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HRTEM; SAED; layer compounds; copper vanadium telluride; copper niobium telluride; copper tantalum telluride; modulated superstructure
Abstract:
The copper intercalation compounds Cu0.87VTe2, CuNbTe2 and Cu0.89TaTe2
which were synthesised from the binary tellurides via topotactic low
temperature intercalation reactions, were investigated by HRTEM and
SAED. All the samples show microdomains with different types of order.
Apart from the average structure which was revealed from Rietveld
refinements earlier, also domains of commensurate superstructures with
a fourfold b-axis and incommensurate modulations with q approximate to
(0 1/4.2 0) are found. These domains show wave-like contrasts in the
HRTEM micrographs. The "waves" have different propagation vectors,
which can be related to the position of satellite reflections in SAED.
For CuNbTe2, a large number of structure models was tested, which were
based on the single crystal structure Of CU0.70NbTe2 (P2(1)/m (no. 11),
a = 6.6872(9), b = 3.7018(5) and c = 7.324(1) angstrom, beta =
107.270(2)degrees). Finally, a structure model with a simple distortion
is presented, which accounts for the superstructures seen in SAED, the
wave-like contrast and the different propagation directions in the
HRTEM micrographs. (c) 2006 Elsevier Masson SAS. All rights reserved.
