Stabilization of MgAl<sub>2</sub>O<sub>4</sub> spinel surfaces via doping [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description:: pages 138-145 : digital, PDF file
Additional Creators:: Los Alamos National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

Here, the surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. We report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl₂O₄) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y³⁺, Gd³⁺, La³⁺) and one tetravalent dopant (Zr⁴⁺) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.

Report Numbers:

E 1.99:la-ur--16-20588
la-ur--16-20588

Subject(s):

Materials Science

Note:

Published through SciTech Connect.
02/06/2016.
"la-ur--16-20588"
Surface Science 649 C ISSN 0039-6028 AM
Md. M. Hasan; Pratik P. Dholabhai; Ricardo H. R. Castro; Blas P. Uberuaga.

Funding Information:

AC52-06NA25396

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