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Combined X‐ray diffraction and solid‐state 19 F magic angle spinning NMR analysis of lattice defects in nanocrystalline CaF 2
Author(s) -
Abdellatief Mahmoud,
Abele Matthias,
Leoni Matteo,
Scardi Paolo
Publication year - 2013
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889813016944
Subject(s) - nanocrystalline material , materials science , magic angle spinning , crystallography , diffraction , powder diffraction , homogeneity (statistics) , x ray crystallography , spinning , lattice constant , analytical chemistry (journal) , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , chemistry , nanotechnology , optics , composite material , physics , statistics , mathematics , chromatography
Nanocrystalline CaF 2 powder specimens were produced both by co‐precipitation of CaCl 2 and NH 4 F and by ball milling of a coarse powder. The specimen homogeneity and a detailed picture of the lattice defects can be assessed by the simultaneous analysis of the powder diffraction pattern and of the solid‐state 19 F magic angle spinning NMR T 1 relaxometry data. While diffraction line profiles provide information on domain size distribution and the content of dislocations, T 1 relaxometry is more sensitive to inhomogeneity of the powder (large defect‐free grains versus defective small ones). After extensive milling it is possible to obtain fluorite domains of comparable size to the chemically synthesized CaF 2 ( circa 10–12 nm), but with a marked difference in the lattice defect types and content. It is then proved that surface defects (related to domain size), line defects (dislocations) and point (Frenkel) defects have a quite different effect on the powder pattern as well as on the T 1 spin‐lattice relaxation time.