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c Superconductors
Published in David A. Cardwell, David C. Larbalestier, I. Braginski Aleksander, Handbook of Superconductivity, 2023
Ching-Wu Chu, Liangzi Deng, Bing Lv
All known bulk HTSrs with a Tc above 77 K, the liquid nitrogen boiling point, are perovskite-like cuprates except for the recently reported unit-cell FeSe ultrathin film on a STO substrate [19]. However, the Fe-chalcogenides and their iso-structural Fe-pnictide families have formed a nice platform to help reveal the role of magnetism in HTSy because of the presence of a large amount of the magnetic Fe-element and their relatively simple structure. Magnetism has been proposed by many to be a crucial ingredient in the occurrence of HTSy in the cuprates [10]. This chapter will discuss both systems but focusing mostly on cuprates. The cuprates can be represented by the generic formula AmE2Rn-1CunO2n+m+2 and designated as A-m2(n-1)n, where A, E, and R are cations often with A = Y, rare-earth element, Bi, Tl, or Hg; E = Ba, Sr, or Cu; and R = Ca or a rare-earth element. For some cases, R can be replaced by a (RO)-layer or by a more complex oxide slab. When A is absent, they are designated as 02(n-1)n. These HTSg cuprates possess a layered structure (Figure D4.2) [20] consisting of n CuO2-layers per unit formula separated by n-1 R-layers, denoted by {(CuO2)[R(CuO2)]n-1}, known as the active block (AB), and mAO-layers sandwiched between two EO-layers, denoted by [(EO)(AO)m(EO)], known as the charge reservoir block (CRB).
The structure of of cuprate superconductors
Published in J. R. Waldram, Superconductivity of Metals and Cuprates, 2017
Cuprates are usually first prepared by solid-state reaction of the powdered oxides, carbonates or nitrates of the metals involved, with the cations in the required ratios. The ratios must be accurately controlled, and the reagents must be finely ground and very thoroughly mixed, because the multicomponent phase diagrams usually show competing compounds at nearby compositions. Particle sizes of a few μm are required, and, in the case of YBCO, the powder is calcined at 900–950 °C. Repeated grinding and calcining is usually necessary.
c oxide superconductors
Published in D R Vij, Handbook of Electroluminescent Materials, 2004
D D Shivagan, B M Todkar, S H Pawar
The discovery of high-temperature superconductivity in La-based cuprate by Bednorz and Muller in 1986 [1] stimulated unprecedented excitement and led to the discovery of different families of cuprates, which remain superconducting at appreciable temperature. Some of the important ones were Y(RE)-123, Bi-2122/2223, Tl-2122/2223 and Y-124, Hg-1223 and MgB2. Though superconductivity is a transport phenomenon, there are several good reasons for the investigations of luminescence in these materials. One of them is that many of these high-Tc materials belong to a class of materials of oxygen-dominated lattices. The luminescence of oxygen-dominated lattices has been observed for many years in naturally occurring phosphates, silicates, carbonates and other materials. Their tremendous commercial importance has had a strong influence on the nature of the work done on oxygen-dominated materials. Another most important reason for studying luminescence is the sensitivity of this technique to defect properties of the materials like defect concentration, disorder, substitution or contamination of a special system with other phases. It is particularly this latter reason which makes luminescence studies attractive for the research work in the field of high-temperature cuprate materials. The data available on luminescence aspects, however, remain relatively scant. This is due to the fact that these materials are uniformly black and of course opaque to visible radiation. Luminescence observed is thus strictly confined to the surface regions and the comparatively less intense as found in various other systems such as sulphide and sulphate phosphors doped with rare earth impurities [2–14]. Nevertheless, the new materials have been studied for a variety of luminescence phenomena like photo-, thermo-, electro- and cathodo-luminescence. This chapter deals with the different types of luminescence found in these novel systems and in particular the electroluminescence (EL) of (123) high-Tc oxide superconductors.
Synthesis of nanostructured cupric oxide for visible light assisted degradation of organic wastewater pollutants
Published in Cogent Engineering, 2021
David Dodoo-Arhin, Etchu E. Mbu, Seteno K. Ntwampe, Edward N. Malenga, Elvis Fosso-Kankeu, Benjamin Agyei-Tuffour, Emmanuel Nyankson, Abu Yaya, Henry Agbe
When investigating complex cuprates, copper oxides can be used as reference materials, since most cuprates have shown high-Tc superconductivity due to a Jahn-Teller distortion associated with the structural characteristics of their divalent copper monoxide structure. This phenomenon tends to introduce strong electron–phonon interactions for the impartation of the required superconductivity and photocatalytic dye degradation process (Kamimura et al., 2005). To fully understand the origin and mechanism of this phenomenon, numerous studies have ensued on simple and complex copper oxides (Elwell et al., 2017). Cupric oxide (CuO) is unique amongst many of the oxides within the 3d transition series. This is largely because of its unique monoclinic structured planar square coordination. The copper bonds with oxygen in a four coplanar arrangement within a distorted tetrahedral environment, and at the same time being coordinated by four other copper atoms. Two sets of chains directed along the [110] and staggered along the [001] planes then form a three dimensional crystal structure of the CuO (Åsbrink & Norrby, 1970; Tunell et al., 1935). Overall, some research interest on Tenorite (CuO), a p-type semiconductor, is based on its ease of synthesis, benignity to organisms and ease of engineering to give it a variety of morphologies at the nanoscale level which can be enhanced for high catalytic activity by narrowing the energy band-gap within 1.2–1.8 eV (Bhattacharjeea & Ahmaruzzaman, 2016). in view of these, CuO has found applications in catalysis, solar energy systems, super-capacitors, and as electrode material for lithium-ion batteries (Shaikh et al., 2011).