Cuprate superconductors crystal structure

Structural and electronic inhomogeneities are characteristic intrinsic properties of the cuprate superconductors related with the unconventional character of these compounds. The YBa2Cu30x (Y123x) compound is a prototype of cuprates with two Cu02 planes been extensively investigated over the 0oxygen concentration [1], The properties and the crystal structure of this material are closely related to x, with... 

The crystal structures (Section 8.2.2) and the phase-relations (Section 8.2.3) of the cuprate superconductors are considerably more complex than for the metallic superconductors. It is not surprising that, while there a common macrotheory, different microtheories are required. 

With the discovery of superconductivity (Tc = 15.5 K) in the Y-Ni-B-C system [6, 80], a new class of quaternary borocarbide superconductors has emerged. Superconductivity has been observed in several rare earth (Lu, Tm, Er and Ho) nickel borocarbides[80], and with transition metals such as Pd and Pt. The superconducting phase having the composition of YNi2B2C, crystallizes [81] in a tetragonal structure with alternating Y-C and Ni2B2 layers. Band structure calculations [82] indicate that these materials, unlike cuprate superconductors, are three-dimensional metals. 

The crystal structures of several high-temperature superconductors (HTSC), particularly in the cuprate family, are describable as built of modules of perovskite together... 

The crystal chemistry of the rare-earth cuprates is discussed in chapter 188 by B. Raveau, C. Michel and H. Hervieu. These authors noted that all of the hiTc superconductors are derived from the perovskite structure. This is done by disconnecting the CuOe octahedra of the perovskite structure along one direction so then an infinite number of CUO2 layers are formed. These layers are responsible for the superconductivity. Raveau et al. note that the rare-earth cations are not directly responsible for the appearance of superconductivity, but by virtue of their large size and trivalent character they help stabilize these layered structures. 

The high-temperature superconductors are a remarkable set of materials that present us with fascinating scientific and technological challenges. The cuprate Ba2YCu307, the first material with a T > 77 K, has a tripled perovskite structure with Cu occupying the small perovskite B site while Ba and Y are ordered on the perovskite A site. Bulk crystals are key to... 

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