Alexandra Zevalkink
California Institute of Technology
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Featured researches published by Alexandra Zevalkink.
Energy and Environmental Science | 2011
Alexandra Zevalkink; Eric S. Toberer; Wolfgang G. Zeier; Espen Flage-Larsen; G. Jeffrey Snyder
Thermoelectric materials directly convert thermal energy into electrical energy, offering a promising solid-state solution for waste heat recovery. For thermoelectric devices to make a significant impact on energy and the environment the major impediments are the efficiency, availability and toxicity of current thermoelectric materials. Typically, efficient thermoelectric materials contain heavy elements such as lead and tellurium that are toxic and not earth abundant. Many materials with unusual structures containing abundant and benign elements are known, but remain unexplored for thermoelectric applications. In this paper we demonstrate, with the discovery of high thermoelectric efficiency in Ca3AlSb3, the use of elementary solid-state chemistry and physics to guide the search and optimization of such materials.
Journal of the American Chemical Society | 2017
Marvin A. Kraft; Sean P. Culver; Mario Calderon; Felix Böcher; Thorben Krauskopf; Anatoliy Senyshyn; Christian Dietrich; Alexandra Zevalkink; Jürgen Janek; Wolfgang G. Zeier
In the search for novel solid electrolytes for solid-state batteries, thiophosphate ionic conductors have been in recent focus owing to their high ionic conductivities, which are believed to stem from a softer, more polarizable anion framework. Inspired by the oft-cited connection between a soft anion lattice and ionic transport, this work aims to provide evidence on how changing the polarizability of the anion sublattice in one structure affects ionic transport. Here, we systematically alter the anion framework polarizability of the superionic argyrodites Li6PS5X by controlling the fractional occupancy of the halide anions (X = Cl, Br, I). Ultrasonic speed of sound measurements are used to quantify the variation in the lattice stiffness and Debye frequencies. In combination with electrochemical impedance spectroscopy and neutron diffraction, these results show that the lattice softness has a striking influence on the ionic transport: the softer bonds lower the activation barrier and simultaneously decrease the prefactor of the moving ion. Due to the contradicting influence of these parameters on ionic conductivity, we find that it is necessary to tailor the lattice stiffness of materials in order to obtain an optimum ionic conductivity.
Inorganic chemistry frontiers | 2018
Wanyue Peng; Sevan Chanakian; Alexandra Zevalkink
Compounds that crystallize in the layered CaAl2Si2 structural pattern have rapidly emerged as an exciting class of thermoelectric materials with attractive n- and p-type properties. More than 100 AM2X2 compounds that form this structure type – characterized by anionic M2X2 slabs sandwiched between layers of octahedrally coordinated A cations – provide numerous potential paths to chemically tune every aspect of thermoelectric transport. This review highlights the chemical diversity of this structure type, discusses the rules governing its formation and stability relative to competing AM2X2 structures (e.g., ThCr2Si2 and BaCu2S2), and attempts to bring some of the most recently discovered compounds into the spotlight. The discussion of thermoelectric transport properties in AM2X2 compounds focuses primarily on the intrinsic parameters that determine the potential for a high figure of merit: the band gap, effective mass, degeneracy, carrier relaxation time, and lattice thermal conductivity. We also discuss routes that have been used to successfully control the carrier concentration, including controlling the cation vacancy concentration, doping, and isoelectronic alloying (approaches that are highly interdependent). Finally, we discuss recent progress made towards n-type doping in this system, highlight opportunities for further improvements, as well as open questions that still remain.
Advanced Functional Materials | 2010
Eric S. Toberer; Alexandra Zevalkink; Nicole Crisosto; G. Jeffrey Snyder
Journal of Materials Chemistry | 2014
Sabah Bux; Alexandra Zevalkink; Oliver Janka; David Uhl; Susan M. Kauzlarich; Jeff Snyder; Jean-Pierre Fleurial
Journal of Materials Chemistry | 2014
Saneyuki Ohno; Alexandra Zevalkink; Yoshiki Takagiwa; Sabah Bux; G. Jeffrey Snyder
Chemistry of Materials | 2014
Nasrin Kazem; Weiwei Xie; Saneyuki Ohno; Alexandra Zevalkink; Gordon J. Miller; G. Jeffrey Snyder; Susan M. Kauzlarich
Chemistry of Materials | 2015
Nasrin Kazem; Antonio Hurtado; Fan Sui; Saneyuki Ohno; Alexandra Zevalkink; Jeff Snyder; Susan M. Kauzlarich
Joule | 2018
Dean Cheikh; Brea E. Hogan; Trinh Vo; Paul von Allmen; Kathleen Lee; David M. Smiadak; Alexandra Zevalkink; Bruce Dunn; Jean-Pierre Fleurial; Sabah Bux
Joule | 2018
Wanyue Peng; Guido Petretto; Gian-Marco Rignanese; Geoffroy Hautier; Alexandra Zevalkink