THEAQUEOUSPROCESSINGOFBARIUMTITANATE: PASSIVATION,DISPERSION,ANDBINDERFORMULATIONS FORMULTILAYERCAPACITORS By ROBERTE.CHODELKA ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOFDOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 1996 Dedicatedto: mymotherandfather EleanorandEdwardChodelka and mysisterandniece,brothers,anddog TheresaandEricaRogers,DavidChodelkaandTimothyChodelka,andZor inappreciationoftheirendlesssupport,guidance,patience,andbeliefinme. ACKNOWLEDGMENTS Iwouldliketotakethisopportunitytothankall ofthe people who made this researchprojectnotonlypossible,butsuccessful. SincerethanksisextendedtoDr.James H. Adair,mycommitteechairandadvisor,forhisscientificguidanceinacademicaffairs andfatherlyadviceinpersonalmatters. Myrelationshipwithhimhasmademenotonlya betterscientist,butabetterhumanbeing. Iwouldliketothanktheothermembersofmy committee,Drs. RobertT. DeHoff,Brij M. Moudgil,andMichaelD. Sacks, fromthe DepartmentofMaterialsScienceandEngineering,RussellS. DragofromtheDepartment ofChemistry,andStephenA.Costantinofromthesponsorofthecurrentresearch,Cabot PerformanceMaterials(CPM),Boyertown, PA. Withouttheiradviceandthemonetary supportfromCPM,thisresearchwouldnothavebeenasuccess. IwouldliketoacknowledgeDr.StanleyBatesandthestaffattheMajorAnalytical InstrumentationCenter(MAIC)attheUniversityofFloridafortheiranalyticalsupportand technical advice, specifically, the high resolution transmission electron microscopy conductedbyDr.AugustoMorrone. Iamgratefultoallmyfriends,bothpastandpresentcolleaguesinDr. Adair's researchgroupandin the Department ofMaterials Science and Engineering, for their technical advice and support. Special thanks goes out to Dr. Sridhar Venigalla, Dr.MelanieCarasso,andsoontobeDrs. CraigHabegerandJeffKerchnerforproof- readingmydissertation,aswellasPamHowellforhersupportandassistanceduringmy enrollmentinthePh.D. programattheUniversityofFlorida. Inthetimesofneed,Ifelt thatIcouldalwaysrelyonmyfriends. IwillneverforgetthecompetitiveHeartscard games,thedepartmentalI.M.sportsteams,andthesocialfunctionsthatmademyyearsat theUniversityofFloridaquiteenjoyable. iii Inclosing,Iwouldliketothankmymother,father,sister,niece,andtwobrothers for the continuous support, guidance, and patience. Theirbelief in me enabled my perseverance. iv TABLEOFCONTENTS ACKNOWLEDGMENTS iii LISTOFTABLES viii LISTOFFIGURES ix ABSTRACT xvi CHAPTERS 1. INTRODUCTION 1 1.1. Introduction 1 1.2. LiteratureReview 2 1.3. ChemicalPassivationoftheBariumTitanateParticleSurfaceviaOxalic Acid 4 1.4. DispersionofAqueousBariumTitanateSuspensions 5 1.5. BinderFormulations 6 1.6. ConclusionsandFutureWork 7 2. LITERATUREREVIEW 8 2.1. Introduction 8 2.2. ProcessingofMultilayerCapacitors 8 2.3. AqueousEnvironment 15 2.3.1.SolubilityofBariumTitanateandTitaniumDioxideinWater 15 2.3.2.PassivationofThermodynamicallyUnstableMetalsandGlasses 20 2.3.3.FeasibilityofPassivatingBariumTitanate 24 2.4. Dispersion 28 2.4.1.ElectrostaticSurfaceChargeFormationandStabilization 28 2.4.2.PolymericDispersion 36 2.4.3.ElectrophoreticBehaviorofTitaniumDioxideandBariumTitanate 38 2.4.4.ElectrophoreticBehaviorofCalciumOxalateMonohydrate 45 2.5. Binders 47 2.6. VariationsintheBa:TiRatioonSinteringofBariumTitanate 47 2.7. CharacterizationTechniques 50 2.7.1. SolutionChemistry 50 2.7.2. SurfaceChargeAnalysis 51 2.7.2.1. LightScatteringTechniques 53 2.7.2.2. ElectroacousticAnalysis 53 2.7.2.3. Sedimentationanalysis 54 v 2.7.3. ParticleObservation 54 2.7.3.1. ScanningElectronMicroscopy 54 2.7.3.2. TransmissionElectronMicroscopy 56 2.7.4. Viscosity 56 2.8. ChapterSummary 59 3. COXHAELMIICCAALCIPDAASDSDIIVTAITOINOSNOFTHEBaTi03PARTICLESURFACEVIA 62 3.1. Introduction 62 3.2. Approach 68 3.3. MaterialsandMethods 70 3.3.1. General 70 3.3.2. BariumTitanatePowderCharacterization 71 3.3.3. PreparationofAqueousBariumTitanateSuspensions 74 3.3.4. PreparationandCharacterizationoftheVariousBariumTitanate PowdersforHighResolutionTransmissionElectronMicroscopy 75 3.4. ResultsandDiscussion 76 3.4.1. SolutionChemistryAnalysis 76 3.4.2. HighResolutionTransmissionElectronMicroscopyAnalysis 81 3.4.3. ElectrophoreticBehaviorofBariumTitanateSuspensionsat VariousSolidsLoading 88 3.4.4. ElectrophoreticBehaviorofBariumOxalateMonohydrateand BariumTitanateSuspensionsatVariousOxalicAcidConcentrations 92 3.4.5. ElectroacousticAnalysisofHighSolidsLoadingBariumTitanate Suspensions 95 3.5. Conclusions 98 4. DISPERSIONOFAQUEOUSBaTi03SUSPENSIONS 101 4.1. Introduction 101 4.2. Approach 106 4.3. MaterialsandMethods 107 4.3.1. PreparationofLowSolidsLoadingBariumTitanateSuspensions 107 4.3.2. HighSolidsLoadingBariumTitanateSlurries 109 4.3.2.1. PreparationofBariumTitanateSlurries 109 4.3.2.2. CharacterizationoftheBariumTitanateSlurries 112 4.4. ResultsandDiscussion 113 4.4.1. PreliminaryStudiesatLowSolidsLoading 113 4.4.1.1. SolutionChemistry 113 4.4.1.2. SedimentationResults 116 4.4.1.3. ElectrophoreticBehavior 123 4.4.2. HighsolidsloadingBariumTitanateSlurries 125 4.5. Conclusions 135 5. BINDERFORMULATIONSFORTHEOXALATE/POLYETHYLENE IMINE-TREATEDBaTi0 SUSPENSIONSFORMULTILAYER CAPACITORS 3 139 5.1. Introduction 139 vi 5.2. Approach 143 5.3. MaterialsandMethods 145 5.3.1. General 145 5.3.2. PreliminaryStudiesLowSolidsLoading 146 5.3.2.1. ElectrophoreticandSedimentationStudies 146 5.3.2.2. PolymerInteractions 147 5.3.3. HighSolidsLoadingBariumTitanateSlurries 148 55..33..33..12.. PChraerpaacrtaetriioznatoifoBnaoTfit0he3SBlaurririuemsTwiittahnaBtienSdleurrrPireessent 114488 5.4. ResultsandDiscussion 149 5.4.1. PreliminaryStudiesatLowSolidsLoading 149 5.4.1.1. ElectrophoreticandSedimentationStudies 149 5.4.1.2. PolymerInteractions 151 5.4.1.3. TitrationCurves 155 5.4.2. HighsolidsloadingBaTi03Slurries 163 5.5. Conclusions 171 CONCLUSIONSANDSUGGESTIONSFORFUTUREWORK 175 6.1. Conclusions 175 6.2. SuggestionsforFutureWork 178 APPENDIXA 180 LISTOFREFERENCES 186 BIOGRAPHICALSKETCH 195 vii LISTOFTABLES Table page 3.1. SummaryofthechemicalconstituentsandpHrangesusedforanalyzing 17oBaTiOjsuspensionsviaelectroacousticanalysis 75 5.1. cSoummpmosairtyiono,fatnhderhseaomlpolgeicadlespirgonpaetritoine,s(waepipgahretntpevricsecnotsitByaaTnid03B,inbignhdaemr yfioerlmdulaptoiinotn)s for the oxalate/polyethylene imine-treated BaTi03 slurry 165 A.l. Summary of the chemical constituents and physical characteristics for BaTiOjslurriespreparedwith0.5w/ooxalicacid,andvaryingamountsof polyethyleneimine(PEI)withoutbinderpresent 181 A.2. Summary of the chemical constituents and physical characteristics for BpoalTyie0th3yslleunrreiiemsinpere(pPaErIe)dwwiitthhou1t.b0iwn/odeorxaplriecseanctid,andvaryingamountsof 182 A.3. Summary of the chemical constituents and physical characteristics for BpoalTyie0th3yslleunrreiiemsinpere(pPaErIe)dwwiitthhou2t.b0i7nodeorxaplriecseanctid,andvaryingamountsof 183 A.4. Summary of the chemical constituents and physical characteristics for BpoalTyie0th3yslleunrreiiemsinpere(pPaErIe)dwwiitthhou3t.0biwn/odeorxaplriecseanctid, andvaryingamountsof 184 A.5. Summary of the chemical constituents and physical characteristics for BpoalTyie0th3yslleunrreiiemsinpere(pPaErIe)dwwiitthhou5t.b0i7nodeorxaplriecseanctid,andvaryingamountsof 185 viii LISTOFFIGURES Figure page 2.1. Productionflowchartforthefabricationofthemultilayercapacitor.'5' 9 2.2. Schematicshowingboththe3-dimensionalviewandtheside-viewofthe laminated polycrystalline ceramic and metal structure of the multilayer capacitor.**2' 10 2.3. Different types of rheological behavior characteristics for various suspensions. 13 2.4. TheoreticalphasestabilitydiagramfortheBa-Ti-C02-H20system.04'15' 17 2.5. ThetheoreticalstabilitydiagramforaqueousTi02suspensions.'54'55' 18 2.6. bSacrhiemuamtitictasnuatmem,arsipezciinfigcatlhleyprtoheblienmcsoansgsrouceinatteddiswsiotlhutaiqouneooufsBprao2c+esasnidngtohef formation of the Ti-rich and Ba-rich surface layer depicted in the correspondingparticlediagram.04,35' 19 2.7. Sstcrhuecmtaurtei.c022s1h'owing two different views of the BaTi03 perovskite 21 2.8. Aschematic ofthe various techniques with corresponding reactions to passivatemetalswhere(a)anoxidesurfacelayerformsinthepresenceof 0as2s,u(rbe)ctahatthotdhiecpgraoltveacntiiconcewlhlicmhakiensvoltvheespaipsealcirinfeictiahlemcaagthnoedsei,um(c)anaondoeditco protection which passivates through exposure ofthe metal to a highly concentratedoxidizingsolution,and (d)inhibitorionsassociate with the surfacetoprotecttheunderlyingmetalfromcorrosion.158' 23 2.9. Fivedifferenttypesofglasssurfacesproducedduringcorrosion.*59' 25 2.10.SCpae-cCia2t0i4o-nH2d0iasgyrsatmesm/f6o3r'64'(a) the Ba-C2O4-H20 system03'58' and (b) the 27 2.11 Theseparationdistance,d,betweenthetwopairsofparticlesisdetermined atthe initial interaction ofthe surrounding ionic clouds. The effective thicknessofthesurroundingioniccloud(diffuselayer)isthereciprocalof theDebye-Hiickelparameterwherethekvaluein(a)issmallerthan(b) 31 2.12.Thepotentialdistributionnearthesurfaceofaparticlefordifferentionic strengthvaluesforasimpleGouy-Chapmanmodelofthedoublelayer.'70' 32 ix 2.13.Theelectricaldoublelayerstructureshowingthe strongly adsorbed ions withintheSternplaneandthediffusesurroundingcloudofcounterionsthat decreasesinconcentrationwithdistancefromtheparticlesurface/68' 34 2.14.(a.) Aschematic showing the attractive, repulsive and total electrostatic interactionenergycurvesforaspecificsolutionconditions,and(b.)thetotal electrostatic interaction energy curves for apoorly dispersed system, a moderatelydispersedsystem,andawelldispersedsystem.'68,70' 35 2.15.Schematic showing a possible interaction between aqueous species, specificallyaPVA-Ba2+interaction/44'45' 37 2.16.Schematic showing two differentpolymeric dispersing mechanisms for suspensions,(a)depletiondispersionwherethepolymerremainsinsolution and prevents particle collisions and (b) adhesion of the cationic polyelectrolytetotheparticlesurfacepreventingparticle-particlecontactby bothpolymericandelectrostaticrepulsion/38' 39 2.17.e(aa)rtShucmamtiaornysaotf0t.h3e3mxob1i0"l3iMtycvosn.cpenHtrcautrivoens,f(obr)thEelercuttriolpehaotredtiifcfermeonbtilailtkyalvisn.e pH curves for rutile in the presence of different concentrations of Ba(N03)2.(7284' 41 2.18.PthaarttisclheowelsecvtarroipahtoiroensiinsldoatttaofloortvbaerhiaovuisorloatsswoefllcoamsmtehrecpiaolwdBearTsiu0p3plpioewr/d4e9'r 43 2.19.Elloeacdtirnogp/h4o9r'eticbehaviorforthreeBaTi03suspensions at different solids 44 2.20.BoththetheoreticalandexperimentalelectrophoreticbehaviorofCOMare illustratedandarelativelyconstantchargeisdepictedoverthepH range fromPH4topH10/64' 46 2.21.t(ao.)deStcehremmianteicthreepelreecsternotpihnogretthiecpamrotbiicllietmy,ove(bm.e)nTtheinealnecatprpolpiheodreetliecctmroicbifliietlyd canbeplottedasafunctionofpHorusedtocalculatethezetapotentialand plottedasafunctionofpH 52 2.22.Schematicshowingvariationsinthesedimentationofthesuspensions and thesedimentheightrecordedinthesedimentationanalysis. Fingershows variationsinthetransparencyofthesuspensions 55 2.23.Scanningelectronmicrographsoftheparticlepackingwithinthehandcast pseudo-tapesshowingthedifferencebetween(a.)gooddispersionand(b.) baddispersion 57 2.24.Schematicshowingthevariouscomponentsandmathematicalvariablesfor thecone/plateviscometerandthecorrespondingmathematicalexpressions todeterminetheshearstress,shearrate,andviscosity/105' 58 2.25.Aparstiucmlemsa,rwyatoefr,vaarnidopusoliynmteerraicctiaodndsittihvaetscantakeplacebetweentheBaTi03 60 x