High%Temperature%Thermoelectric%Oxides%Engineered% at%mul8ple%length%scales%for%energy%harves8ng ProgramManager:PatriciaRawls FumioS.Ohuchi(PI)andRajendraK.Bordia(CoAPI) DepartmentofMaterialsScienceandEngineering UniversityofWashington Box352120 SeaPle,WA98195 GrantNo.DEAFE0007272 (June1,2012AMay31,2013) GraduateStudents:ChristopherDandeneauandYiHsunYang June%10,%2013% The%UCR%Contractors%Review%Conference% Introduc8on/Mo8va8on%for%Research% WasteHeat TEgenerator n-type " p-type " - + Electrical%power% Thermoelectric(TE)oxidesforwasteheatrecovery GoodhighAtemperaturestability Stableinhos^leenvironments Lowcost/toxicity Oxideswithcomplexstructure: Lowthermalconduc^vity,κ" TailorstoichiometrytomaximizeS 2 σwithlowκ" Significantprogressinthedevelopmentofthe """""patypeteoxides(e.g.,naco 2 O 4 ) SimilarbreakthroughsnotyetachievedfornAtype TEoxides Search%for%highJperformance%nJtype%oxides%
Overall%Goal%of%This%Project%(DEJFE0007272): Developthermoelectric(TE)oxidesforwasteheatrecoveryincoal firedpowerandindustrialplants(highatemp/corrosiveenvironments) Specific%Objec8ves:% Inves^gatepoten^almaterialsandprocessingtechnologyof natypeoxideswithhighteperformanceusinghierarchical designedmicrostructures. Developprocessingroutestomakedesiredcrystallinephases andanisotropicporousstructurestoevaluatetheeffectof microaandmacroaporesonthermoelectricproper^es. Technical%Objec8ve:%%%%% Establishbeneficialcombina^onofferroAelectricity(FE)andthermoA electricity(te)toimprovetheteperformanceofmaterials. Summary%of%Progress%from%FYJ1%(Oct%1,%2011JMay%31,%2012) CombinatorialMaterialsExplora^on(CME), toselectcomposi^onsofsr x Ba 1Ax Nb 2 O 6 (SBN). Solu^onCombus^onSynthesis(SCS)toproduce nanoapowderswithahighdegreeofcrystallinity andphasepurity. Preliminarytestsofthermoelectricperformance frompressurealesssinteredpellets(sbn50). Significantfindings: (σ) dσ dt > 0 σ & S dσ dt < 0 1150C 1100C 1050C 1000C 900C @1250 Cfor4h Publica^on:Journal"of"the"American"Ceramic"Society""""""""""""" "ThermoelectricProper^esofReducedPolycrystallineSr 0.5 Ba 0.5 Nb 2 O 6 FabricatedViaSolu^onCombus^onSynthesis: C.S.Dandeneau,T.W.Bodick,R.K.BordiaandF.S.Ohuchi,JournaloftheAmericanCeramicSociety96(2013)2230. (S) d S dt > 0 Solu^on 900C 1000C 1050C 1100C 1150C BN rich SBN NanoApowders SN rich
Summary%of%Progress%During%This%Period%%% (June%1,%12JMay%31,%13) Scien^ficAchievement TechnologicalDevelopment Reduc^onofSBNxandTEeffect. Sr x Ba 1 x Nb 2 O 6 Sr x Ba 1 x Nb 5+ 2 y Nb n+ y O 6 δ + δ 2 O 2 SitespecificoccupancyinSBNx. Electronicandphononeffectsof ofsbnxonthermalconduc^vity. BePerunderstandingofchange insignofdσ/dtand σ & S XPStoascertainop^mumcond. ofreduc^onforhighteeffect. FurtherrefinementofSCS,and produc^onoflargequan^^es ofnanoapowders. Explora^onofotherniobate composi^onswithhighertc. M:(Sr,Ba) 2 Nb 2 O 7 (M:SBN) Sr x Bi 2Ax Nb 2 O 9 (SBiN) Controlledmicrostructures,grain texture,densifica^onandpores tocontrolteproper^es. C% Sr x Ba 1Jx Nb 2 O 6% (SBNx) % Ferroelectricrelaxor B1% B2% Tungstentetragonalbronze Ionoccupancy (A1) 2 (A2) 4 (C) 4 (B1) 2 (B2) 8 O 30 A1=Sr +2 A2=Sr +2 andba +2 B1andB2=Nb +5 Ba Sr A1% (tetragonal) A2% (pentagonal) a 0.2 SiteOccupancyFactor Podlozhenovet"al., Acta"Crystall."" B"62,960(2006) Sr3d 3/2J5/2%% A2% A1% Ba3d 5/2%% SC SBN61 % SBN61% A2% b c A2%%%%%%%%%%%%%%%%%%%%%%%%%A1% SBN50% SBN30% 3/2 5/2% SBN20% 790 785 784 782 780 778
TE%Results%from%Sr x Ba 1Jx Nb 2 O 6% ElectricalConduc^vity(σ) E SBN50 SBN30 SBN61 Samplesreducedfor3hrs atp(o 2 )~10 A25 atm S (µv/k)% -350-300 -250-200 -150-100 -50 0 SeebeckCoefficient(S) SBN61 SBN50 SBN30 300 400 500 600 700 800 900 1000 T(K)% ThermalConduc^vity(κ) SBN61 SBN50 SBN30 PowerFactor(σS 2 ) E E SBN50 SBN61 SBN30 CaMnO 3 PF~1 µw/cmak 2 FigureofMerit(σS 2 T/κ) SBN61 SBN50 SBN30 BestnAtypematerialknown% CaMnO 3% % 0.15 0.12 0.09 0.06 0.03 0.00 Solidstate reac^on SBN50%as%a%model%compound%to%inves8gate:% 1. Reduc^onofSBNxandTEeffect. 2. SitespecificoccupancyofSr +2 ions,andreduc^on ofnb +5 ionsinsbnx. 3. Electronicandphononcontribu^oninthermal conduc^vityofsbnx. 4. Mechanis^cunderstandingofchangeinsignof dσ/dtandparalleltrendofσands. 5. XPSasatooltoascertainop^mumreduc^on condi^onsforhighteeffect. 6. MicrostructuralaspectsonTEproperty.
Nb%3d 5/2 % 5+ 4+ 3+ 2+ 1+ PowerFactor=σ S 2 red.cond.nb +x Unreduced5.00 900 C4.91 1000 C4.79 1050 C4.76 1100 C4.65 1150 C4.38 1000 C% 1050 C% 1100 C% 900 C% A`er%substrac8ng%Nb 5+ % SBN50:%Nb%3d%XPS$ Nb +(4Aδ) Nb +(2Aδ) Reduc^onofSBN50atvarioustemperatures underh 2 /Arflowingcondi^on. P(O 2 )~10 A25 atm Nb +1 +2 +3 +4 +5 Nb +(4Aδ) tonb +(2Aδ) ra^obecomes maximumarer1000 Creduc^on PFbecomesmaximumbefore Nb +(2Aδ) switcheson. XPSasaprotocoltoascertain idealreduc^oncondi^ons Tes8ng%Protocol%:%%SBN50% Reduc8on%@1000% C%%for%different%8mes% Ba Sr Nb3d 5/2% Nb 3d 5/2 1000 C Anneal Corresponding%TE%proper8es% Seebeck% Nb +(4Aδ) Nb +(2Aδ) 25 hr A2%%%%%%%%%%%%%%%%A1% 1 hr 10 hr 3 hr Elec.%Cond.% % % Pentagonal Tetragonal Reduc8on%causes: A1:Unchanged A2:Broadening/shir Removalofoxygen froma2site? -2 Sr3d % 0 2 Binding Energy A2% A1% (ev, relative to Nb 5+ ) 25hr 10hr 3hr 1hr 0hr 4 Power%Factor% 25%h% % 10h% 1h% % 0.5h%
N1s July9,2013 25h 10h 6 SBN50:%N 2 /5%H 2 %reduc8on%for%25%hrs% N1speak A`er%N2/5%H2% reduc8on% 3h 1150 C 1100 C 1050 C c/s 5 Exteriorofsample 4 3 2 1 0 Closesttocenter UnJreduced% SBN50 SBN30 SBN20-1 440 420 400 380 360 Binding Energy (ev) Movingtowards theexterior 340 450 400 350 Binding Energy (ev) 300 SBN50%(Exterior):%%0,%3,%10,%25%hrs%reduc8on%in%N2/5%H2%at%1000C% 25hrsreduc^on 10hrsreduc^on 3hrsreduc^on Noreduc^on (J%Mat%Sci%(2010)%45:5528J5533% XRDpaPernsrecordedfromNbNfilmsspuPerdepositedat300WanddiffT. XRDpaPernsrecordedfromNbNfilmsspuPerdepositedatat553K,300W, anddifferentnitrogenfluxes. NbN
XRD:SBN50AN2/H2Reduc^on Blue:%AsJreduced%(25%h)%%N2/5%H2% Black:%A`er%lightly%grinding%the%surface% Arergrindingverylightlywithsandpaper: Magnitudeoffirstpeak(ler)issignificantlyreduced Middlepeakdisappears Thirdpeak(right),theintensityofwhichisthesumofNbNand SBN,decreasesinmagnitude ThisregionAnextpage A`er%grinding%lightly%with%sandpaper:% NbN%peaks%disappear% NbO2%peaks%visible%(circles)% Which%Oxygen(s)%is(are)%removed?%% A2% OAvacancy $ Sr +2Aδ$ Nb +4Aδ$ Sr 0.5 Ba 0.5 Nb +5 2 αnb α +n O 6 δ + δ 2 O 2(g) Planned%Experiment%(FYJ3)% Neutrondiffrac^on(atDOEAOakRidgeNeutronDiffrac^onFacility)
Energy%for%Oxygen%Vacancy%Forma8on% Reduc8on%and%Electrical%Conduc8vity%of%SBN $ Reac^ontoformoxygenvacancy Electricalconduc^vity 1 OO V O + 2e + O2( g) 2 1 2 & ΔG # 2 K = [ V ] n ( po ) = exp $ O 2 % kt " & 1 #& ΔG # ln σ = $ + ln B T $ 3k % "% " ΔG 0 ~3.6A3.9eV OAvacancy $ σ = enµ e Sr +2Aδ$ Nb +4Aδ$ Planned%Experiment%(FYJ3)% % EXAFSandhardXAraydiffrac^onanalysis atdoeaapsfacility. Electrical%Conduc8vity% Test%of%Polaron%Hopping%Models% # σ exp T 1 & 1+1 % ( $ ' dσ dt > 0 dσ dt < 0 e - # σ exp T 1 & d+1 % ( $ ' 1150 C 1100 C 1050 C 1000 C 900 C # σ exp T 1 & 3+1 % ( $ ' Fitto1ADor3ADhoppingmodelequallywell: Not%conclusive%% Planned%Experiment%(FYJ3)% e - 1150 C 1100 C 1050 C 1000 C 900 C
SBN50:%Thermal%Conduc8vity" κ = C pαρ Electronic: κ = LσT Phonon: e κ = κ κ l e UnreducedSBN50lowRTκof~1W/mtK Arerreduc^onat1000 C 40%averageincreaseinκ Density(ρ)increasedfrom74%to~79% Largeincreaseinthermaldiffusivity(α) Lawceconduc^onisdominated. Development%of%an%en8rely%new%reduc8on%scheme:%%% %%%%%% Irreversible%Chemical%Reduc8on %(FYJ3)% SBN50%Powder%Processing% Conven8onal%Sintering%(CS)%%%Spark%Plasma%Sintering%(SPS)%%%%SinterJForging%(SF) % % PressurelessAsintering Varieddensity Possiblegraingrowth (abnormalgraingrowth) abnormalgraingrowth Sintered25 CabovepreviousT Pressure+Electricalcurrentinvacuum Extremelyfastsintering^mes(<10min) HighdensitywithfineAgrains(<250nm) CS+uniaxialpressure. Highdensity. Texturedgrains 1µm 10µm ρ~80%ρ th ρ=93%ρ th Focus%on%SPS%and%SF%(FYJ3)% ρ>90%ρ th
Aug22,2013 SinterAforgedSBN50:Surfaceofspecimens XRD 1MPapressure 10MPapressure Aug22,2013 SinterAforgedSBN50:CrossAsec^onofspecimens 1MPapressure 10MPapressure (440) Looked fromside XRD (741)
XRD%Comparison%of%CS%and%SPS%Processes% SBN50(CS) +reduced10hrs Auniquetoreduc^on AuniquetoSPS SBN50(SPS) +oxidized" SBN50(SPS)" PeakbroadeninginSPS Asmallercrystallitesize " SPSprocessinduces: Aslightreduc^on Atexturing Structureanalysis Ainprogress SBN50(CS) @1250 C" 2025303540 Diffrac^onAngle(2θ) Complete% structure%factor% analysis(fyj3)% Ferroelectric%Relaxor%Materials%for%TE%Applica8ons%% UniqueTEproper^esfoundinSBNx σ & S IsthisduetoFerroelectricRelaxors? T c% CurieTemp. % Localpolardomains % T B% BurnsTemp.(PRB28,2527(1983)) % (σ) dσ dt > 0 T c%% Strategyforwideningregion σ & S Comp.T c T B SBNx 0~200 C200~400 C Sr 2 Nb 2 O 7 ~1300 C? SrBi 2 Nb 2 O 9 ~450 C? Thestron^umniobate(Srn Nb n O 3n+2 )systems AApseudo1ADsystem APerovskitestructure AHighlyanisotropic T B%% ElecCond dσ dt < 0 1150C 1100C 1050C 1000C 900C (S) d S T c%% T B%% T c%% T B%% 900C dt > 0 1000C?% Temp 1050C 1100C 1150C
Progress%so%far%(May%31,%2013):% 1. CompletedSCSofSr 2 Nb 2 O 7 (SN)andbasiccharacteriza^on 2 (C2O4) 5 + 2Sr(NO3) 2 + 10NH4NO3 5CO(NH2) 2 Sr 2Nb2O7 + 15CO2 + 30H2O + 17N2 Nb + SBN50vs.Sr 2 Nb 2 O 7 Sr 2 Nb 2 O 7 2. SNATEcharacteriza^ons^llinprogress 3. BiAdopedSNandSrBi 2 Nb 2 O 9 inprogress 4. DevelopmentofSeebecktester,capable ofmeasuringtepropatt>1000 C. Planned%Experiment%(FYJ3)% Farnece Sample Summary%of%Findings% (June1,2012AMay31,2013) 1. DemonstratedSr x Ba 1Ax Nb 2 O 6Aδ (SBNx)aspoten^alcandidatesfornA typeteoxidematerials. 2. Thoroughlystudiedreduc^onprocessesofSBNxinrela^onto theirteeffects. Sitespecificoccupancyintungstentetragonalbronze Changeinsignofds/dTandparalleltrendofSands Electronicandphononcontribu^onsinelectronicand thermalconduc^vity 3. Microstructuralaspectsusingdifferentsinteringtechniques 4. Explora^onofniobatebasedotherferroelectricrelaxors 5. ProvedXPSasatooltoascertainop^mumreduc^oncondi^ons forhighteeffect.
Future%Plans%for%FYJ2(rest)%and%FYJ3% 1. SBNx:Furtherrefinementofscien^ficissues Neutrondiffrac^onforsitespecificoxygenremoval EXAFSandhardxAraydiffrac^onforlocalbondingandcoordina^on TEtransportmechanismsuniquetorelaxors Crystallographictextureinrela^ontoTEtransportproper^es 2. Developmentofanew Chemical%Reduc8on scheme. 3. SBNx:Engineeringdevelopment Mul^plelengthscaleengineeringtoenhanceTEproper^es NanoAmicrocompositesconcept* DevelopmentofprototypeTEdevices 3.Explora^onof(Sr,Ba) 2 Nb 2 O 7 andsr x Bi 2Ax Nb 2 O 9 (SBiN) EffectoflocalpolarnanoAdomainsb/wT c andt B ofrelaxors 4. Publica^onsinprepara^on(current) 1,2:SBNx:XPSrelated 3.SBNx:TE 4.HighTSeebecktester (APLandJAP) (JACerS) (RSciInst) *NanoJMicro%Composites% N40:40%CoSb 3 nanopar^cles Reduc^oningrainsizeadverselyaffectselectronmobility ResearchintonanoAmicrocompositestoscaPerphonons andpreserveσ" Percola^oneffect:Chargecarriers select lowresis^vity pathwhilephononsscaperedbynanopar^cles Miet"al.,App."Phys."Le:.91,172116(2007)
Thank%you%