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1、NanoStructuredMaterials,Vol.11,No.7,pp.831±835,1999ElsevierScienceLtdPergamonCopyright©1999ActaMetallurgicaInc.PrintedintheUSA.Allrightsreserved.0965-9773/99/$±seefrontmatterPIIS0965-9773(99)00373-6EFFECTOFOXYGENDEFICIENCYONTHERAMANSPECTRAANDHYPERFINEINT
2、ERACTIONSOFNANOMETERSnO2C.H.Shek,G.M.LinandJ.K.L.LaiDepartmentofPhysicsandMaterialsScience,CityUniversityofHongKong,TatCheeAvenue,KowloonTong,HongKong,People'sRepublicofChina(ReceivedJuly1,1999)(AcceptedAugust10,1999)AbstractÐTheRamanandMoÈssbauerspectra
3、ofnano-SnO2specimenswithcrystallitesize3±16nmweremeasuredatroomtemperature.Specimenswereannealedatdifferenttemperaturesinoxygenatmosphereandvacuumrespectively.BoththeRamanandMoÈssbauerspectraofthespecimensconsistofcrystallineandinterface(orsurface)compon
4、ents.TheeffectsofoxygendeficiencyontheRamanspectraarepresentedandcorrelatedwiththechangesoftheSn-Obondproperties,whichwereobtainedfromthecorrespondingMoÈssbauerspectra.©1999ActaMetallurgicaInc.1.IntroductionRamanscatteringhasrecentlybeenusedtostudythesur
5、facemodeandfinite-sizeeffectofnanostruc-turematerials[1±5].Chuuetal.[1]showedthatfornano-scaleCdScrystallites,thesurfacemodesandsizeeffectsaremanifestedbyadditionalbandstothenormalmodesofthesinglecrystal.Whenthegrainsizesbecomeextremelysmallandthevolumef
6、ractionoftheinterface(orsurface)componentiscomparabletothatofthecrystallinecomponent,thesurfacemodesbecomedominant.IntheRamanspectraofthenano-scaleSnO2withaveragegrainsizelessthan6nm,twonewcharacteristicbandscontributedbythesurfacephononmodesappear[2].Un
7、likeTindioxide,thegrainsizeofnano-scaleTiO2hadnoeffectontheobservedRamanspectrainspiteofthefactthatbothTiO2andSnO2possessthesamecrystalsymmetry(tetragonal)[4].Oxygendeficiencies,however,stronglyaffecttheRamanspectrumofnano-TiO2byproducinglargeshiftsandbr
8、oadeningofsomeofthespectralbands[6,7].TheeffectsofoxygendeficienciesontheRamanspectraofnano-SnO2arenotreportedintheliterature.Ontheotherhand,MoÈssbauerspectraofnanometermaterialsconsistoftwosub-spectracorrespondingtothecry
