Cluster intergrowth of perovskite and defect sodium chloride type structures in the K-Nb-O system: The structure of @KNb sub 4 O sub 6
- Stockholm Univ. (Sweden)
A new reduced potassium niobate ({approximately}KNb{sub 4}O{sub 6}) of intergrowth type structure containing condensed Nb{sub 6}O{sub 12} clusters has been found. The structure has been determined from HREM images. The atomic positions have been refined with the Rietveld technique using X-ray powder diffraction data. The space group of KNb{sub 4}O{sub 6} is P4/mmm; Z = 1, and its unit cell parameters are a = 4.1393(1) and c = 8.2537(2). {approximately}KNb{sub 4}O{sub 6} consists of alternating slabs of KNbO{sub 3} (perovskite) and NbO (ordered deficient NaCl-type) both being a single unit thick. The structure is closely related to that of A{sub 2}Nb{sub 5}O{sub 9} (A = Ba, Sr). Both phases can be considered as members (n = 1 and 2 respectively) of a homologous series A{sub n}Nb{sub 3+n}O{sub 3+3n}. Electron microscopy studies show the presence of defects, both as extra perovskite layers and missing NbO slabs, together with areas of more disordered intergrowth. The profile refinement and microanalysis of individual crystal fragments both indicate the structure to be niobium deficient according to the formula K{sub 1+x/2}Nb{sub 4{minus}x}O{sub 6}.
- OSTI ID:
- 5691160
- Journal Information:
- Journal of Solid State Chemistry; (USA), Journal Name: Journal of Solid State Chemistry; (USA) Vol. 90:2; ISSN 0022-4596; ISSN JSSCB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
INFORMATION
MEASURING METHODS
MICROSCOPY
MINERALS
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITE
PEROVSKITES
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
REFRACTORY METAL COMPOUNDS
SCATTERING
SPACE GROUPS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION