A5015692367- Advanced Thermoelectric Materials and Devices
- Chalcogenide Semiconductor Thin Films
- Thermal properties of materials
- Advanced Semiconductor Detectors and Materials
- Thermal Expansion and Ionic Conductivity
- Rare-earth and actinide compounds
- Advanced ceramic materials synthesis
- Quantum Dots Synthesis And Properties
- Heusler alloys: electronic and magnetic properties
- Electronic and Structural Properties of Oxides
- Microstructure and mechanical properties
- Semiconductor materials and devices
- Ferroelectric and Piezoelectric Materials
- Superconductivity in MgB2 and Alloys
- Surface and Thin Film Phenomena
- Perfectionism, Procrastination, Anxiety Studies
- Adhesion, Friction, and Surface Interactions
- 2D Materials and Applications
- Boron and Carbon Nanomaterials Research
- Composite Material Mechanics
- Semiconductor materials and interfaces
- Machine Learning in Materials Science
- Perovskite Materials and Applications
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
Northwestern University
2019-2024
Jet Propulsion Laboratory
2023
Many monumental breakthroughs in p-type PbTe thermoelectrics are driven by optimizing a Pb0.98Na0.02Te matrix. However, recent works found that x > 0.02 Pb1-xNaxTe further improves the thermoelectric figure of merit, zT, despite being above expected Na solubility limit. We explain origins improved performance from excess doping through computation and experiments on with 0.01 ≤ 0.04. High temperature X-ray diffraction Hall carrier concentration measurements show enhanced at high temperatures...
Typically, conventional structure transitions occur from a low symmetry state to higher upon warming. In this work, an unexpected local breaking in the tetragonal diamondoid compound AgGaTe2 is reported, which, warming, evolves continuously undistorted ground locally distorted while retaining average crystallographic symmetry. This rare phenomenon previously referred as emphanisis. state, caused by weak sd3 orbital hybridization of tetrahedral Ag atoms, causes their displacement off...
Defect chemistry is critical to designing high performance thermoelectric materials. In SnTe, the naturally large density of cation vacancies results in excessive hole doping and frustrates ability control properties. Yet, recent work also associates with suppressed sound velocities low lattice thermal conductivity, underscoring need understand interplay between alloying, vacancies, transport properties SnTe. Here, we report solid solutions SnTe NaSbTe2 NaBiTe2 (NaSnmSbTem+2 NaSnmBiTem+2,...
Semiconductor engineering relies heavily on doping efficiency and dopability. Low may cause low mobility failure to reach target carrier concentrations or even the desired type. Semiconducting thermoelectric materials perform best with degenerate concentrations, meaning high performance in new might not be realized experimentally without a route optimal doping. Doping classic PbTe system has been largely successful but reported efficiencies can vary, raising concerns about reproducibility....
Abstract Grain boundaries critically limit the electronic performance of oxide perovskites. These interfaces lower carrier mobilities polycrystalline materials by several orders magnitude compared to single crystals. Despite extensive effort, improving mobility (to meet crystals) is still a severe challenge. In this work, grain boundary effect eliminated in perovskite strontium titanate (STO) incorporating graphene into microstructure. An effective mass model provides strong evidence that...
Thermoelectric properties are frequently manipulated by introducing point defects into a matrix. However, these often change in unfavorable directions owing to the spontaneous formation of vacancies at high temperatures. Although it is crucial maintain thermoelectric performance over broad temperature range, suppression challenging since their thermodynamically preferred. In this study, using PbTe as model system, demonstrated that dimensionless figure merit, zT ≈ 2.1 723 K, can be achieved...
Abstract Dislocations and the residual strain they produce are instrumental for high thermoelectric figure of merit, zT ≈ 2, in lead chalcogenides. However, these materials tend to be brittle, barring them from practical green energy deep space applications. Nonetheless, bulk thermoelectrics research focuses on increasing without considering mechanical performance. Optimized always involve point defect concentrations doping solid solution alloying. Brittle show limited plasticity...
Cation disordering is commonly found in multinary cubic compounds, but its effect on electronic properties has been neglected because of difficulties determining the ordered structure and defect energetics. An absence rational understanding point defects present led to poor reproducibility uncontrolled conduction type. AgBiSe2 a representative compound that suffers from thermoelectric properties, while origins intrinsic n-type conductivity remain speculative. Here, it demonstrated cation...
Abstract The thermoelectric material ZnSb utilizes elements that are inexpensive, abundant, and viable for mass production. While a high figure of merit zT , is difficult to achieve in Sn‐doped ZnSb, it shown this obstacle primarily due shortcomings reaching enough carrier concentrations. samples prepared different equilibrium phase spaces the ternary Zn‐Sb‐Sn system investigated using boundary mapping, range achievable concentrations found doped samples. sample with highest study, which...
A new understanding of the MgSi–MgSn miscibility gap is reached through phase boundary mapping Mg–Si–Sn ternary diagram.
Stability of any point defect type and the corresponding compound can be visualized within same convex-hull framework. Defect formation enthalpy is determined using intercepts at compositions pure elements involved in formation.
Recent improvements in the efficiency of heat-to-electricity energy conversion lead chalcogenide thermoelectrics involve reducing thermal conductivity by incorporating large amounts internal strain. The extent to which typical processing techniques (such as doping, ball milling, and densification) increase strain dislocation density must be quantified improve materials design. In this study, neutron powder diffraction is leveraged evaluate introduced milling doped undoped powders. Doping...
Designing a high efficiency thermoelectric material for thermal to electric energy conversion means simultaneously optimizing multiple properties of the material. Although it might seem straightforward maximize electrical power and minimize losses, convoluted relationship between these makes optimization complex, requiring more sophisticated algorithm. The Accelerated Insertion Materials (AIM) methodology developed engineer mechanical complex multiphase steel alloys provides framework that...
Fracture mechanics is a fundamental topic to materials science. toughness, in particular, material property of great technological importance for device design. The relatively low fracture toughness many semiconductor materials, including electronic and energy handicaps their use applications involving large external stresses. Here, it shown that quantum-mechanical density functional theory calculations ideal strength, conjunction with an integral stress-displacement method, can be used...
Defect Engineering In article number 2100895, Yeon Sik Jung, Min-Wook Oh, and co-workers demonstrate the underlying defect chemistry on rebounding power factor of an Na Ag co-doped PbTe. Excess doping is proven to be effective Te vacancy scavenger by forming interstitial clusters, which confirmed advanced STEM in situ characterizations.
A decrease in electrical conductivity is measured situ n-type PbTe during dislocation-climb creep deformation at 673 K. Transmission electron microscopy reveals the accumulation of high density immobile dislocations that form stable subgrains which increase with increasing strain from 8 to 20%. At a constant applied stress, we conclude dislocation density, primarily responsible for continuous resistivity strain. With assumption velocity mobile so should dictate total deformation. This effect...