Transforming an Ionic Conductor into an Electronic Conductor via Crystallization: In Situ Evolution of Transference Numbers and Structure in (La,Sr)(Ga,Fe)O3‐x Perovskite Thin Films

Advanced Functional Materials, vol. 34

Abstract

Abstract Mixed‐conducting perovskites are workhorse electrochemically active materials, but typical high‐temperature processing compromises their catalytic activity and chemo‐mechanical integrity. Low‐temperature pulsed laser deposition of amorphous films plus mild thermal annealing is an emerging route to form homogeneous mixed conductors with exceptional catalytic activity, but little is known about the evolution of the oxide‐ion transport and transference numbers during crystallization. Here the coupled evolution of ionic and electronic transport behavior and structure in room‐temperature‐grown amorphous (La,Sr)(Ga,Fe)O3‐x films as they crystallize is explored. In situ ac‐impedance spectroscopy with and without blocking electrodes, simultaneous capturingsynchrotron‐grazing‐incidence X‐ray diffraction, dc polarization, transmission electron microscopy, and molecular dynamics simulations are combined to evaluate isothermal and non‐isothermal crystallization effects and the role of grain boundaries on transference numbers. Ionic conductivity increases by ≈2 orders of magnitude during crystallization, with even larger increases in electronic conductivity. Consequently, as crystallinity increases, LSGF transitions from a predominantly ionic conductor to a predominantly electronic conductor. The roles of evolving lattice structural order, microstructure, and defect chemistry are examined. Grain boundaries appear relatively nonblocking electronically but significantly blocking ionically. The results demonstrate that ionic transference numbers can be tailored over a wide range by tuning crystallinity and microstructure without having to change the cation composition.

Authors 7

1. Haley B. Buckner

   University of Illinois Urbana-Champaign

   Affiliation as printed

   Department of Materials Science & Engineering University of Illinois at Urbana‐Champaign 1304 W. Green St. Urbana IL 61801 USA

   Materials Research Laboratory University of Illinois at Urbana‐Champaign 104 S. Goodwin Ave. Urbana IL 61801 USA

   Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL, 61801 USA

   Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 S. Goodwin Ave., Urbana, IL, 61801 USA

2. Joshua Simpson‐Gomez

   University of Illinois Urbana-Champaign

   Affiliation as printed

   Department of Materials Science & Engineering University of Illinois at Urbana‐Champaign 1304 W. Green St. Urbana IL 61801 USA

   Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL, 61801 USA

3. Alexander Bonkowski Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

4. Kathrin Rübartsch Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

5. Hua Zhou

   Argonne National Laboratory · Advanced Photon Source

   Affiliation as printed

   Advanced Photon Source Argonne National Laboratory 9700 S. Cass Avenue Lemont IL 60439 USA

   Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL, 60439 USA

6. Roger A. De Souza Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

7. Nicola H. Perry corresponding

   University of Illinois Urbana-Champaign

   Affiliation as printed

   Department of Materials Science & Engineering University of Illinois at Urbana‐Champaign 1304 W. Green St. Urbana IL 61801 USA

   Materials Research Laboratory University of Illinois at Urbana‐Champaign 104 S. Goodwin Ave. Urbana IL 61801 USA

   Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL, 61801 USA

   Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 S. Goodwin Ave., Urbana, IL, 61801 USA