Density-functional study of the La₂Zr₂O₇ low-index surfaces

Journal Article · 26 April 2018 · Surface Science

DOI: https://doi.org/10.1016/j.susc.2018.04.010 · OSTI ID:1582394

Mantz, Yves A. ^[1]; Duan, Yuhua  ^[2]

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1. National Energy Technology Lab. (NETL), Morgantown, WV (United States)
2. National Energy Technology Lab. (NETL), Pittsburgh, PA (United States)

We report that in order to explain the ability of lanthanum zirconate (La₂Zr₂O₇, LZ) and various doped forms of LZ to function as catalysts, an understanding of LZ surface structures is needed. Accordingly, certain LZ surfaces that are expected to be prevalent in prepared samples of LZ, namely, the low-index (001), (011), and (111) surfaces, are examined at the level of density-functional theory. All possible surface terminations of these surfaces formed by cleaving a perfect LZ crystal, termed ideal surface terminations, are considered, as well as several defective surface terminations of a given surface. Surface energies and surface free energies are computed, and surface phase diagrams (SPDs) of the (001), (011), and (111) surfaces are obtained. From these SPDs, the thermodynamically preferred surface termination of the (001), (011), or (111) surface is concluded to be nonideal over a large range of temperature and oxygen gas partial pressure conditions. This finding is unchanged if the SPDs are determined more accurately by taking into account certain vibrational contributions obtained from computed phonon dispersions. Additionally, a way to use results to characterize the surfaces of synthesized LZ crystallites is discussed, but the shapes or dimensions of the crystallites first need to be obtained.

• Research Organization: National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• OSTI ID: 1582394
• Report Number(s): NETL-PUB-22200
• Journal Information: Surface Science, Vol. 689, Issue C; ISSN 0039-6028
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English