21banddisappearedforx>0.2andthewidthofthe825cm21bandbecamebroaderasxincreased.Itwasconcludedthatforsampleswithx>0.2,onlyshort-rangeorderingremainedwhichdecreasedincorrelationlengthasxincreased.InCTNAsolidsolutions,abroadRamanbandoccurredat;800cm21~absentfory50and1andst
6、rongestfory50.5).Thepositionofthisbandsuggestedthatitsoriginwassimilarinnaturetothe;825cm21bandobservedinCTSMNandthereforerelatedtolocalshort-rangecationordering.ArelationbetweenthepresenceofstronglocalorderandpoorQinzero-temperaturecoef?cientoftheresonantfrequencyCTSMN(x'0.2)ispo
7、stulated.?2003AmericanInstituteofPhysics.@DOI:10.1063/1.1598271#I.INTRODUCTIONtwoB-siteionsandonthedifferenceintheirvalencestates,alargerdifferenceforeachcasefavouringorder.ThedegreeCaTiO3-basedperovskiteceramicsarewidelyusedasandnatureoforderingrevealedinx-raydiffraction~XRD!reso
8、natormaterialsinwirelesscommunica
