Intergrowth compounds

Smicker. D. Van Smaalen. S.V. de Boers. J.L. Haas. C. Harris. K.D.M. Observation of the sliding mode in incommensurate intergrowth compounds Brillouin scattering from the inclusion compound of urea and heptadec-ane. Phys. Rev. Lett. 1995, 74. 734. 

Lefort. R. Etrillard. J. Toudic, B. Guillaume, F. Breczewski, T. Bourges, P. Incommensurate intermodulation of an organic intergrowth compound observed by neutron scattering. Phys. Rev. Lett. 1996. 77.4027. 

The general formulation of these oxides, (ACuOg.x)m(AO)n, reflects for each of them the number m of copper layers which form each perovskite slab, and the number n of AO layers which form each rock salt-type slab (the AO layers which lie at the boundary of the perovskite slabs and rock salt type slabs can only be counted as for 1/2). Thus all these oxides (2-34) can be represented by the symbol [m,n] in which m,n will be integral numbers. In most of these oxides one observes for one compound only one m and n value, corresponding to single intergrowths. 

A higher temperature, Tc l 10K, phase in the Bi-Sr-Ca- Cu-O system has also been reported (78-80). This phase contains three infinite two-dimensional Cu-O layers. However, lead appears to play an important role in stabilizing this compound in phase pure form (75)(79)(80). Single crystals grown by eutectic melt growth techniques have been reported (77) but the phase purity of these crystals with respect to intergrowths containing various numbers of Cu-O planes is a concern. 

Crystal growth of these compounds is complicated by the high volatility of thallium oxides and thallium-containing compounds at elevated temperatures and the toxicity of thallium. Also, the similarity in structures leads to problems controlling phase purity and samples which appear to be single crystals based on their morphology can be shown to be complicated intergrowths by X-ray diffraction studies. 

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