X-ray nanodiffraction studies of ionically controlled nanoscale phase separation in cobaltites

Journal Article · 04 August 2019 · Physical Review Materials

DOI: https://doi.org/10.1103/PhysRevMaterials.3.082001 · OSTI ID:1562285

Rippy, Geoffery ^[1]; Trinh, Lacey ^[1]; Kane, Alexander M. ^[1]; Ionin, Aleksey L. ^[1]; Lee, Michael S. ^[1]; Chopdekar, Rajesh V. ^[1]; Christiansen-Salameh, Joyce M. ^[1]; Gilbert, Dustin A. ^[2]; Grutter, Alenxander J. ^[3]; Murray, Peyton D. ^[4]; Holt, Martin V. ^[5]; Cai, Zhonghou ^[6]; Liu, Kai ^[7]; Takamura, Yayoi ^[1]; Kukreja, Roopali ^[1]

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1. Univ. of California Davis, Davis, CA (United States). Dept. of Materials Science and Engineering
2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering
3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). NIST Center for Neutron Research
4. Univ. of California Davis, Davis, CA (United States). Dept. of Physics
5. Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials
6. Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Proton Source
7. Univ. of California Davis, Davis, CA (United States). Dept. of Physics; Georgetown Univ., Washington, D.C. (United States). Dept. of Physics

Complex oxide heterostructures provide access to emergent functional and structural phases that are not present in the bulk constituent materials. In this Rapid Communication, we focus on $$La_{0.67}Sr_{0.33}CoO_3$$ (LSCO)/Gd heterostructures due to the high oxygen ion conductivity, as well as the coupled magnetic and electronic properties of LSCO, which are strongly dependent on the oxygen stoichiometry. This combination of properties enables the ionic control of the functional properties of LSCO thin films through the presence of oxygen getter layers such as Gd.We utilize x-ray nanodiffraction to directly image the nanoscale morphology of LSCO thin films as they are progressively transformed from the equilibrium perovskite phase to the metastable brownmillerite (BM) phase with increasing Gd thickness. Our studies show the coexistence of perovskite and BM phases with a critical oxygen vacancy concentration threshold which leads to the formation of extended BM filaments. In addition to lateral phase separation, we observed phase separation within the film thickness possibly due to pinning of the perovskite and BM phases by the substrate/LSCO and LSCO/Gd interface, respectively. Our studies provide a nanoscale survey of the phase separation in the cobaltites and shed light on the formation of the metastable BM phase.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); University of California–Davis, Davis, CA (United States); National Science Foundation (NSF)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1562285
• Alternate ID(s): OSTI ID: 1547991; OSTI ID: 1573808; OSTI ID: 1581604
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 8 Vol. 3; ISSN PRMHAR; ISSN 2475-9953
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English