材料科學(xué)基礎(chǔ)課件

材料科學(xué)基礎(chǔ)

FundamentalofMaterials

LessononeMaterialsSciencedealswiththerelationshipbetweenthemacroscopicpropertiesandthemicroscopicstructures.§1.1AtomicstructureⅠ.Atomicnumbersandatomicmasses1.AtomicModelsChapterIAtomicStructureandBonding2.AtomicnumbersTheatomicnumberofanatomindicatesthenumberofprotons(positivelychargedparticles)whichareinitsnucleus,andinaneutralatomtheatomicnumberisalsoequaltothenumberofelectronsinitschargecloud.Alltheelementshavebeenclassifiedaccordingtoelectronconfigurationintheperiodictable.Theperiodictable

IA

堿金屬堿土金屬過渡元素

01HIIA

主族金屬非金屬稀有氣體

IIIAIVAVAVIAVIIAHe2LiBe

輕稀土金屬重稀土金屬貴金屬

BCNOFNe3NaMgIIBIVBVBVIBVIIBVIIBIBIIBAlSiPSClAr4KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr5RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe6CsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAtRn7FrRaAcRfDbSgBhHsMtUunUuuUub

鑭系LaCePrNdPmSmEuGdTbDyHoErTmYbLu

錒系A(chǔ)cThPaUNpPuAmCmBkCfEsFmMdNoLr

3.AtomicmassTherelativeatomicmassofanelementisthemassingramsof6.023×1023atoms(Avogadro’snumberNA)ofthatelement.Ⅱ.Theelectronicstructureofatoms1.Quantumnumbers

Quantumnumbersarethenumbersinanatomthatassignelectronstodiscreteenergylevels.Theenergyleveltowhicheachelectronbelongsisdeterminedbyfourquantumnumbers.

Theprincipalquantumnumber

n

Thesubsidiaryquantumnumber

l

Themagneticquantumnumber

mlElectronspinquantumnumberms2.Atomicsize3.Electronconfigurations

PauliexclusionprincipleThisprinciplestipulatesthateachelectronstatecanholdnomorethantwoelectrons,whichmusthaveoppositespins.Electronswiththesamesubsidiaryquantumnumberhaveasmanyparallelspinsaspossible.3.Electronegativity

Electronegativeelementsarenonmetallicinnatureandacceptelectronsinchemicalreactionstoproducenegativeions,oranions.Electronegativitydescribesthetendencyofanatomtogainanelectron.Foratomicsystems:Bondingenergies:Ⅱ.Primaryinteratomicbonds

1.Ionicbonding

Ionicbondingisalwaysfoundincompoundsthatarecomposedofbothmetallicandnonmetallicelements,elementsthataresituatedatthehorizontalextremitiesoftheperiodictable.InterionicForces

Z1,Z2＝numberofelectronsremovedoraddedfromtheatomsduringtheionformatione

＝electroncharge

a

＝interionicseparationdistance

ε0＝permittivityoffreespace＝8.85×10-12C2/(N·m2)InterionicEnergiesAttractiveenergyRepulsiveenergyExampleproblem2.1

IftheattractiveforcebetweenapairofMg2+andS2-is1.49×10-8NandiftheS2-ionhasaradiusof0.184nm,calculateavaluefortheionicradiusoftheMg2+ioninnanometers.Solution2.CovalentbondingMaterialswithcovalentbondingarecharacterizedbybondsthatareformedbysharingofvalenceelectronsamongtwoormoreatoms.3.MetallicbondingMetallicbondingoccursinsolidmetals.Inmetalsinsolidstate,atomsarepackedrelativelyclosetogetherinasystematicpatternorcrystalstructure.Ⅲ.Secondarybonding

（VanDerwaalsbonding)Thedrivingforceforsecondarybondingistheattractionoftheelectricdipolescontainedinatomsormolecules.Anelectricdipolemomentiscreatedwhentwoequalandoppositechargesareseparated.NeutralatomEVanDerwaalsbondingAdipolemomentisdefinedasthechargevaluemultipliedbytheseparationdistancebetweenpositiveandnegativecharges,orLondonforcesIftheinteractionsarebetweentwodipolesthatareinducedinatomsormolecules,werefertothemasLondonforces.1.VanderwaalsinteractionsDebyeforcesWhenaninduceddipoleinteractswithamoleculethathasapermanentdipolemoment,werefertothisinteractionasaDebyeinteraction.KeesomforcesIftheinteractionsarebetweenmoleculesthatarepermanentlypolarized,werefertotheseasKeesominteraction.2.SecondarybondingFluctuatingDipolebondsThesebondingforcesarisebecausetheasymmetricaldistributionofelectronchargedistributionintheseatomscreateselectricdipoles.PermanentDipolebondsPermanentDipolebondsexistbetweenadjacentpolarmolecules.3.MixedbondingIonic-CovalentMixedbonding

Metallic-CovalentMixedBondingMetallic-IonicMixedBondingXAandXBaretheelectronegativitiesoftheatomsAandBinthecompound2.Classificationofmaterialsbasedonstructure

Regularityinatomarrangement——periodicornot(amorphous)Crystalline:Thematerialsatomsarearranged inaperiodicfashion.Amorphous:Thematerial’satomsdonothave along-rangeorder(0.1～1nm).Singlecrystal:intheformofonecrystal

grainsPolycrystalline:

grainboundariesⅡ.Spacelattice1.

Definition:Spacelatticeconsistsofanarrayofregularlyarrangedgeometricalpoints,calledlatticepoints.The(periodic)arrangementofthesepointsdescribestheregularityofthearrangementofatomsincrystals.2.

TwobasicfeaturesoflatticepointsPeriodicity:Arrangedinaperiodicpattern.Identity:Thesurroundingsofeachpointinthelatticeareidentical.Alatticemaybeone,two,orthreedimensionaltwodimensionsSpacelatticeisapointarraywhichrepresentstheregularityofatomarrangements

(1)(2)(3)

a

bThreedimensions

EachlatticepointhasidenticalsurroundingenvironmentⅢ.UnitcellandlatticeconstantsUnitcellisthesmallestunitofthelattice.Thewholelatticecanbeobtainedbyinfinitiverepetitionoftheunitcellalongit’sthreeedges.Thespacelatticeischaracterizedbythesizeandshapeoftheunitcell.Howtodistinguishthesizeandshapeofthedeferentunitcell?

Thesixvariables,whicharedescribedbylatticeconstants

——

a,b,c;α,β,γLatticeConstantsa

c

b

αβγa

c

b

αβγ§2.2CrystalSystem&LatticeTypes

Ifarotationaroundanaxispassingthroughthecrystalbyanangleof360o/ncanbringthecrystalintocoincidencewithitself,thecrystalissaidtohavean-foldrotationsymmetry.Andaxisissaidtoben-foldrotationaxis.

Weidentify14typesofunitcells,orBravaislattices,groupedinsevencrystalsystems.Ⅰ.Sevencrystalsystems

Allpossiblestructurereducetoasmallnumberofbasicunitcellgeometries.Thereareonlyseven,uniqueunitcellshapesthatcanbestackedtogethertofillthree-dimensional.Wemustconsiderhowatomscanbestackedtogetherwithinagivenunitcell.SevenCrystalSystemsTriclinica≠b≠c

，α≠β≠γ≠90°Monoclinica≠b≠c

，α＝β＝90°≠γ

α＝γ＝90°≠βOrthorhombica≠b≠c

，α＝β＝γ＝90°Tetragonala＝b≠c

，α＝β＝γ＝90°Cubica＝b＝c

，α＝β＝γ＝90°Hexagonala＝b≠c

，α＝β＝90°γ＝120°Rhombohedrala＝b＝c

，α＝β＝γ≠90°Ⅱ.14typesofBravaislattices1.DerivationofBravaislatticesBravaislatticescanbederivedbyaddingpointstothecenterofthebodyand/orexternalfacesanddeletingthoselatticeswhichareidentical.7×4＝28Deletethe14typeswhichareidentical28－14＝14+++PICF2.14typesofBravaislatticeTricl:simple(P)Monocl:simple(P).base-centered(C)Orthor:simple(P).body-centered(I).base-centered(C).face-centered(F)Tetr:simple(P).body-centered(I)Cubic:simple(P).body-centered(I).face-centered(F)Rhomb:simple(P).Hexagonal:simple(P).Crystalsystems(7)Latticetypes(14)PCFI

ABC1Triclinic√2Monoclinic√√or√(γ≠90°orβ≠

90°

)3Orthorhombic√√or√or√√√4Tetragonal√√5Cubic√√√6Hexagonal√7Rhombohedral√SevencrystalsystemsandfourteenlatticetypesⅢ.PrimitiveCellForprimitivecell,thevolumeisminimumPrimitivecellOnlyincludesonelatticepointⅣ.ComplexLatticeTheexampleofcomplexlattice120o120o120oExamplesandDiscussions1.Whyarethereonly14spacelattices?

ExplainwhythereisnobasecenteredandfacecenteredtetragonalBravaislattice.P→CI→FButthevolumeisnotminimum.2.CriterionforchoiceofunitcellSymmetryAsmanyrightangleaspossibleThesizeofunitcellshouldbeassmallaspossibleExercise1.Determinethenumberoflatticepointspercellinthecubiccrystalsystems.Ifthereisonlyoneatomlocatedateachlatticepoint,calculatethenumberofatomsperunitcell.2.DeterminetherelationshipbetweentheatomicradiusandthelatticeparameterinSC,BCC,andFCCstructureswhenoneatomislocatedateachlatticepoint.3.DeterminethedensityofBCCiron,whichhasalatticeparameterof0.2866nm.+=Fe:Al=1:1FeAlThedifferencebetweenspacelatticeandcrystalstructure2×3atoms/cell1.BCC

Example:α-Fe,V,Nb,Ta,Cr,Mo,W,alkalimetals

n=

2atoms/cell

CN=8

Thenumberofnearestneighboursaroundeachatomiscalled——CoordinationNumber.Ⅱ.Typicalcrystalstructuresofmetals

Packingfraction

＝

Todetermineξ,Theatomislookedasahardsphere,andthenearestneighbourstoucheachother.∴ForBCC,

Volumeofatoms/cellVolumeofunitcell2.FCC

Example:

γ-Fe,Al,Ni,Pb,Cu,Ag,Au,stainlesssteal

n=8×1/8+6×1/2=4atoms/cell

CN=12

3.HCP?????????????????

Example:

Be,Mg,Zn,Cd,Zr,HfTi(lowtemperature)

n＝

CN＝12

ξ＝0.74Structurea0

vs.rAtomspercellCoordinationNumberPackingfactorExamplesSC160.52Polonium(Po),α-MnBCC280.68Fe,Ti,W,Mo,Nb,Ta,K,Na,V,Zr,CrFCC4120.74Fe,Cu,Au,Pt,Ag,Pb,NiHCP2120.74Ti,Mg,Zn,Be,Co,Zr,Cd4.Summary§2.4IntersticesintypicalcrystalsofmetalsⅠ.TwotypesofInterstitialsintypicalcrystals

Octahedralinterstitial

TetrahedralinterstitialDefinition:

Inanyofthecrystalstructures,therearesmallholesbetweentheusualatomsintowhichsmalleratomsmaybeplaced.Theselocationsarecalledinterstitialsites.1.OctahedralinterstitialBCCFCCHCP2.TetrahedralinterstitialBCCFCCHCPⅡ.Determinationofthesizesof

interstitialsDefinition:

Bysizeofaninterstitialwemeandiameterofthemaximumhardspherewhichcanbeaccommodatedintheinterstitialwithoutdistortingthelattice.didadiameterofinterstitialatomdiameterofatominlatticepoint＝Octahedralinterstitialconditionfortouching

ForBCCForFCCTetrahedralinterstitialHLADCBinterstitialhostatomForBCCForFCCSummarynCNξintersticesdi/daoct.tete.oct.tete.BCC280.6866/2=31212/2=60.150.29FCC4120.7444/4=188/4=20.410.22HCP6120.7466/6=11212/6=20.410.22ExamplesandDiscussionsBothFCCandBCCareclose-packedstructureswhileBCCismoreopen?Theinterstitialatomsmostlikelyoccupytheoct.interstitialpositioninFCCandHCP,whileinBCCtwotypesofinterstitialcanbeoccupiedequally.3.ThesolidsolubilityinBCCismuchlowerthaninFCC.4.DiffusionofinterstitialatomsinBCCdiffusionismuchfasterthaninFCCorHCPatsametemperature.5.DeterminetherelationshipbetweentheatomicradiusandthelatticeparameterinSC,BCC,andFCCstructureswhenoneatomislocatedateachlatticepoint.6.DeterminethedensityofBCCiron,whichhasalatticeparameterof0.2866nm.Solution:ForaBCCcell,Atoms/cell=2

a0=0.2866nm=2.866×10－8cmAtomicmass=55.847g/molVolumeofunitcell=a03=23.54×10－24cm3/cellDensity1.Stepstodeterminatetheplaneindices:

Establishasetofcoordinateaxes

Findtheinterceptsoftheplanestobeindexedona,b

and

caxes(x,y,z).a

c

b

x

y

z

Ⅱ.PlaneindicesTakethereciprocalsoftheintercepts1/x,1/y,1/z.Clearfractionsbutdonotreducetolowestintegers.Enclosetheminparentheses,(hkl)

Example:1/2,1,2/32,1,3/2(423)

Planeindicesreferredtothreeaxesa,b

and

c

arealsocalledMillerIndices.SeveralimportantaspectsoftheMillerindicesforplanesshouldbenoted:

Planesandtheirnegativesareidentical.Therefore.

Planesandtheirmultiplesarenotidentical.

Incubicsystems,adirectionthathasthesameindicesasaplaneisperpendiculartothatplane.2.Theimportantplanesincubiccrystals(110)(112)(111)(001)3.Afamilyofplanesconsistsofequivalentplanessofarastheatomarrangementisconcerned.Total:6Total:4Total:12Total:4×3！=24Ⅲ.DirectionIndices1.DerivationforthecrystallographicdirectionAsthefirstabove,settheoriginonthedirectiontobeindexed.Findthecoordinatesofanotherpointonthedirectioninquestions.Reducetothreesmallestintegers:u,v,w.Encloseinsquarebrackets[uvw].2.Theimportantdirectionincubiccrystals:<100>:crystalaxes<110>:facediagonal<111>:bodydiagonal<112>:apicestooppositeface-centers3.Familyofdirectionsconsistsofcrystallographicallyequivalentdirections,denoted<uvw>e.g.

§2.6HexagonalaxesforhexagonalcrystalsⅠ.Whychoosefour-axissystem?

Fourindiceshasbeendevisedforhexagonalunitcellsbecauseoftheuniquesymmetryofthesystem.acbⅡ.Planeindices(hkil)Itcanbeproved:i≡－(h＋k)Importantplanes:a1a2a3cⅢ.Directionindices[uvtw]

Tomaketheindicesunique,anadditionalconditionisimposed.----Let

t＝－(u＋v)ImportantdirectionsTransformationofindicesTransformationof3to4indices,orviceversa.Supposewehaveavector,whose3indices[uvw],and4indices[uvtw].WehaveSinceor:Forexample:1.Quickwayforindexingthedirectionsincubiccrystals:Thevalueofadirectiondependsonitsfeaturewhilethesignondirection.ExamplesandDiscussions2.Thecoordinateorigincanbesetarbitrarily(forexampleonapices,body-center,face-centersetc.),butneveronplaneinquestions,otherwisetheinterceptswouldbe0,0,0.3.Thecoordinatesystemcanbetransferredarbitrarily,butrotationisforbidden.c′

a

c

b

a′

b′

4.Theatomicarrangementandplanardensityoftheimportantdirectionincubiccrystal.planeindicesBCCFCCatomicarrangementplanardensityatomicarrangementplanardensity{100}{110}{111}5.Theatomicarrangementandlineardensityoftheimportantdirectionincubiccrystal.linearindicesBCCFCCatomicarrangementlineardensityatomicarrangementlineardensity<100><110><111>ExerciseCalculatetheplanardensityandplanarpackingfractionforthe(010)and(020)planescubicpolonium,whichhasalatticeparameterof0.334nm.Solution4.Thezone[uvw]containstwoplanes(h1k1l1)and(h2

k2

l2),then5.Theplane(hkl)belongstotwozones[u1

v1

w1]and[u2

v2

w2]if6.Thedistancebetweenadjacentplane(interplanardistance)

d(hkl)＝f(a,b,cα,β,γh,k,l)Fororthorhombic:

Forcubic:Forhexagonalcrystals:7.Thelengthof[uvw]Forcubic:8.TheangleФbetween(h1

k1

l1)and(h2

k2l2)Fororthorhombic:Forcubic:Forhexagonal:9.Theangle

between[u1

v1

w1]and[u2

v2

w2]Fororthorhombic:Forcubic:Forhexagonal:10.Thevolumeofunitcells

V§2.8StackingModeofCrystalsⅠ.Acrystalcanbeconsideredas theresultofstackingtheatomic layers,say(hkl),oneover anotherinaspecificsequence.Forsimplecubic(001)aaaa……(110)abab……ThissequenceiscalledthestackingorderⅡ.Comparisonofstackingmodeof HCPandFCCHCPstackingorder:ABABABAB……1.HCP2.FCCStackingorderof(111)：ABCABCABC……AAABBBCCCⅢ.StackingfaultForHCP:

normalorder:ABABAB……faultorder:ABCABAB……ForFCC：

normalorder:ABCABCABC……faultorder:ABCACABCA……ABCACBCABC……ABCABABAB……ABCACBA……Ⅳ.TransformationofhexagonaltorhombohedralindicesandviceversacHaHbHcRaRbRsinglecrystalpolycrystalgraingrainboundaryⅡ.AllotropySamecrystalhasdifferentcrystallographicstructureatdifferentcondition.

Examples:C,graphite,diamond,CNTBCCBCCFCCGraphiteC60moleculeCarbonNanotubes§3.1BasicconceptsofalloysⅠ.DefinitionAnalloyisthecombinationofmetal(s)withotherelementsthroughchemicalbonding.

Ⅱ.Terminology

1.

Component(orconstituent)onecomponentsystemtwocomponentsystembinarysystemthreecomponentsystemternarysystemfourcomponentsystemquarternarysystemfivecomponentsystemquinarysystemmulti-componentsystem2.

CompositionItcanbeexpressedeitherbyatomicpercentage(molfraction)XaorbymasspercentageXm3.PhaseAphaseisahomogeneouspartofthematerialinwhichnoabruptchangeincomposition,structureandpropertiesoccurs.Analloymaybesinglephaseormulti-phasematerial.4.StructureStructureisageneraltermforthecombinationofatomarrangementincludingthetypesamountsanddistributionofalltypesofmaterialaswellasgrainsize,defectetc.Ⅲ.ClassificationofAlloyPhases1.AccordingtostructureSolidSolutionCompoundInSolidSolution,atomsofdifferentcomponentshareacommonlatticeinvariableproportion.2.AccordingtopositionofthealloyinphasediagramTerminalS.S.

IntermediateS.S.orsecondaryS.S.

αBAβα+β§3.2FactorsAffectingtheStructureofAlloyPhase1.WhatissizefactormetallicradiirA+rB=dionicradiir++r-=dcovalentradiisinglebondradiusVanderWaalsradiiAtomicradii

CNradiiBCCFCC

CNofBCC:8()+6(a)CNofFCC:12()rα==rβ===0.12557nm=0.128674nmGoldschmidtatomicradiiistheradiiofatominstructureswithCN=12Sizefactorisdefinedas

2.WhatisElectrochemicalfactor——ElectronegativityXXrepresentstheabilityofanatomofanelementinthecompondtoattractelectronstoitself.Pauli’sempiricalrule:n:valence

r(1):simplebondradiusEAA——bondingenergybetweenA-A

atomsEBB——bondingenergybetweenB-BatomsEAB——bondingenergybetweenA-B

atoms3.Electronconcentration(e/a)Electronconcentration(e/a)isthenumberofvalenceelectronsperatomontheaverage.i.g.forCuZn:e/a=3/2=1.5§3.3SolidSolutionⅠ.Classification1.AccordingthepositionofsoluteatomsinthelatticeofthesolventSubstitutionalS.S.InterstitialS.S.2.AccordingtheregularityofthepositionoccupiedbysoluteatomsOrderedS.S.DisorderedS.S.1＋3＋12×1/4＋4＋1＝12∴Fe12Al4＝Fe3Al3.Accordingtosolidsolubility0~100%continuousseriesofS.SS.SwithrestrictedsolubilitysummarysubstitutionalS.Sprimary(terminal)interstitialS.Ssecondary(intermediate)orderedS.ScontinuousS.SdisorderedS.SS.SwithrestrictedsolubilityEx.Writeoutinfullthecoordinatesofallcationsandanionsinnucleus,WurtziteandCaF2referredtoabc

axesoftheanionssublattice.Ⅱ.DeterminationoftypesofS.S∴

istheaverageatomicweighweightedbycomposition

Comparenwithno(atomsperunitcellofsolvent)

n=no:idealsubstitutionalS.S.

n>no:interstitialS.S.

n<no:vacantS.S.Ⅲ.Hume-RotheryRuleforprimarysolidsolubility1.Sizefactor:Sizefactor＝×100％d0-dtd0

Ifsizefactor＞15％solubilityisverysmall.NiOcanbeaddedtoMgOtoproduceasolidsolution.Whatotherceramicsystemsarelikelytoexhibit100%solidsolubilitywithMgO?r(?)crystalstructureCd+2inCdO0.9747NaClCa+2inCaO0.9950NaClCo+2inCoO0.729NaClFe+2inFeO0.7412NaClSr+2inSrO1.1270NaClZn+2inZnO0.7412NaClFeO-MgOsystemwillprobablydisplayunlimitedsolidsolubility.CoOandZnOsystemsalsohaveappropriateradiusratiosandcrystalstructures.Exampled01.15d00.85d0dZZ1Z2

2.CrystalstructureThematerialsmusthavethesamecrystalstructure;otherwisethereissomepointatwhichatransitionoccursfromonephasetoasecondphasewithadifferentstructure.

3.Electrochemicalfactor

IfthedifferenceinXisgreat,thesolubilityisalsoveryrestricted.Formationofstablecompoundwillrestrictthesolidsolubility.Parameter:Electronegativity(x)

SemiemperiesformulasWhere:r1——singlebondradius

n——valencyx0x0+0.4x0－0.4xRR00.85R01.15R0Dorken-Gurrygraphic

4.Electronconcentrationfactor,e/a

e:thenumberofvalenceelectrons

a:thenumberofatoms

e/a

=averagenumberofvalenceelectronsperatom.

Experimentalfindings:Zn,Ga,Ge,AsinCu(solute-solvent)

Ifcompositionisexpressedintermsofe/aratherthanat%,thesolidsolubilityofallelementsinCuwillberoughlythesame.

Structurevs.e/a

forCuZnalloysystem

α(CuZn)——e/a=3/2=21/14

β(Cu5Zn8)——e/a=21/13

γ(CuZn3)

——e/a=7/4=21/12

Ⅳ.PropertiesofS.S1.latticeconstantsproperties

Vagard’slaw

ass=ao+(a-ao)xforalloyS.S

Δa=K(ZA-ZB)2

ZA,ZBarevalencesofsoluteandsolvent.

aCuAuNix1.00正偏差負偏差

ro＞r+＋r－

ro＝r+＋r－

stableioniccompound

ro＜r+＋r－

thereissomecovalentboundingstableunstableanionpolyhedronCN＋()minhexahedron80.732octahedron60.414tetrahedron40.225trigonal30.1552.ValenceruleThereisadefiniterelationbetweenvalenceandCN.LetSbethestrengthofelectrostaticbondingbetweenapairofanionandcation

ifS1＝S2＝……＝S,Then

Z

＝(CN－)×S＝（CN－）×（Z+/CN+）3.Theanionpolyhedronprefertoshareapexinsteadofsharingedgesorfaces:§3.5CrystalStructureofCeramicMaterials

ABAB2A2B3ABO3AB2O4Ⅰ.ABtype

1.NaCl

r+/r－＝0.54∴octahedron＝>

CN+＝6

Z－＝1＝CN－(Z+/CN+)＝CN－×1/6∴CN－＝6

2.CsCl

r+/r－＝0.91

∴hexahedron＝>CN+＝8

Z－＝1＝CN－(Z+/CN+)＝CN－×1/8∴CN－＝83.Zincblende(ZnS)CN－＝4 CN+

＝44.Wurtzite(ZnS,ZnO)S(O)＝1/2＋1/2＋1

＝2Zn＝1/4×4＋1

＝2Ⅱ.AB2type1.Fluorspar(CaF2)Li2ONa2OCN+

＝8CN-

＝42.Rutile(TiO2)Ⅲ.A2B3type()Ⅳ.ABO3type(BaTiO3,CaTiO3)Ⅱ.Formation

A→←BThepropertyofAmBnisbetweenthatofAandB.Ⅲ.Factorgoverningthestructureof“compounds”.1)Electrochemicalfactor(X)2)Electronconcentration(e/a)3)SizefactorMetalNonmetalMetalloid§3.7NormalValenceCompoundsⅠ.Definition:

Ifthenumberofvalenceelectronsofthecationissufficienttocompleteoctahedronoftheanion,thecompoundiscalledthenormalvalencecompounds.Example:CmAn

meC＝n(8－eA)sometimes:m(eC－eCC)＝n(8－eA－eAA)Ⅱ.Classification

accordingtostructure1.NaClandCaF2types

NaCl:(MgCaSrBa)(SeTe)(MnPbSn)(SeTe)CaF2:PtSn2PtIn2Pt2PAnti-CaF2:Mg2(SiGeSnPb)Cu2SeLi3AlN2LiMg(NAsSbBi)AgMgAs

2.Diamond,Zincblende,WurtzitetypesZincblende:(BeZnCaHg)(SSeTe)(AlGaIn)(PAsSb)Wurtzite:(ZnCdMn)S(CdMn)Se3.NiAsstructureExample:

(CrFeCoNi)(SSeSb)(FeCo)Te(MnFeNiPtCn)SnNi(AsSbBi)StructureNormalstate——Ni:As=1:1WhenNidoesnotfullfilloctahedralinterspaces

Ni:As<1:1Extremestate：Nioccupytrigonalinterspaces

Ni:As>1:14.ElectronPhase(Electroncompounds)ForAlloysofIBortransitionmetals,andBgroupmetalsphaseswithsaneorsimilarstructureoccuratapproximatelysomeelectronconcentration(e/a)thesealloysarethereforecalledaselectroncompounds§3.8ElectronPhases

(Hume-Rotheryphases)Feature:⑴Identicalonsimilarstructureoccuratapproximatelythesameelectronconcentration,e/a.Forexample:

CuZn:βCu5Zn8:γCuZn3:ε(HCP)

β:(2+1)/2=21/14