HRTEM and SAED investigations of Cu(x)MTe2 (M = V, Nb, Ta)

• Published in: Solid state sciences 2006-10, Vol.8 (10), p.1187-1192
• Main Authors: Sorgel, Timo, Kienle, Lorenz, Jansen, Martin
• Format: Article
• Language: English
• ISSN: 1293-2558
• DOI: 10.1016/j.solidstatesciences.2006.04.015

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 approx (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 Cu0.07NbTe2 (P2(1)/m (no. 11), a = 6.6872(9), b = 3.7018(5) and c = 7.324(1) A(ngstrom), beta =107.270(2) deg ). 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.