Superconductor perovskite-structure related

The perovskite structure is capable of high anion conductivity when oxide vacancies are introduced, as in, for example, Lai (Sr Co03 (/2 or in the perovskite-related superconductor phases, La2Cu04 and YBa2Cu307. The oxide ion transport number is not unity since such materials are often electronic conductors as well, due to the presence of... 

A Tripled-Perovskite — Relationship to the New High Tc Oxide Superconductor A tripled cell for the perovskite structure is shown in Figure 33. This structure is closely related to that of the new 90 K superconductor in the following way. The structure of the superconductor can be derived from a highly anion-defect, perovs-kite-type structure. The composition can be obtained as follows. 

Chapter 10 covers the exciting field of superconductors, including high-temperature superconductors, many of which have structures related to the perovskite structure. 

All the high Tc superconductors discovered so far, with one exception, contain weakly coupled copper oxide, Cu02, planes. The highest critical temperatures are found for cuprates containing a Group 2 metal (Ca, Ba, Sr) and a heavy metal such as Tl, Bi, or Hg. The structures of all the cuprate superconductors are based on, or related to, the perovskite structure. The one report (in 2000) of a non-cuprate high T superconductor is of surface superconductivity in Na WOs. The structure of NUxWOs is also based on the perovskite structure. 

A common feature of all the new ceramic superconductors is that they are cuprates, that is, they are complex copper oxides. The structure of YBCO is given in Fig. 19.3, which also shows that it is related to the perovskite structure (Fig. 4.17). Synthesis of YBCO is remarkably easy appropriate amounts of dry yttrium oxide (Y203), copper oxide (CuO), and barium carbonate (BaC03) are ground together into a fine, well-mixed... 

The idea of controlling the properties of materials of this type by substitution of ions of different sizes is also shown in a related series [36], that of RENiOj where RE = La, Pr, Nd and Sm. These compounds are not superconductors, but the last three compounds of the series show metal-insulator transitions whose temperature may be controlled by the structural parameters of the solid. These materials crystallize in distorted form of the perovskite structure, the GdFeOj structure, where as shown in Fig. 19, adjacent pairs of NiOj octahedra are bent at the common oxygen atom to improve the oxygen coordination to the rare earth atom. 

The structures of some high-temperature superconductors are also related to that of perovskite. Another mixed oxide lattice is that of spinel, MgAl204 (see Box 12.6). 

The new high-temperature superconductors occur in at least two crystalline forms, both of which are closely related to the perovskite structure. The... 

CUPRATE HIGH-TEMPERATURE SUPERCONDUCTORS 8.6.1 Perovskite-Related Structures and Series... 

STRUCTURES OF THE PEROVSKITE-RELATED YBa2Cu307, YBa2Cu408, AND Y2Ba4Cu7015 SUPERCONDUCTORS... 

The high oxygen diffusivity, even at room temperature, of the 90 K high-temperature superconductor YBayCusOy s (0 < 5 < 1) is one of its remarkable properties. The large concentration of anion vacancies of the perovskite-related structure (i.e. A3B3O9 2) is responsible for the high mobility of this phase. 

---