功能材料双语电功能材料

功能材料双语电功能材料第1页/共62页classificationofelectricalfunctionalmaterials

basedontheconductivemechanism：electronconductionmaterialandionicconductionmaterial.

electronconductionmaterial:semiconductor,conductorandsuperconductor：10-710-610-510-410-310-210-1100101102103104105106conductivityσS/minsulatorsemiconductorconductorsuperconductor：σ→∞第2页/共62页themovementofanionfromonesitetoanotherthroughdefectsinthecrystallatticeofasolidoraqueoussolution,sotheconductivityissmallerbecausethetravellingspeedofionisslowerthanelectron,

theconductivityisnomorethan102S/m，andusuallysmallerthan100S/mionicconductionmaterial第3页/共62页3.1Conductor（1）metal.theconductivityis107~108S/m;

sliver（6.63×107S/m）、copper（5.85×107S/m）

aluminum（3.45×107S/m）（2）alloy.theconductivityis105~107S/m;brass黄铜（1.60×107S/m）,

nichrome镍铬合金

（9.30×105S/m）（3）inorganicnonmetallic.theconductivityis105~108S/m.

graphite石墨(2.5×106S/m).第4页/共62页crystalstructureofgraphite第5页/共62页applicationsofconductorsmetals：cable,electricalmachine,radiationshielding,battery,switch,sensor,informationtransmission,contactmaterial,

etc，alloys:mainlyusedforresistancematerialand

thermocouplematerial,forexampleplatinum-rhodiumplatinumthermocouple（铂铑铂热电偶）inorganicnonmetallic：corrosionresistantconductorsandconductivefiller（导电填料）.第6页/共62页3.2superconductor第7页/共62页SuperconductivitywasdiscoveredonApril

8,1911byDutchphysicist

HeikeKamerlinghOnnes

,whowasstudyingtheresistanceofsolidmercury(汞)atcryogenictemperatures（冷冻温度）usingtherecentlyproducedliquidhelium（液氦）asarefrigerant.Atthetemperatureof4.2K,heobservedthattheresistanceabruptlydisappeared

.Theprecisedateandcircumstancesofthediscoverywereonlyreconstructedacenturylater,whenOnnes'snotebookwasfound.第8页/共62页DefinitionofsuperconductorsSuperconductivity

isaphenomenonofexactlyzero

electricalresistance

andexpulsionof

magneticfields

occurringincertainmaterialswhen

cooled

belowacharacteristic

criticaltemperature.第9页/共62页Elementarypropertiesofsuperconductorsexactlyzeroresistivity（绝对零电阻）

Experimentalevidencepointstoacurrentlifetimeofatleast100,000years.第10页/共62页

Meissnereffect（迈斯纳效应）

thecompleteejectionof

magneticfieldlines

fromtheinteriorofthesuperconductorasittransitionsintothesuperconductingstateejectionof

magneticfieldlines第11页/共62页TheoccurrenceoftheMeissnereffectindicatesthatsuperconductivitycannotbeunderstoodsimplyastheidealizationofperfectconductivityinclassicalphysics.第12页/共62页Theelectricalresistivityofametallicconductordecreasesgraduallyastemperatureislowered.Inordinaryconductors,suchascopperorsilver,thisdecreaseislimitedbyimpurities（杂质）andotherdefects（缺陷）.Evennearabsolutezero,arealsampleofanormalconductorshowssomeresistance.Inasuperconductor,theresistancedropsabruptlytozerowhenthematerialiscooledbelowitscriticaltemperature.第13页/共62页

criticaltemperature

Tc，criticalmagneticfieldHc，criticalcurrentJc（临界温度、临界磁场、临界电流密度）thecharacteristicsofsuperconductivitydisappearwhenthe

temperature

Tc

ishigherthanthe

criticaltemperature

Tc;orhigherthanthecriticalmagneticfieldHc,criticalcurrentJc,theregionsseparateedbyTc、Hc，Jc.第14页/共62页Josephsoneffect（约瑟夫森效应）

TheJosephsoneffectisthephenomenonofsupercurrent—i.e.acurrentthatflowsindefinitely（无限期的）longwithoutanyvoltageapplied—acrossadeviceknownasaJosephsonjunction(JJ),whichconsistsoftwosuperconductorscoupledbyaweaklink.第15页/共62页Theweaklinkcanconsistofathininsulatingbarrier(knownasasuperconductor–insulator–superconductorjunction,orS-I-S),ashortsectionofnon-superconductingmetal(S-N-S),oraphysicalconstrictionthatweakensthesuperconductivityatthepointofcontact(S-s-S).第16页/共62页developmentofsuperconductor77KBymaterial:chemicalelementsalloys

ceramics

organicsuperconductors第17页/共62页ApplicationsSuperconductingmagnets(超导磁体)aresomeofthemostpowerfulelectromagnets(电磁铁)known.TheyareusedinMagneticResonanceImaging(MRI，磁共振成像)/nuclearmagneticresonance(NMR，核磁共振成像)machines,massspectrometers(质谱仪),andthebeam-steeringmagnets(光束转向磁体)usedinparticleaccelerators(粒子加速器).第18页/共62页粒子加速器内部温度：4万亿摄氏度工作温度是-271.3℃，比外太空还冷第19页/共62页Inthe1950sand1960s,superconductorswereusedtobuildexperimentaldigitalcomputersusingcryotronswitches（低温开关）.Morerecently,superconductorshavebeenusedtomakedigitalcircuitsbasedonrapidsinglefluxquantum（快速单量子通量）technologyandRF（radiofrequency，无线电频率）andmicrowavefilters（微波过滤器）formobilephonebasestations.第20页/共62页SuperconductorsareusedtobuildJosephsonjunctionswhicharethebuildingblocksofSQUIDs(superconductingquantuminterferencedevices),themostsensitivemagnetometers（磁力计）known.SQUIDsareusedinscanningSQUIDmicroscopesandmagnetoencephalography（脑磁图）第21页/共62页high-performancesmartgrid（智能电网）,electricpowertransmission（电力输送）,transformers（变压器）,powerstoragedevices,electricmotors（电动机）(e.g.forvehiclepropulsion（汽车驱动）,asinmaglevtrains（磁悬浮列车）),magneticlevitationdevices（磁悬浮装置）,faultcurrentlimiters,（故障电流限流器）andsuperconductingmagneticrefrigeration（超导磁制冷）.第22页/共62页Theycanalsobeusedformagneticseparation(磁选),whereweaklymagneticparticlesareextractedfromabackgroundoflessornon-magneticparticles,asinthepigmentindustries.第23页/共62页核聚变堆用超导线圈第24页/共62页Superconductingsubmarine（超导潜水艇）第25页/共62页超导磁流体推进船1992年1月27日，由日本船舶和海洋基金会建造的，第一艘采用超导磁流体推进器的轮船——“大和”1号在日本神户下水试航。第26页/共62页maglevtrains（磁悬浮列车）近日，国家“十三五”重点研发计划《现代轨道交通专项》启动时速600公里高速磁悬浮交通和时速200公里中速磁浮交通研发项目第27页/共62页superconductingelectricpowertransmission第28页/共62页未来超导体汽车第29页/共62页寻找现实中的哈利路亚山——室温超导体第30页/共62页第31页/共62页第32页/共62页3.3semiconductor第33页/共62页haselectricalconductivitybetweenthatofaconductorsuchascopperandthatofaninsulatorsuchasglass（σ＝10-7～104）Negativetemperaturecoefficient（负的电阻温度系数）:

thermalconductivity

or

electricalresistivityofasemiconductorlowerswithincreasingtemperature,whichisoppositetothatofametal.semiconductor第34页/共62页usefulproperties:passingcurrentmoreeasilyinonedirectionthantheother;showingvariable

resistance(可变电阻);

sensitivitytolightorheat（对光/热敏感）So,electricalpropertiesofasemiconductormaterialcanbemodified（修饰）bycontrolledadditionofimpurities（杂质）,orbytheapplicationofelectricalfieldsorlight.第35页/共62页basicconcepts:Insolid-statephysics,theelectronicbandstructure(orsimplybandstructure)ofasoliddescribesthoserangesofenergythatanelectronwithinthesolidmayhaveandrangesofenergythatitmaynothave(calledbandgapsorforbiddenbands)带隙或禁带.（1）Electronicbandstructure(bandstructure)电子能带结构Physicsofsemiconductors（半导体物理学）第36页/共62页

bandgap,alsocalledanenergygap（能隙）orbandgap（带隙）,isanenergyrangeinasolidwherenoelectronstatescanexist.

generallyreferstotheenergydifference(inelectronvolts)betweenthetopofthevalencebandandthebottomoftheconductionbandininsulatorsandsemiconductors.(2)

BandGap（带隙）第37页/共62页

(3)ForbiddenBand（禁带）energygapshouldbetheenergydifferencebetweentwodifferentenergyband.forexampleconductingbandandvalenceband.However,energyinbetweenthetwobandisallowed.Forbiddenbanddonotallowanyenergyresidentinit第38页/共62页(4)ValenceBand（价带）Insolids,thevalencebandisthehighestrangeofelectronenergiesinwhichelectronsarenormallypresentatabsolutezerotemperature.Onagraphoftheelectronicbandstructureofamaterial,thevalencebandislocatedbelowtheconductionband,separatedfromitininsulatorsandsemiconductorsbyabandgap.theclosestbandbeneaththebandgap.Inmetals,theconductionbandhasnoenergygapseparatingitfromthevalenceband.第39页/共62页(5)Emptyband（空带）：noelectronisfilled

(7)

FilledBand（满带）

(6)ConductionBand（导带）

Theclosestbandabovethebandgap第40页/共62页Thevalenceelectronsareboundto（限制在）individualatoms,asopposedtoconductionelectrons(foundinconductorsandsemiconductors),whichcanmovefreelywithintheatomiclatticeofthematerial.第41页/共62页Thetotallyfilledorbitals（轨道）withhighestrangeofelectronenergiesformvalence,theemptyorbitalwithnoelectronsiscalledtheconductionband.1ev第42页/共62页TheconductivemechanismofthesemiconductorElectronscanbeexcitedacrosstheenergybandgap(fromfilledbandtoemptygap)ofasemiconductorbyvariousmeans,andleavingholesinthefilledband，

Thisprocessisknownas

electron–holepairgeneration.Themovementofelectronsintheconductionbandandholesinthefilledbandcreatecurrent.第43页/共62页typesofsemiconductormaterialsclassifiedaccordingtothecompositionpureelementscompoundssolidsolution第44页/共62页1.ElementsconductorElementsconductorIntrinsicsemiconductor本征半导体

Extrinsicsemiconductor非本征半导体puresemiconductor,nodefect,theconcentrationofimpurityislessthan10-9

addingcontrolledimpuritiestoasemiconductortomodifytheconductivity第45页/共62页themostcommerciallyimportantoftheseelementsaresilicon

（硅）andgermanium（锗）.Siliconandgermaniumareusedhereeffectivelybecausetheyhave4valenceelectronsintheiroutermostshellwhichgivesthemtheabilitytogainorloseelectronsequallyatthesametime.Apuresemiconductor,however,isnotveryuseful,asitisneitheraverygoodinsulatornoraverygoodconductor.Intrinsicsemiconductor第46页/共62页Extrinsicsemiconductor(非本征半导体/杂质半导体)Addingimpurityatoms（杂质原子）toasemiconductingmaterial,knownas“doping”,（掺杂）greatlyincreasesthenumberofchargecarrierswithinit.第47页/共62页Extrinsicsemiconductorn-typep-type

largerelectronconcentrationthanholeconcentration，electronsarethemajoritycarrierslargerholeconcentrationthanelectronconcentration,holesarethemajoritycarriers第48页/共62页N-typesemiconductor（electrondoners）电子施主

groupVA（N、P、As、Sb、Bi）introducedinto

groupⅣAoftheperiodictable（C、Si、Ge、Sn）,createsanextrafreeelectronp-typesemiconductor（holes,acceptors）电子受主

group

ⅢA（B、Al、Ga、In、Ta）allcontainthreevalenceelectrons,whenusedtodopegroupⅣA（C、Si、Ge、Sn），avacantstate(anelectron"hole")iscreated,whichcanmovearoundthelatticeandfunctionsasachargecarrierExtrinsicsemiconductor（非本征半导体）第49页/共62页energybandofsemiconductorn-typesemiconductor:electronisindonerlevel施主能级,theenergydifferencebetween

donerlevelandbottomofconductionband（Ed）ismuchlessthanEg（aboutthreeordersofmagnitude）,soelectroncanbemoreeasilyexcitedtotheconductionbandthanintrinsicexcitation本征激发第50页/共62页forexample:oneoverabillionofAsdopedSi，Eg

is1.6×10-19J，Ed

is6.4×10-21J.oneoverabillionofSbdopedGe，Eg

is1.15×10-19J，Edis1.6×10-21J.第51页/共62页p-typesemiconductor:holeisinacceptedlevel受主能级,theenergydifferencebetween

acceptedlevelandtopofconductionband（Ea）ismuchlessthanEg,soelectroninvalencebandcanbemoreeasilyexcitedtotheacceptedbandandleaveanholeinvalenceband.第52页/共62页binarycompound二元化合物

GaAs、CdS、SiC、GeS、AsSe3,etcByalloyingmultiplecompounds,somesemiconductormaterialsaretunable,e.g.,inbandgaporlatticeconstant晶格常数.Theresultisternary三元,quaternary四元,orevenquinary五元compositionsternarycompound三元化合物

AgGeTe2、AgAsSe2、CuCdSnTe4,pounds第53页/共62页第54页/共62页galliumarsenide(GaAs)hassixtimeshigherelectronmobilitythansilicon,whichallowsfasteroperation;widerbandgap,whichallowsoperation