Non-stoichiometric perovskite oxides have been studied as a new family of redox oxides for solar thermochemical hydrogen (STCH) production owing to their favourable thermodynamic properties. However, conventional perovskite oxides suffer from limited phase stability and kinetic properties, and poor cyclability. Here, we report a strategy of introducing A-site multi-principal-component mixing to develop a high-entropy perovskite oxide, (La1/6Pr1/6Nd1/6Gd1/6Sr1/6Ba1/6)MnO3 (LPNGSB_Mn), which shows desirable thermodynamic and kinetics properties as well as excellent phase stability and cycling durability. LPNGSB_Mn exhibits enhanced hydrogen production (?77.5 mmol moloxide?1) compared to (La2/3Sr1/3)MnO3 (?53.5 mmol moloxide?1) in a short 1 hour redox duration and high STCH and phase stability for 50 cycles. LPNGSB_Mn possesses a moderate enthalpy of reduction (252.51-296.32 kJ (mol O)?1), a high entropy of reduction (126.95-168.85 J (mol O)?1 K?1), and fast surface oxygen exchange kinetics. All A-site cations do not show observable valence changes during the reduction and oxidation processes. This research preliminarily explores the use of one A-site high-entropy perovskite oxide for STCH.
We present a graph neural network approach that fully automates the prediction of defect formation enthalpies for any crystallographic site from the ideal crystal structure, without the need to create defected atomic structure models as input. Here we used density functional theory reference data for vacancy defects in oxides, to train a defect graph neural network (dGNN) model that replaces the density functional theory supercell relaxations otherwise required for each symmetrically unique crystal site. Interfaced with thermodynamic calculations of reduction entropies and associated free energies, the dGNN model is applied to the screening of oxides in the Materials Project database, connecting the zero-kelvin defect enthalpies to high-temperature process conditions relevant for solar thermochemical hydrogen production and other energy applications. The dGNN approach is applicable to arbitrary structures with an accuracy limited principally by the amount and diversity of the training data, and it is generalizable to other defect types and advanced graph convolution architectures. It will help to tackle future materials discovery problems in clean energy and beyond.
Wexler, Robert B.; Sai Gautam, Gopalakrishnan; Bell, Robert T.; Shulda, Sarah; Strange, Nicholas A.; Trindell, Jamie T.; Sugar, Joshua D.; Nygren, Eli; Sainio, Sami; Mcdaniel, Anthony H.; Ginley, David; Carter, Emily A.; Stechel, Ellen B.
Modeling-driven design of redox-active off-stoichiometric oxides for solar thermochemical H2 production (STCH) seldom has resulted in empirical demonstration of competitive materials. We report the theoretical prediction and experimental evidence that the perovskite Ca2/3Ce1/3Ti1/3Mn2/3O3 is synthesizable with high phase purity, stable, and has desirable redox thermodynamics for STCH, with a predicted average neutral oxygen vacancy (VO) formation energy, Ev = 3.30 eV. Flow reactor experiments suggest potentially comparable or greater H2 production capacity than recent promising Sr-La-Mn-Al and Ba-Ce-Mn metal oxide perovskites. Utilizing quantum-based modeling of a solid solution on both A and B sub-lattices, we predict the impact of nearest-neighbor composition on Ev and determine that A-site Ce4+ reduction dominates the redox-activity of Ca2/3Ce1/3Ti1/3Mn2/3O3. X-ray absorption spectroscopy measurements provide evidence that supports these predictions and reversible Ce4+-to-Ce3+ reduction. Our models predict that Ce4+ reduces even when it is not nearest-neighbor to the VO, suggesting that refinement of Ce stoichiometry has the possibility of further enhancing performance.
In this report, we investigate the thermal reduction of the octahedral perovskite BaCe0.25Mn0.75O3(BCM) using in situ electron energy loss spectroscopy (EELS) in an aberration-corrected transmission electron microscope (TEM). The 12R-polytype of BCM is known to demonstrate high solar thermochemical hydrogen production capacity. In situ EELS measurements show that Mn is the active redox cation in BCM, undergoing thermal reduction from Mn4+to Mn3+during heating to 700 °C inside the TEM under a high vacuum. The progressive reduction of Mn4+during oxygen vacancy (Ov) formation was monitored as a function of temperature. Additionally, atomic-resolution scanning transmission electron microscopy identified two different types of twin boundaries present in the oxidized and reduced form of 12R-BCM, respectively. These two types of twin boundaries were shown, via computational modeling, to modulate the site-specific Ovformation energies in 12R-BCM. It is concluded that these types of atomic defects provide sites more energetically favorable for Ovformation during thermal reduction.
Sandia National Laboratories in collaboration with the National Renewable Energy Laboratory outline a framework for developing a solar fuels roadmap based on novel concepts for hybridizing gas-splitting thermochemical cycle s with high-temperature electro chemical steps. We call this concept SoHyTEC, a Solar Hybrid Thermochemical-Electrochemical Cycle. The strategy focuses on transforming purely thermochemical cycles that split water (H2O) and carbon dioxide (CO2) to produce hydrogen (H 2 ) and carbon monoxide (CO) , respectively, the fundamental chemical building blocks for diverse fuels and chemicals , by substituting thermochemical reactions with high-temperature electrochemical steps. By invoking high-temperature electrochemistry, the energy required to complete the gas-splitting cycle is divided into a thermal component (process temperature) and an electrical component (applied voltage). These components, sourced from solar energy, are independently variable knobs to maximize overall process efficiency. Furthermore, a small applied voltage can reduce cycle process temperature by hundreds of degrees , opening the door to cost-effective solar concentrators and practical receiver/reactor de signs. Using the SoHyTEC concept as a backdrop, we outline a framework that advocates developing methods for automating information gathering, critically evaluating thermochemical cycles for adapting into SoHyTEC, establishing requirements based on thermodynamic analysis, and developing a model-based approach to benchmarking a SoHyTEC system against a baseline concentrating solar thermal integrated electrolysis plant. We feel these framework elements are a necessary precursor to creating a robust and adaptive technology development roadmap for producing solar fuels using SoHyTEC. In one example, we introduce high-temperature electrochemistry as a method to manipulate a fully stoichiometric two-step metal oxide cycle that circumvents costly separation processes and ultra-high cycle temperatures. We also identify and group water-splitting chemistries that are conceptually amenable to hybridization.
Understanding hydrogen incorporation into palladium requires detailed knowledge of surface and subsurface structure and atomic interactions as surface hydrogen is being embedded. Using density functional theory (DFT), we examine the energies of hydrogen layers of varying coverage adsorbed on Pd(111). Here we find that H–H and H–Pd interactions promote the formation of the well-known ($\sqrt{3}$ x $\sqrt{3}$) phases but also favor an unreported (3 × 3) phase at high H coverages for which we present experimental evidence. We relate the stability of isolated H vacancies of the (3 × 3) phase to the need of H2 molecules to access bare Pd before they can dissociate. Following higher hydrogen dosage, we observe initial steps of hydride formation, starting with small clusters of subsurface hydrogen. The interaction between H and Pd is complicated by the persistent presence of carbon at the surface. X-ray photoelectron spectroscopy experiments show that trace amounts of carbon, emerging from the Pd bulk despite many surface cleaning cycles, become mobile enough to repopulate the C-depleted surface at temperatures above 200 K. When exposed to hydrogen, these surface carbon atoms react to form benzene, as evidenced by scanning tunneling microscopy observations interpreted with DFT.
Solar thermochemical hydrogen (STCH) production is a promising method to generate carbon neutral fuels by splitting water utilizing metal oxide materials and concentrated solar energy. The discovery of materials with enhanced water-splitting performance is critical for STCH to play a major role in the emerging renewable energy portfolio. While perovskite materials have been the focus of many recent efforts, materials screening can be time consuming due to the myriad chemical compositions possible. This can be greatly accelerated through computationally screening materials parameters including oxygen vacancy formation energy, phase stability, and electron effective mass. In this work, the perovskite Gd0.5La0.5Co0.5Fe0.5O3 (GLCF), was computationally determined to be a potential water splitter, and its activity was experimentally demonstrated. During water splitting tests with a thermal reduction temperature of 1,350°C, hydrogen yields of 101 μmol/g and 141 μmol/g were obtained at re-oxidation temperatures of 850 and 1,000°C, respectively, with increasing production observed during subsequent cycles. This is a significant improvement from similar compounds studied before (La0.6Sr0.4Co0.2Fe0.8O3 and LaFe0.75Co0.25O3) that suffer from performance degradation with subsequent cycles. Confirmed with high temperature x-ray diffraction (HT-XRD) patterns under inert and oxidizing atmosphere, the GLCF mainly maintained its phase while some decomposition to Gd2-xLaxO3 was observed.
One promising method for solar energy storage is Solar Thermochemical Hydrogen (STCH) production. This two-step thermochemical process utilizes nonstoichiometric metal oxides to convert solar energy into hydrogen gas. The oxide first undergoes reduction via exposure to heat generated from concentrated solar power. When subsequently exposed to steam, the reduced oxide splits water molecules through its re-oxidation process, thus producing hydrogen gas. The viability of STCH depends on identifying redox-active materials that have fast redox kinetics, structural stability and low reduction temperatures. Complex perovskite oxides show promise for more efficient hydrogen production at lower reduction temperatures than current materials. In this work, a stagnation flow reactor was used to characterize the water splitting capabilities of BaCe0.25Mn0.75O3(BCM). In the future, the method outlined will be used to characterize structural analogues of BCM, to provide insight into the effect of material composition on water splitting behavior and ultimately guide the synthesis of more efficient STCH materials.
Ruddlesden–Popper (layered perovskite) phases are attracting significant interest because of their unique potential for many applications requiring mixed ionic and electronic conductivity. Here we report a new, previously undiscovered layered perovskite of composition, CexSr2–xMnO4 (x = 0.1, 0.2, and 0.3). Furthermore, we demonstrate that this new system is suitable for solar thermochemical hydrogen production (STCH). Synchrotron radiation X-ray diffraction and transmission electron microscopy are performed to characterize this new system. Density functional theory calculations of phase stability and oxygen vacancy formation energy (1.76, 2.24, and 2.66 eV/O atom, respectively with increasing Ce content) reinforce the potential of this phase for STCH application. Experimental hydrogen production results show that this materials system produces 2–3 times more hydrogen than the benchmark STCH oxide ceria at a reduction temperature of 1400 °C and an oxidation temperature of 1000 °C.
Overall objectives of the project are: Develop a science & engineering basis for the release, ignition, and combustion behavior of hydrogen across its range of use (including high pressure and cryogenic); and, Facilitate the assessment of the safety (risk) of hydrogen systems and enable use of that information for revising regulations, codes, and standards (RCS), and permitting hydrogen fueling stations.
Solar thermochemical hydrogen (STCH) production is one avenue for converting sunlight into hydrogen through concentrating solar thermal technology. STCH is a two-step redox process that begins with concentrated sunlight to thermally reduce a metal oxide around 1500 °C leaving it in an oxygen deficient form. Subsequent exposure of the reduced metal oxide to steam at lower temperature reoxidizes the material and produces hydrogen. The efficiency of this process is dependent on the metal oxide material thermodynamic properties and cycle operating conditions.
Singh, Abhishek; Lapp, Justin; Grobbel, Johannes; Reinhold, Jan P.; Olivera, Lamark; Ermanoski, Ivan; Siegel, Nathan P.; Mcdaniel, Anthony H.; Roeb, Martin; Sattler, Christian
Recently a novel design concept of a reactor—the cascading pressure reactor—for the thermochemical fuel production, using a solar-driven redox cycle, was proposed. In this concept, thermal reduction of metal oxide particles is completed in multiple stages, at successively lower pressures. This leads to an order of magnitude decrease in the pumping power demand as compared to a single stage, which in turn increases the solar to fuel efficiency. An important step in the process is the transfer of heat in the form of concentrated solar radiation to the particles, while providing reducing conditions in the space surrounding the particles. In this context, a novel system for heating and reducing particles, with a focus on operating at the small prototype scale (below 20 kW), is investigated. The key goals of the system are continuous operation, uniform heating of the reactive material, the ability to heat reactive material to 1723 K or higher, and flexibility of control. These criteria have led to the conceptual design of a continuous thin-layer particle conveyor, contained in an apertured, windowed cavity and enclosed in a vacuum chamber. This chamber, in combination with a water-splitting chamber and other system components, allows the possibility of testing multiple redox materials without any significant change in the reactor design. The present work shows a potential design for the proposed component, feasibility tests of the physics of moving particles with relevant materials, and series of interconnected numerical models and calculations that can be used to size such a system for the appropriate scales of power and mass flow rates. The use of a unified design strategy has led to efficient development of the system. Experimental investigations of the horizontal motion plate allowed effective determination of motion profiles and bed uniformity. The most important factors determined through the modeling effort were the aperture diameter, which serves as the coupling point between the solar simulator lamp array and the cavity particle heating, and the particle bed thickness, which has a strong effect on the outlet temperature of the particles.
This research and development project is focused on the advancement of a technology that produces hydrogen at a cost that is competitive with fossil-based fuels for transportation. A twostep, solar-driven WS thermochemical cycle is theoretically capable of achieving an STH conversion ratio that exceeds the DOE target of 26% at a scale large enough to support an industrialized economy [1]. The challenge is to transition this technology from the laboratory to the marketplace and produce hydrogen at a cost that meets or exceeds DOE targets.
In this paper, we offer a perspective on the current state of material research in a part of the solar fuels community that exploits process heat derived from concentrated solar energy to power simple thermochemical gas-splitting cycles. The working fluid in this process is a nonstoichiometric oxide subject to extreme conditions that repeatedly distorts the lattice by forcing oxygen atoms to move in and out of the crystal. This technology is currently challenged by a need to discover optimal materials and derive robust processes to increase cycle efficiency. In the realm of emerging technologies for converting solar insulation to portable and storable energy carriers, this approach has already proven to be scalable with demonstrations that approach 100 kW. Innovations in materials and methods are required to increase solar utilization and process efficiency in order to achieve commercial viability.
Mcdaniel, Anthony H.; Ermanoski, Ivan; Stechell, Ellen; Johnson, Nathan; Siegel, Nathan; Hayre, Michael'; Sanders, Michael; Wolverton, Christopher; Chueh, William
Overall objectives of the project were: Verify the potential for solar thermochemical cycles for hydrogen production to be competitive in the long term and by 2020, develop this technology to produce hydrogen with a projected cost of $3.00/gge at the plant gate; and, Develop a high-efficiency particle bed reactor for producing hydrogen via a thermochemical water-splitting (WS) cycle, and demonstrate eight continuous hours of operation on a solar simulator producing greater than 3 L of H2.
The surface chemical capacitance of ceria and SDC was investigated using in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) in H2 H 2O environments at elevated temperatures. The spectra were collected in situ after equilibrating the samples under oxygen chemical potentials spanning -2.95 and -3.44 eV versus 1 atm O2. Consequently, the volumetric chemical capacitance of the surface, in the range of 103-104Fcm-3, is nearly two orders of magnitude larger than that of the bulk. Addition of Sm leads to a slight decrease of surface Ce3+ concentration, but a 10-fold enhancement in the surface capacitance under H2 H 2O atmospheres. Our hypothesis for this observation is that Sm lowers defect interactions. The areal surface capacitance calculated for SDC is in good agreement with literature values extrapolated from electrochemical measurements.
Recent work regarding the efficiency maximization for solar thermochemical fuel production in two step cycles has led to the design of a new type of reactor - the cascading pressure reactor - in which the thermal reduction step of the cycle is completed in multiple stages, at successively lower pressures. This approach enables lower thermal reduction pressures than in single-staged reactors, and decreases required pump work, leading to increased solar to fuel efficiencies. Here we report on the design and construction of a prototype cascading pressure reactor and testing of some of the key components. We especially focus on the technical challenges particular to the design, and their solutions.
Preparation of sodium zirconium silicate phosphate (NaSICon), Na1+ xZr2SixP3− xO12(0.25 ≤ x ≤ 1.0), thin films has been investigated via a chemical solution approach on platinized silicon substrates. Increasing the silicon content resulted in a reduction in the crystallite size and a reduction in the measured ionic conductivity. Processing temperature was also found to affect microstructure and ionic conductivity with higher processing temperatures resulting in larger crystallite sizes and higher ionic conductivities. The highest room temperature sodium ion conductivity was measured for an x = 0.25 composition at 2.3 × 10−5 S/cm. The decreasing ionic conductivity trends with increasing silicon content and decreasing processing temperature are consistent with grain boundary and defect scattering of conducting ions.
Next generation metal-ion conducting membranes are key to developing energy storage and utilization technologies like batteries and fuel ce lls. Sodium super-ionic conductors (aka NaSICON) are a class of compounds with AM 1 M 2 (PO 4 ) 3 stoichiometry where the choice of "A" and "M" cation varies widely. This report, which de scribes substitutional derivatives of NZP (NaZr 2 P 3 O 12 ), summarizes the accomplishments of a Laboratory D irected Research and Development (LDRD) project to analyze transport mec hanisms using a combination of in situ studies of structure, composition, and bonding, com bined with first principles theory and modeling. We developed an experimental platform and applied methods, such as synchrotron- based X-ray spectroscopies, to probe the electronic structure of compositionally well-controlled NaSICON films while in operation ( i.e ., conducting Na ions exposed to oxygen or water va por atmospheres). First principles theory and modeling were used to interpret the experimental observations and develop an enhanced understanding of atomistic processes that give rise to, and affect, ion conduction.
This report documents work that was performed under the Laboratory Directed Research and Development project, Science of Battery Degradation. The focus of this work was on the creation of new experimental and theoretical approaches to understand atomistic mechanisms of degradation in battery electrodes that result in loss of electrical energy storage capacity. Several unique approaches were developed during the course of the project, including the invention of a technique based on ultramicrotoming to cross-section commercial scale battery electrodes, the demonstration of scanning transmission x-ray microscopy (STXM) to probe lithium transport mechanisms within Li-ion battery electrodes, the creation of in-situ liquid cells to observe electrochemical reactions in real-time using both transmission electron microscopy (TEM) and STXM, the creation of an in-situ optical cell utilizing Raman spectroscopy and the application of the cell for analyzing redox flow batteries, the invention of an approach for performing ab initio simulation of electrochemical reactions under potential control and its application for the study of electrolyte degradation, and the development of an electrochemical entropy technique combined with x-ray based structural measurements for understanding origins of battery degradation. These approaches led to a number of scientific discoveries. Using STXM we learned that lithium iron phosphate battery cathodes display unexpected behavior during lithiation wherein lithium transport is controlled by nucleation of a lithiated phase, leading to high heterogeneity in lithium content at each particle and a surprising invariance of local current density with the overall electrode charging current. We discovered using in-situ transmission electron microscopy that there is a size limit to lithiation of silicon anode particles above which particle fracture controls electrode degradation. From electrochemical entropy measurements, we discovered that entropy changes little with degradation but the origin of degradation in cathodes is kinetic in nature, i.e. lower rate cycling recovers lost capacity. Finally, our modeling of electrode-electrolyte interfaces revealed that electrolyte degradation may occur by either a single or double electron transfer process depending on thickness of the solid-electrolyte-interphase layer, and this cross-over can be modeled and predicted.
This research and development project is focused on the advancement of a technology that produces hydrogen at a cost that is competitive with fossil-based fuels for transportation.
Despite rapid progress, solar thermochemistry remains high risk; improvements in both active materials and reactor systems are needed. This claim is supported by studies conducted both prior to and as part of this project. Materials offer a particular large opportunity space as, until recently, very little effort apart from basic thermodynamic analysis was extended towards understanding this most fundamental component of a metal oxide thermochemical cycle. Without this knowledge, system design was hampered, but more importantly, advances in these crucial materials were rare and resulted more from intuition rather than detailed insight. As a result, only two basic families of potentially viable solid materials have been widely considered, each of which has significant challenges. Recent efforts towards applying an increased level of scientific rigor to the study of thermochemical materials have provided a much needed framework and insights toward developing the next generation of highly improved thermochemically active materials. The primary goal of this project was to apply this hard-won knowledge to rapidly advance the field of thermochemistry to produce a material within 2 years that is capable of yielding CO from CO2 at a 12.5 % reactor efficiency. Three principal approaches spanning a range of risk and potential rewards were pursued: modification of known materials, structuring known materials, and identifying/developing new materials for the application. A newly developed best-of-class material produces more fuel (9x more H2, 6x more CO) under milder conditions than the previous state of the art. Analyses of thermochemical reactor and system efficiencies and economics were performed and a new hybrid concept was reported. The larger case for solar fuels was also further refined and documented.
The increasing global appetite for energy within the transportation sector will inevitably result in the combustion of more fossil fuel. A renewable-derived approach to carbon-neutral synthetic fuels is therefore needed to offset the negative impacts of this trend, which include climate change. In this communication we report the use of nonstoichiometric perovskite oxides in two-step, solar-thermochemical water or carbon dioxide splitting cycles. We find that LaAlO3 doped with Mn and Sr will efficiently split both gases. Moreover the H2 yields are 9× greater, and the CO yields 6× greater, than those produced by the current state-of-the-art material, ceria, when reduced at 1350 °C and re-oxidized at 1000 °C. The temperature at which O2 begins to evolve from the perovskite is fully 300 °C below that of ceria. The materials are also very robust, maintaining their redox activity over at least 80 CO2 splitting cycles. This discovery has profound implications for the development of concentrated solar fuel technologies.
Thermochemical cycles that divide the energetically unfavorable thermolysis of water or carbon dioxide into two or more reactions were used for solar driven fuel production. A large number of diverse metal oxides have been proposed for solar thermochemical fuel production (STFP) including stoichiometric compounds such as ferrites and other transition metal spinels. The design parameter is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. Operating temperature window is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. In the absence of kinetic data, however, it can be stated that achieving high average annual solar-to-fuel efficiencies (AASFE) requires that energy consumption of the reactions, and hence the reaction rates, be matched to the solar flux entering the system.
Two of the most daunting problems facing humankind in the twenty-first century are energy security and climate change. This report summarizes work accomplished towards addressing these problems through the execution of a Grand Challenge LDRD project (FY09-11). The vision of Sunshine to Petrol is captured in one deceptively simple chemical equation: Solar Energy + xCO2 + (x+1)H2O → CxH2x+2(liquid fuel) + (1.5x+.5)O2 Practical implementation of this equation may seem far-fetched, since it effectively describes the use of solar energy to reverse combustion. However, it is also representative of the photosynthetic processes responsible for much of life on earth and, as such, summarizes the biomass approach to fuels production. It is our contention that an alternative approach, one that is not limited by efficiency of photosynthesis and more directly leads to a liquid fuel, is desirable. The development of a process that efficiently, cost effectively, and sustainably reenergizes thermodynamically spent feedstocks to create reactive fuel intermediates would be an unparalleled achievement and is the key challenge that must be surmounted to solve the intertwined problems of accelerating energy demand and climate change. We proposed that the direct thermochemical conversion of CO2 and H2O to CO and H2, which are the universal building blocks for synthetic fuels, serve as the basis for this revolutionary process. To realize this concept, we addressed complex chemical, materials science, and engineering problems associated with thermochemical heat engines and the crucial metal-oxide working-materials deployed therein. By project's end, we had demonstrated solar-driven conversion of CO2 to CO, a key energetic synthetic fuel intermediate, at 1.7% efficiency.
This report summarizes the accomplishments of a Laboratory-Directed Research and Development (LDRD) project focused on developing and applying new x-ray spectroscopies to understand and improve electric charge transfer in electrochemical devices. Our approach studies the device materials as they function at elevated temperature and in the presence of sufficient gas to generate meaningful currents through the device. We developed hardware and methods to allow x-ray photoelectron spectroscopy to be applied under these conditions. We then showed that the approach can measure the local electric potentials of the materials, identify the chemical nature of the electrochemical intermediate reaction species and determine the chemical state of the active materials. When performed simultaneous to traditional impedance-based analysis, the approach provides an unprecedented characterization of an operating electrochemical system.
Atmospheric pressure chemical vapor deposition (APCVD) of tin oxide is a very important manufacturing technique used in the production of low-emissivity glass. It is also the primary method used to provide wear-resistant coatings on glass containers. The complexity of these systems, which involve chemical reactions in both the gas phase and on the deposition surface, as well as complex fluid dynamics, makes process optimization and design of new coating reactors a very difficult task. In 2001 the U.S. Dept. of Energy Industrial Technologies Program Glass Industry of the Future Team funded a project to address the need for more accurate data concerning the tin oxide APCVD process. This report presents a case study of on-line APCVD using organometallic precursors, which are the primary reactants used in industrial coating processes. Research staff at Sandia National Laboratories in Livermore, CA, and the PPG Industries Glass Technology Center in Pittsburgh, PA collaborated to produce this work. In this report, we describe a detailed investigation of the factors controlling the growth of tin oxide films. The report begins with a discussion of the basic elements of the deposition chemistry, including gas-phase thermochemistry of tin species and mechanisms of chemical reactions involved in the decomposition of tin precursors. These results provide the basis for experimental investigations in which tin oxide growth rates were measured as a function of all major process variables. The experiments focused on growth from monobutyltintrichloride (MBTC) since this is one of the two primary precursors used industrially. There are almost no reliable growth-rate data available for this precursor. Robust models describing the growth rate as a function of these variables are derived from modeling of these data. Finally, the results are used to conduct computational fluid dynamic simulations of both pilot- and full-scale coating reactors. As a result, general conclusions are reached concerning the factors affecting the growth rate in on-line APCVD reactors. In addition, a substantial body of data was generated that can be used to model many different industrial tin oxide coating processes. These data include the most extensive compilation of thermochemistry for gas-phase tin-containing species as well as kinetic expressions describing tin oxide growth rates over a wide range of temperatures, pressures, and reactant concentrations.