- Tytuł:
- Growth Morphology and Atomic Surface Topology by Hartman-Perdok Analysis: Application to ABCO$\text{}_{4}$ and YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-x}$
- Autorzy:
- Woensdregt, C. F.
- Powiązania:
- https://bibliotekanauki.pl/articles/1964232.pdf
- Data publikacji:
- 1997-07
- Wydawca:
- Polska Akademia Nauk. Instytut Fizyki PAN
- Tematy:
-
81.10.Aj
68.35.-p
68.35.Bs - Opis:
- The Hartman-Perdok theory explains the relation between crystal structure and morphology and provides the atomic surface topology of the crystal-melt interface. Hartman-Perdok theory has been applied to CaYAlO$\text{}_{4}$ as model for all other ABCO$\text{}_{4}$ compounds with a K$\text{}_{2}$NiF$\text{}_{4}$ crystal structure. F forms are {002}, {101}, {103}, {110}, {112}, {200}, {211} and {213}. The strongly anisotropic shape caused by the perovskite-like AlO$\text{}_{6}$ layers || {001} is very distinct in all theoretical growth forms. The form with formal charges is planar following {001} with {101} and {110} as lateral forms. Disordering of the boundary ions results in the disappearance of {110}. At lower effective charge on oxygen ions, q$\text{}_{O}$, the ordered forms are still tabular, while {110} and {112} are the only lateral faces. At still lesser negative q$\text{}_{O}$ {112} appears as well. On the disordered models {112} replaces {110}. Crystals show often variations in colour parallel to the {110} interface due to the surface topology of {110}. YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-x}$ has, for x=1, the following F forms: {001}, {101}, {103}, {112} and {114}. The theoretical growth form of this tetragonal phase is tabular following {001} with {101} as lateral form. For x=0 the growth form shows important {101} and minor {103} and {001}. When the boundary ions on (001) are ordered, the outermost layer of {001} contains half of the Cu$\text{}^{+}$ (x=1) or Cu$\text{}^{3+}$ and O$\text{}^{2-}$ (x=0) ions in a c(2×2) quadratic lattice which reduces the {001} growth rate significantly. An (1×2) reconstructed {010} surface can be traced for the orthorhombic polymorph which results into the appearance of {010} on the ordered growth form. Otherwise the presence of {010} on as-grown crystals must be due to external factors.
- Źródło:
-
Acta Physica Polonica A; 1997, 92, 1; 35-46
0587-4246
1898-794X - Pojawia się w:
- Acta Physica Polonica A
- Dostawca treści:
- Biblioteka Nauki
Artykuł