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Crystal Chemistry of High-Tc Superconducting Copper Oxides by Professor Dr. Bernard Raveau, Professor Dr. Claude Michel,

By Professor Dr. Bernard Raveau, Professor Dr. Claude Michel, Professor Dr. Maryvonne Hervieu, Professor Dr. Daniel Groult (auth.)

The contemporary discovery of high-temperature superconductivity in copper­ dependent oxides is an occasion of significant significance not just with recognize to the actual phenomenon itself but in addition since it certainly indicates that good kingdom chemistry, and particularly the crystal chemistry of oxides, has a very important position within the synthesis and figuring out of latest fabrics for destiny appli­ cations. the varied papers released within the box of excessive Tc supercon­ ductors within the final 5 years display that the nice complexity of those fabrics necessitates an in depth collaboration among physicists and reliable nation chemists. This e-book is predicated to a wide volume on our event of the crystal chemistry of copper oxides, which we now have been learning within the laboratory for greater than twelve years, however it additionally summarizes the most effects which were got for those compounds within the final 5 years with regards to their dazzling superconducting homes. we've got taken with the struc­ ture, chemical bonding and nonstoichiometry of those fabrics, taking into account that redox reactions are the main to the optimization in their supercon­ ducting houses, because of the significance of the combined valence of copper and its Jahn-Teller impression. now we have additionally drawn on reports of prolonged defects through high-resolution electron microscopy and on their production via ir­ radiation effects.

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These small displacements can be assumed to be the consequence of an ordering of the oxygen vacancies, whose contribution to the intensities is too small to be detected by Xray powder diffraction. The stabilization, in this system, of Cu(III) just by heating the oxides in air is worth noting, but the most important characteristic of this system concerns the existence of a Cu(III) composition range (0 < x < I) that lies between two Cu(II) regions (x=O and x~ 1), for :;tructures closely related to each other.

Examples of oriented domains. (a) Small [001] areas can be observed in [100] oriented crystals. (b) Orthogonal arrangement of two c-axes: Note that the boundaries are straight and sharp. (c) Another orthogonal arrangement of c-axes: Note that the orientations are observed without any boundary between the domains. (d) Examples of striped domains A, w2 = 35 A, w3 = 230 A, w4 = 100 Aand Ws = 35 A It should be noted that in the arrowed areas (domains 1 and 5) a misorientation is observed. 38, but these are not the only ones and many other types of junctions between 123 domains can be proposed.

Projection of the structure of Y2 CUa 0 6 onto (00 I). The z values are indicated and the number of each atom is noted in parentheses tures of Y20g, BaCOg or Ba02 and CuO at 900°C in air, followed by sintering at 1000°C for some hours in an oxygen flow and finally cooling slowly or annealing under oxygen at a low temperature (400 0 - 5000 C). 43,44]. The X-ray diffraction study of "single crystals" did not allow the correct structure to be determined owing to the systematic twinning of the crystals.

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