Σύνθεση και φασματοσκοπικός χαρακτηρισμός λεπτών υμενίων που χρησιμοποιούνται σε κυψέλες καυσίμου στερεών οξειδίων (SOFCs)

Synthesis and Spectroscopic Characterization of Thin Films used for Solid Oxide Fuel Cells (SOFCs) (Αγγλική)

  1. MSc thesis
  2. Sapountzis, Antonios
  3. Κατάλυση και Προστασία του Περιβάλλοντος (ΚΠΠ)
  4. 22 Σεπτεμβρίου 2019 [2019-09-22]
  5. Αγγλικά
  6. 151
  7. Kontoyannis, Christos
  8. Kontoyannis, Christos | Sogomon, Bogosian
  9. Κυψέλες καυσίμου στερεών οξειδίων and Solid oxide fuel cells | Tεχνικές φασματοσκοπικού χαρακτηρισμού and Spectroscopic characterization techniques | Λεπτά υμένια and Thin films | Τεχνικές εναπόθεσης and Deposition techniques
  10. 153
  11. Fig. 1: Fuel cell market size for different types of fuel cells ............................................. 1 Fig. 2: Volume to energy density comparison between batteries and fuel cells ................ 2 Fig. 3: Schematic diagram of ion transport processes in a SOFC ..................................... 4 Fig. 4: Basic material schematic of a SOFC ...................................................................... 6 Fig. 5: Schematic of a typical sputtering system ............................................................... 8 Fig. 6: Schematic of a typical PLD system ...................................................................... 11 Fig. 7: Schematic of the EB-PVD working principle ...................................................... 15 Fig. 8: Schematic of a typical CVD system ..................................................................... 18 Fig. 9: Schematic of one ALD cycle ................................................................................ 20 Fig. 10: Schematic of a spray deposition system ........................................................... 24 Fig. 11: Schematic of an Electrostatic Spray Deposition system ................................... 25 Fig. 12: Schematic of a flame deposition system ........................................................... 28 Fig. 13: Schematic of a plasma spray deposition system ............................................... 29 Fig. 14: Schematic of an Ultrasonic Spray Pyrolysis ..................................................... 31 Fig. 15: Schematic of an electrophoretic deposition system .......................................... 35 Fig. 16: Schematic of a deposition cycle of the metal organic decomposition .............. 39 Fig. 17: Schematic of the colloidal impregnation phase ............................................... 39 Fig. 18: Schematic of the fabrication steps of the slurry-coating method ...................... 40 Fig. 19: Schematic of the fabrication steps for the sol-gel method ................................ 41 Fig. 20: Combination of spectroscopy techniques of a catalyst in situ conditions ........ 45 Fig. 21: A typical X-ray Photoelectron Spectrometry system ....................................... 46 Fig. 22: Typical XPS wide energy spectra of a gold surface ......................................... 47 Fig. 23: a) XPS spectra (4f electrons) of Pt, PtO and PtO 2 b) Atomic ratio of oxygen to platinum in the deposited film ............................................................................................. 48 Fig. 24: a) XPS wide spectrum of the SNC thin film ..................................................... 49 Fig. 25: XPS spectra of carbon 1s for ALD Pt thin films produced with 1s & 3s O 2 pulsing times ....................................................................................................................... 50 Fig. 26: XPS spectra of 28 & 63 nm YSZ thin films ..................................................... 51 Fig. 27: Depth profile XPS, atomic ratio of the YSZ/GDC thin film ............................ 51 Fig. 28: XPS spectra (Ag3d peaks) before and after operation (at 450 o C) of an Ag/YSZ modified cathode .................................................................................................. 52 Fig. 29: YSZ thin film's wide energy XPS spectra made by PE-ALD........................... 53 Fig. 30: High resolution (near Ce3d) XPS spectra of a cerium oxide thin film made by ALD .......................................................................................................................... 53 Fig. 31: High resolution XPS scan (near Ce3d) of ZrO 2 -doped CeO 2 thin films (ZDC), Ce1- 0 at.% Zr, Ce0.8 - 7.7 at.% Zr and Ce0.4 - 18.7 at.% Zr ............................................ 54 Fig. 32: Depth profile XPS for a) LNF64 thin film on GDC, b) LNF64 bulk sample. .. 55 Fig. 33: X-ray diffractometer ......................................................................................... 56 Fig. 34: XRD spectra of ZnO a) un-doped and Al-doped with different concentrations b) - 0.73 %, c) - 1.28 %, d) - 1.82 % ................................................................................... 57 Fig. 35: a) XRD peaks from the (111) & (200) plane of Pt thin films (200 nm, 600 o C annealing), b) relative (200 to 111) intensity in function with the O 2 content during reactive sputtering deposition ............................................................................................. 58 Fig. 36: XRD patterns of a NiO-YSZ film made by reactive sputtering before and after annealing at 900 o C ............................................................................................................. 59 Fig. 37: GI-XRD patterns of as deposited YSZ thin films (~100 nm) with different target O 2 poisoning. ............................................................................................................. 60 Fig. 38: XRD patterns of SNC thin films on YSZ substrates deposited by PLD at different temperatures (600, 700, 800 o C) ........................................................................... 61 Fig. 39: XRD patterns of YSZ thin films on NiO-YSZ substrates (at 500 o C) deposited by PLD with different oxygen partial pressures. ................................................................ 61 Fig. 40: XRD patterns of a BCFZY powder, a pellet and a thin film made by PLD ..... 62 Fig. 41: XRD patterns of a GSCO thin film deposited by PLD on a YSZ substrate at a) different temperatures and b) different oxygen partial pressures ........................................ 63 Fig. 42: XRD patterns of an alumina substrate, a bulk GDC sample and a GDC thin film deposited on a porous Pt supported on an alumina substrate ...................................... 63 Fig. 43: XRD pattern of an YSZ/SDC thin bi-layer made by PLD on a modified anode substrate .......................................................................................................................... 64 Fig. 44: XRD patterns of YSZ thin films a) bulk, b) on Pt (111), c) on Pt (200), d) on sapphire (0001) .................................................................................................................... 65 Fig. 45: XRD patterns of SDC thin films deposited by EB-PVD on SiO 2 substrates using different electron gun powers. ................................................................................... 66 Fig. 46: YSZ thin film XRD patterns as-deposited & annealed ..................................... 67 Fig. 47: XRD patterns of a BZCY thin film made by EB-PVD as deposited and sintered at different temperatures ..................................................................................................... 67 Fig. 48: YSZ's XRD patterns made by AA-CVD on a) silicon, b) sapphire substrate at different deposition temperatures ........................................................................................ 68 Fig. 49: XRD patterns of YSZ thin films A) 990 nm, B) 540 nm, C) 280 nm made by ALD on LSM substrates ...................................................................................................... 69 Fig. 50: XRD patterns of YSZ thin films made by a) PLD, b) ALD, c) Sputtering ...... 69 Fig. 51: XRD patterns of YSZ thin films made by ALD on Si (001) & on Pt/Ti- deposited Si (001) ............................................................................................................... 70 Fig. 52: XRD patterns of ALD & Sputtered YSZ thin films before & after annealing at 450 o C for 10 h .................................................................................................................... 71 Fig. 53: XRD patterns of ZrO 2 -doped CeO 2 thin films made by ALD .......................... 72 Fig. 54: XRD pattern of a tetragonal zirconia film made by ESD ................................. 72 Fig. 55: XRD patterns of ESD deposited CGO films on Stainless steel substrates as- deposited and post-annealed at different temperatures. ...................................................... 73 Fig. 56: XRD pattern of a YSZ thin film made by ESD on a Pt-deposited Si substrate 74 Fig. 57: XRD patterns of SDC thin films a) as deposited (at 400 o C) and b) post- annealing (at 700 o C) ........................................................................................................... 74 Fig. 58: XRD patterns of ESD-deposited LSM/YSZ films with different YSZ content (after annealing at 800 o C for 1 h) ....................................................................................... 75 Fig. 59: XRD patterns of SDC deposited films on stainless steel substrates at 350 o C and post-annealed at different temperatures for 2 h ............................................................ 76 Fig. 60: XRD patterns of ScSZ films, as deposited and after annealing at 600 o C & 700 o C .......................................................................................................................... 76 Fig. 61: Grazing incidence-XRD pattern of a YSZ thin film made by ESD on NiO- 8YSZ substrate followed by an 800 o C annealing for 2 h in air ......................................... 77 Fig. 62: XRD patterns of LSC thin films made by flame spray deposition on sapphire substrates followed by annealing at different temperatures for 10 h .................................. 78 Fig. 63: a) XRD patterns of CGO thin films as-deposited & annealed at different temperatures, b) (111)/(200) XRD peak ratio and CGO grain growth in function of the annealing temperature ......................................................................................................... 78 Fig. 64: XRD pattern of a LSM thin film made by aerosol flame spray ........................ 79 Fig. 65: XRD pattern of a La 2 O 3 using Ar/H 2 plasma spraying ..................................... 80 Fig. 66: XRD patterns of YSZ thin films produced by USP at 400 o C a) as-deposited, b) after thermal annealing at 500 o C ........................................................................................ 80 Fig. 67: XRD patterns of annealed LSCF-CGO thin films deposited on YSZ substrates by SP .......................................................................................................................... 81 Fig. 68: LSCF-CGO XRD patterns made by spray pyrolysis at 235 oC and further annealed at higher temperatures (700-900 o C for 4 h) ........................................................ 82 Fig. 69: XRD (111) peak of a GDC thin film deposited by spray pyrolysis on a Si substrate followed by annealing at different temperatures.................................................. 83 Fig. 70: XRD patterns of BCY films made by spray pyrolysis a) with different solution concentrations and annealed at 900 o C, b) 0.1M concentration and annealed at different temperatures ........................................................................................................................ 84 Fig. 71: XRD pattern of a LSCF thin film deposited by spray pyrolysis on Si substrate at 200 o C as-deposited and annealed at 750 o C ................................................................... 84 Fig. 72: XRD patterns of sprayed BCZY thin films as-deposited and annealed at different temperatures ......................................................................................................... 85 Fig. 73: XRD patterns of LSCF thin films made by spray pyrolysis at 450 o C with different Sr content (0 - 0.4 %) and annealed for 2 h at 500 o C .......................................... 85 Fig. 74: XRD patterns of SDC thin films made by USP on glass at different substrate temperatures ........................................................................................................................ 86 Fig. 75: XRD pattern of a NiO 60 % - YSZ 40 % thin film bi-layer made by EPD ...... 87 Fig. 76: XRD patterns of a YSZ thin film deposited by EPD on NiO-YSZ substrate, as- deposited and after a H 2 reduction at 800 o C ...................................................................... 88 Fig. 77: XRD pattern of a SDC film deposited by EPD on a stainless steel substrate ... 88 Fig. 78: XRD patterns of spin-coated YSZ thin films on Si substrates annealed at different temperatures ......................................................................................................... 89 Fig. 79: XRD patterns of LSCF powder material and a dip-coated LSCF/CGO cell .... 90 Fig. 80: XRD patterns of nano-web LSCF thin films annealed at different temperatures . .......................................................................................................................... 91 Fig. 81: XRD patterns of YSZ and GDC layers made by slurry spin coating ............... 91 Fig. 82: Scanning Electron Microscopy schematic ........................................................ 92 Fig. 83: Electron beam - material interactions schematic .............................................. 93 Fig. 84: EDS profile on the cross-section of a YSZ/GDC thin film .............................. 93 Fig. 85: BCFZY thin film made by PLD on Si substrate SEM images (a) cross section, (b) surface, (c) - (h) EDS images of Ba, Co, Fe, Zr, Y, O, respectively .......................... 94 Fig. 86: Cross-section depth EDS scan of a YSZ - SDC film made by PLD (left to right) .......................................................................................................................... 95 Fig. 87: EDS spectra of a YSZ thin film deposited on a NiO-YSZ substrate by EB-PVD .......................................................................................................................... 96 Fig. 88: EDS spectra of a YSZ thin film made by ALD on a LSM substrate. ............... 96 Fig. 89: EDS spectra of a tetragonal YSZ thin film deposited by EDS on a stainless steel substrate ...................................................................................................................... 97 Fig. 90: EDS spectra of a La 1-x Sr x Co 1-y Fe y O 3 thin film deposited by ESD on a stainless steel at 300 o C followed by an annealing step at 900 o C for 2 h ......................................... 98 Fig. 91: EDS spectrum (15 kV) of a CGO thin film deposited by ESD on a stainless steel substrate at 260 o C followed by an 900 o C annealing step ......................................... 98 Fig. 92: EDS spectrum of LaMnO 3 splats created by plasma spraying ......................... 99 Fig. 93: EDS spectrum of a CGO thin film made by plasma spaying ........................... 99 Fig. 94: EDS spectrum of a) a BCZY thin film and b) a BCY thin film annealed at 1000 o C ........................................................................................................................ 100 Fig. 95: EDS line scan analysis of a) a LSF/YSZ bilayer , b) a LSF/YSZ bilayer with a CGO barrier layer .............................................................................................................. 100 Fig. 96: EDS spectrum of a SDC thin film made by ultrasonic spray pyrolysis .......... 101 Fig. 97: Elemental content of a YSZ / NiO-YSZ bi-layer cross-section analyzed by EDS ........................................................................................................................ 101 Fig. 98: EDS spectrum of a LNF thin film made by spin-coating method on a GDC substrate ........................................................................................................................ 102 Fig. 99: Schematic of the Raman spectrometer ............................................................ 103 Fig. 100: Raman spectrum of a tetragonal zirconia (2 mol.% Y 2 O 3 ) made by ESD ...... 104 Fig. 101: Raman spectra of a) a YSZ precursor powder, b) a YSZ plasma sprayed thin film ........................................................................................................................ 104 Fig. 102: Raman spectra of a BCY thin film made by spray pyrolysis technique (0.1M concentration solution and 900 o C post-annealing) .......................................................... 105 Fig. 103: Raman spectra of a BCY and a BCZY films made by spray deposition followed by an 1000 o C annealing step ............................................................................. 106 Fig. 104: Schematic representation of the working principle of a FTIR spectrometer .. 107 Fig. 105: FTIR spectra of A) a Si substrate, B) a SrCO 3 film, C) the as-deposited SrCoO thin film, D) the SrCoO 3-δ thin film annealed at 700 o C in nitrogen for 15 min ... 108 Fig. 106: FTIR spectra of BCY thin films, as-deposited and post annealing at 900 o C 108 Fig. 107: FTIR spectra of YSZ powder material a) S1, b) S2, c) S3 ............................. 109 Fig. 108: FTIR spectra of a calcined (at 600 o C) YSZ precursor powder used in EPD . 110 Fig. 109: Illustration of an Atomic Force Microscope ................................................... 112 Fig. 110: 3D AFM image of a SNC thin film on YSZ (followed by annealing at 700 o C for 30 min) ........................................................................................................................ 113 Fig. 111: AFM topography images of a pure GDC and a 63 nm thick YSZ film on GDC as deposited and after annealing at 1200 o C for 5 h. The figures represent the RMS roughness values. .............................................................................................................. 113 Fig. 112: AFM topography images of (a) a YSZ sputtered layer, (b) a YSZ layer made by ALD ..................................................................................................................... 114 Fig. 113: AFM roughness measurements of CGO films made by flame spray, as deposited (left) and after an annealing step at 1200 o C for 10 h (right) ............................ 114 Fig. 114: AFM images a) 2D, b) 3D of a CeO 2 thin film deposited by flame spray on glass substrates .................................................................................................................. 115 Fig. 115: Morphological study of the surface of spray deposited BCY and BCZY thin films (0.1M concentration & 1000 o C annealing temp.) using AFM ............................... 116 Fig. 116: Illustration of the TEM components ............................................................... 117 Fig. 117: TEM cross-section images of a Ca 3 Co 4 O 9+δ film deposited by PLD on a sapphire Al 2 O 3 - (0001) substrate ...................................................................................... 118 Fig. 118: HR-TEM images of (a) a pure Ag, (b) an Ag-GDC0.5, (c) an Ag-GDC1 and (d) an Ag-GDC5, surface .................................................................................................. 118 Fig. 119: HRTEM images of an 180 nm thick YSZ film (4:1) made by ALD between Pt sputtered electrodes ....................................................................................................... 119 Fig. 120: (a) cross section TEM image of a fuel cell with a CeO 2 interlayer after 24 h operation at 450 o C, (b) zoomed-in image near the CeO 2 -YSZ interface. ........................ 119 Fig. 121: Dark field cross-section TEM images of 59LSCF-41CGO thin film cathodes annealed at different temperatures (600, 700, 850 o C) ...................................................... 120 Fig. 122: A HR-TEM image showing the pores of a nano-structured CGO thin film prepared by sol-gel method ............................................................................................... 120 Fig. 123: Focused Ion Beam schematic ......................................................................... 121 Fig. 124: Cross section SEM images of a YSZ thin film layer made by reactive sputtering, a) without bias, b) -0.1 W∙cm -2 , c) -0.3 W∙cm -2 , d) -0.5 W∙cm -2 ..................... 122 Fig. 125: SEM images of (a) the porous NiO/YSZ substrate, YSZ thin films made by impulse magnetron sputtering at different pressures: (b) 270 mPa, (c) 750 mPa ............. 123 Fig. 126: SEM cross-section images of YSZ thin films deposited by PLD on NiO/YSZ substrates, a) without micro-defects and b) with micro-defects ....................................... 123 Fig. 127: FE-SEM images of the NiO-YSZ anode substrate A) after pre-sintering to 1100 o C (3 h) and B) after EB-PVD YSZ coating & sintering to 1400 o C (3 h) .............. 124 Fig. 128: SEM images of (left) the surface and (right) the cross-section of YSZ thin films deposited by PLD on (a) Pt (111), (b) Pt (200) and (c) sapphire (0001) substrates 125 Fig. 129: Cross-section SEM images of SOFCs. The YSZ electrolyte was made by (a) DC sputtering, (b) ALD, (c) DC sputtering + ALD .......................................................... 125 Fig. 130: SEM image of a La 1-x Sr x Co 1-y Fe y O 3 thin film deposited by ESD on a CGO substrate ........................................................................................................................ 126 Fig. 131: Cross-section SEM images of YSZ films deposited by EPD on porous NiO- YSZ substrates using and intermediate graphite layer, (a) before and (b) after co-firing (bar = 5 μm) ..................................................................................................................... 126 Fig. 132: SEM cross-section image of a SOFC made by slurry spin coating method after an electrochemical test .............................................................................................. 127 List of Tables Table 1: Elemental stoichiometry of a SDC powder and the SDC thin films evaporated with different deposition rates. ............................................................................................ 95 Table 2: Average roughness (Ra) of a YSZ substrate and of the spray deposited LSCF- CGO thin films .................................................................................................................. 115 Table 3: Summary of the main deposition techniques for materials used in SOFC applications ....................................................................................................................... 129 Table 4: Summary of the main spectroscopic characterization techniques for materials used in SOFC applications ................................................................................................ 130 Table 5: Summary of the main microscopy characterization techniques for materials used in SOFC applications ................................................................................................ 131
    • ΑΝΑΒΟΛΗ ΑΝΑΡΤΗΣΗΣ ΗΛ. ΑΡΧΕΙΟΥ ΕΩΣ ΤΟΝ 9/2022. Οι κυψέλες καυσίμου στερεού ηλεκτρολύτη (SOFC) μπορούν να αποδειχθούν ζωτικής σημασίας για τα επόμενα χρόνια, καθώς οι κοινωνίες αναζητούν λύσεις για τις υψηλότερες παγκόσμιες απαιτήσεις σε ενέργεια, όμως μειώνοντας παράλληλα την εξάρτηση από τα ορυκτά καύσιμα για την παραγωγή ενέργειας. Η κυψέλη καυσίμου στερεού ηλεκτρολύτη είναι μια από τις κυψέλες καυσίμου που λειτουργούν σε υψηλότερες θερμοκρασίες και έχουν ευρύ φάσμα εφαρμογών για μελλοντικά συστήματα παραγωγής ενέργειας με αμελητέα συμβολή στη ατμοσφαιρική ρύπανση. Τα λεπτά υμένια παίζουν βασικό ρόλο στην περαιτέρω ανάπτυξη και επίλυση των σημερινών προβλημάτων των SOFC, όπως η υψηλή θερμοκρασία λειτουργίας, η οποία οδηγεί σε καταπόνηση των υλικών του SOFC, κακή στεγανότητα της κυψέλης, αυξημένη αντίσταση και γενικά χαμηλότερη απόδοση των κυψέλων. Με την αντικατάσταση των παχύτερων μεμβρανών που χρησιμοποιούνται στα SOFC από λεπτά υμένια (στην κλίμακα του νανόμετρου) μπορούν να βελτιωθούν αρκετά χαρακτηριστικά των κυψέλων χωρίς όμως να επηρεαστούν οι μηχανικές ιδιότητες της κυψέλης. Καθώς κάθε τμήμα της κυψέλης πρέπει να πληροί ορισμένες προδιαγραφές, οι επιφανειακές αλληλεπιδράσεις μεταξύ αυτών των τμημάτων μπορεί να έχουν αρνητική επίδραση στην λειτουργία των SOFC. Τα λεπτά υμένια μπορούν να χρησιμοποιηθούν ως μεταβατικά στρώματα, βελτιώνοντας την τραχύτητα, μειώνοντας την ανάμειξη υλικών, εξαλείφοντας τις διαρροές, κλπ. Στην παρούσα διπλωματική εργασία περιγράφονται αρκετές τεχνικές εναπόθεσης λεπτών υμενίων, καθώς και τα νεότερα ερευνητικά αποτελέσματα για κάθε εφαρμογή. Καθώς η τεχνολογία των SOFC αναπτύσσεται διαρκώς, η ανάγκη για ανάπτυξη και χρήση αντίστοιχων τεχνικών χαρακτηρισμού των λεπτών υμενίων αυξάνεται επίσης. Τυπικά, κάθε τεχνική εξειδικεύεται σε μια ομάδα ιδιοτήτων αυτών των υλικών (επιφάνεια, δεσμοί, κρυσταλλογραφία κ.λπ.). Σε αυτή τη μελέτη παρουσιάζονται διάφορες τεχνικές φασματοσκοπικού χαρακτηρισμού και τεχνικές μικροσκοπίας καθώς και οι πληροφορίες που λαμβάνονται από τα διάφορα λεπτά υμένια που χρησιμοποιούνται στα SOFC. Τέλος, θα παρουσιαστούν οι περιορισμοί αυτών των τεχνικών που χρησιμοποιούνται για τη σύνθεση και το χαρακτηρισμό των λεπτών υμενίων καθώς και προτάσεις για πιθανές μελλοντικές βελτιώσεις.
    • Solid oxide fuel cells (SOFCs) can be a key technology over the next years, as societies are trying to solve higher worldwide energy demands while reducing the dependency on fossil fuels for energy production. The solid oxide fuel cell is one of the fuel cell types operating at higher temperatures and having a wide range of application for future energy production systems with negligible contribution to pollution. Thin films are playing a key role in further developing and solving current issues of the SOFCs such as high operation temperature, which leads to SOFC material degradation, poor cell leak tightness, increased resistivity and generally lower cell performance. Thin films - typically at a nanometer scale - can offer better properties than the thicker films currently used in SOFCs without influencing the mechanical properties of the cell. As each cell component must meet certain requirements, adhesion issues or other surface interactions can frequently arise between the components. Thin films can be also used as a surface modification / transition layers; for instance for improving roughness, reducing material intermixing, eliminating leaks in a cell, etc. In this diploma thesis several thin film deposition techniques are being described including recent research applications and advancements for the SOFCs. As the development of the thin film technology is ongoing, the need of characterization techniques is growing as well. Typically each technique is specialized in one area of material properties (surface, bonds, crystallography, etc). In this study, several spectroscopic and microscope characterization techniques and the obtained information from various thin films used in SOFCs are being presented. Lastly, investigations describing the limitations of the currently used techniques for synthesis and characterization of thin films are being presented and suggestions on potential future improvements are made.
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