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Showing 1 to 20 of 23 for “"perovskite oxides"”.
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Spectroscopic perspectives on ultrafast coupling phenomena in perovskite oxides
In this thesis, I study ultrafast dynamics in perovskite oxides using time resolved broadband spectroscopy. I focus on the observation of coherent phonon propagation by time resolved Brillouin scattering: following the excition of metal transducer films with a femtosecond infrared pump pulse, …
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Ferroelectricity Coupled To Octahedral Rotations In Perovskite Oxides From First Principles
… fundamental and technological interest in perovskite oxides, a large class of ceramic materials that exhibit an unprecedented diversity of physical properties. Some perovskites exhibit ferroelectricity, the existence of a field-switchable electric polarization. Other perovskites exhibit …
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Surface structural changes of perovskite oxides during oxygen evolution in alkaline electrolyte
Perovskite oxides such Ba0.5Sr0.5Co0.8Fe0.8O3-6 (BSCF82) are among the most active catalysts for the oxygen evolution reaction (OER) in alkaline solution reported to date. In this work it is shown via high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy that oxides such …
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Ab initio Study of Atomic Dynamics and Thermal Properties of Inorganic Clathrates, Chalcogenides and Perovskite Oxides
… namely inorganic clathrates, chalcogenides and perovskite oxides. Inorganic clathrates are promising candidates for thermoelectric applications due to their low thermal conductivity. In order to test approaches that improve the thermoelectric figure of merit of the inorganic clathrate, …
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Controlling and understanding electro-chemo-mechanical properties of layered cuprate thin films
… mixed ionic-electronic conducting (MIEC) ABO₃ perovskite oxides have been extensively explored as model systems to understand oxygen surface exchange kinetics for solid oxide fuel cell (SOFC) electrodes. Traditionally, transport properties are examined as functions of type and concentration of …
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Understanding and Controlling the Surface Chemistry of Oxides to Enhance Catalytic Activity at Elevated Temperatures
Oxides have been extensively used as high temperature catalysts in electrochemical devices and for gas conversion reactions, including solid oxide fuel cells (SOFC), solid oxide electrolysis cells (SOEC), ethane cracking, CO oxidation, and the oxidative coupling of methane. In hightemperature …
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Activating oxygen chemistry on metal and metal oxides: design principles of electrochemical catalysts
… systems: Pt-metal (Pt-M) alloys for ORR and perovskite oxides for OER. The combination of electrochemical characterizations with transmission electron microscopy (TEM) techniques provides deeper insights on how the basic physical and chemical properties could influence the stability and …
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FIRST ROW TRANSITION METAL OXIDES AS ELECTROCATALYSTS FOR ANION EXCHANGE MEMBRANE FUEL CELLS AND ELECTROLYZERS
… of some non-precious transition metal oxides as candidates for anion exchange membrane fuel cells. These included a series of La-based perovskite oxides and a specific Co-Mn spinel oxide. For characterizing these systems, I employed electrochemical techniques such as cyclic voltammetry …
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Influence of Electronic Structure and Lattice Dynamics on Oxygen Ion Transport in Solid-State Ionic Conductors
… First, the migration energy barrier in perovskite oxides is linked to an electronic energy penalty from local charge screening near the hopping ion. The energy of local electronic states is identified as a fundamental descriptor of the migration barrier. Next, migration entropy and …
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Tuning Strong Correlated Properties in EuTiO3 Thin Films Grown by Pulsed Laser Deposition
Transition metal ABO3 perovskite oxides possess many fascinating and technologically relevant phenomena such as superconductivity, multiferroicity, magnetoresistivity, and photovoltaics. To achieve and enhance these existing functionalities in perovskite oxides, control and tailor of strong …
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Trends in C-H bond dehydrogenation energetics for small molecule conversion
… further developed a rational design approach for perovskite oxides by tuning the surface O 2p-band center to selectively oxidize methanol to formaldehyde. Finally, we extended this descriptor-based approach for oxidative dehydrogenation of propane to propene. Thus, using a combination of kinetic …
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Growth-induced non-stoichiometry in complex oxide systems
Complex perovskite oxides have been studied extensively over the past few decades due to their wide range of functional properties and relative ease of epitaxial synthesis. These two factors have allowed such oxide systems to see a multitude of applications including sensors, memory, thermal …
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Fundamental studies of heterostructured oxide thin film electrocatalysts for oxygen reduction at high temperatures
… clean electrochemical energy technologies. Perovskite oxides are active for surface oxygen exchange at evaluated temperatures and they are used commonly in solid oxide fuel cells (SOFC) or electrolyzers. However, the oxide surface chemistry at high temperatures and near ambient oxygen …
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Activity and Stability Design Principles of Transition Metal Compounds for Decarbonization
… challenge, transition metal compounds, such as oxides and nitrides, have been utilized as low-cost, non-precious catalysts for these sustainable energy technologies. However, the best-known non-precious catalysts to date are still much less active and stable than their precious-metal-based …
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Materials for High Temperature Thin Film Thermocouple Applications
… carbide as well as two families of conducting perovskite oxides viz., cobaltites and manganates (La(1-x)SrxCoO3, M(1-x)Cax MnO3 where, M=La,Y) were investigated for high temperature thin film thermocouple applications as alternate candidate materials. Thin films of the carbides were deposited …
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Combining density functional theory and machine learning for optimization of multicomponent oxide electrocatalysts
Multicomponent metal oxides, such as perovskite oxides, hold promise for use as sustainable alternatives to Ir-, Ru-, and Pt-based electrocatalysts at scale. Perovskites can accommodate a wide variety of elements in their A- and B-sites, enabling tuning of their structural and electronic properties …
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Redox cycles with doped calcium manganites for high-temperature thermochemical energy storage in concentrating solar power
Redox cycles with reducible perovskite oxides of the form ABO$_3$ can provide thermochemical energy storage (TCES) with higher energy density and storage temperatures than molten-salt systems for large-scale energy storage in concentrating solar power (CSP). Perovskites from earth abundant cations …
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Hypersound interaction studied by time-resolved inelastic light and x-ray scattering
… were used to heat nanostructures composed of perovskite oxides on an ultrashort timescale. As a consequence the heated regions of such a nanostructure expand and a high frequency acoustic phonon pulse is generated. To detect such coherent acoustic sound pulses I use ultrafast variants of …
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Ultrafast lattice dynamics in photoexcited nanostructures : femtosecond X-ray diffraction with optimized evaluation schemes
… and lattice dynamics in nanostructures of perovskite oxides. Femtosecond hard X-ray pulses were utilized to probe the evolution of atomic rearrangement directly, which is driven by ultrafast optical excitation of electrons. The physics of complex materials with a large number of degrees of …
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External field effects on electronic and ionic defects in functional oxides: Experiments and simulations
… on electronic and ionic defects in functional oxides is the key to design next generation energy conversion/storage and memory devices. Mechanical strain and high electric fields are known to commonly exist in thin film functional oxides and significantly affect the electronic and ionic defect …
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