التفاصيل البيبلوغرافية
| العنوان: |
The {1. |
| المؤلفون: |
Yu-Chuan Wu, Che-Chi Lee, Hong-Yang Lu, McCauley, Daniel E., Chu, Mike S.H. |
| المصدر: |
Journal of the American Ceramic Society; May2006, Vol. 89 Issue 5, p1679-1686, 8p, 5 Black and White Photographs, 5 Diagrams, 1 Graph |
| مصطلحات موضوعية: |
TWINNING (Crystallography), BARIUM compounds, CRYSTAL lattices, SINTERING, X-ray crystallography |
| مستخلص: |
The {1 1} twins frequently observed in pressureless-sintered BaTiO3 ceramics have been analyzed by the X-ray diffractometry, scanning and transmission electron microscopy. Both the single twins and double lamellar twins are growth (or annealing) twins. The twins lying in the {1 1} mirror planes, which is not one of the symmetry elements of the (basic) crystal lattice's but that of the superlattice's, are therefore superlattice twins. The {1 1} twins, particularly the double twins, were found more frequently from samples sintered in an Ar atmosphere of lower oxygen partial pressure (pO2). Further decreasing of pO2 using the Ar-5% H2 mixture has rendered the sintered samples entirely of hexagonal BaTiO3, the 6H-polytype. The formation of such twins is attributed to changing of the corner-sharing TiO6 octahedra to Ti2O9 face-sharing octahedra, which accommodates for local oxygen deficiency in tetragonal BaTiO3. The stacking sequence alters accordingly from c-layer (constituting the 3C-polytype, treating tetragonal pseudo-cubic) to h-layer (as in (chc)1(chc)2 of 6H). [ABSTRACT FROM AUTHOR] |
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