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Origin of Space Charge in Grain Boundaries of Proton-Conducting BaZrO3

Edit E. Helgee (Institutionen för teknisk fysik, Material- och ytteori) ; Anders Lindman (Institutionen för teknisk fysik, Material- och ytteori) ; Göran Wahnström (Institutionen för teknisk fysik, Material- och ytteori)
Fuel Cells (1615-6846). Vol. 13 (2013), 1, p. 19-28.
[Artikel, refereegranskad vetenskaplig]

Segregation energies of oxygen vacancies and protons near three symmetric tilt grain boundaries (GBs) in BaZrO3 are determined using density functional theory. Two of the GBs have the [-110] direction as tilt axis whith a (111) or (112) plane as GB plane, while the third has the [001] direction as tilt axis and a (210) plane as GB plane. Both defects are found to segregate to all three GBs, with vacancy segregation energies of -0.5 and -1.5 eV and proton segregation energies of about -0.8 eV. The effects of the calculated segregation energies on defect concentrations and electrostatic potential in the GB region are investigated using a thermodynamic space charge model. An increased concentration of defects is seen in all GBs, giving electrostatic potential barriers around 0.6 V at 400-900 K. Protons are found to give important contributions to the space charge in all three GBs.

Nyckelord: Conducting Materials, Defect Segregation, Density Functional Calculations, Grain Boundaries, Proton Conductors, Space Charge Theory



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Denna post skapades 2013-01-09. Senast ändrad 2017-06-28.
CPL Pubid: 169889

 

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