Metallic, oxygen-deficient compounds in the Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form. Samples withx=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, the samples show a linear decrease in resistivity, then an approximately logarithmic increase, interpreted as a beginning of localization. Finally an abrupt decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative superconductivity. The highest onset temperature is observed in the 30 K range. It is markedly reduced by high current densities. Thus, it results partially from the percolative nature, bute possibly also from 2D superconducting fluctuations of double perovskite layers of one of the phases present.

Possible high Tc superconductivity in the Ba-La-Cu-O system

Structural and Magnetic Studies of Ordered Oxygen-Deficient PerovskitesLnBaCo2O5+δ, Closely Related to the “112” Structure

The review dwells on the problems of high-temperature superconductivity. Ideas encouraging the search for high-temperature superconductivity are elucidated. The way from cubical alloys, containing niobium, to laminated copper-containing oxides with the perovskite-type structure is shown. Properties of new laminated oxide superconductors are described.

Perovskite‐Type Oxides—the New Approach to High—Tc Superconductivity

Introduction, H.J.M. Bouwmeester and P.J. Gellings Principles of Electrochemistry, H. Gerischer Solid State Background, I. Abrahams and P.G. Bruce Interface Electrical Phenomena in Ionic Solids, J. Nowotny Defect Chemistry in Solid State Electrochemistry, J. Schoonman Survey of Types of Solid Electrolytes, T. Kudo Electrochemistry of Mixed Ionic-Electronic Conductors, I. Riess Electrodics, I. Riess and J. Schoonman Principles of Main Experimental Methods, W. Weppner Electrochemical Sensors, P. Fabry and E. Siebert Solid State Batteries, C. Julien Solid Oxide Fuel Cells, A. Hammou and J. Guindet Electrocatalysis and Electrochemical Reactors, C.G. Vayenas and S. Bebelis Dense Ceramic Membranes for Oxygen Separation, H.J.M. Bouwmeester and A.J. Burggraaf Corrosion Studies, J.H.W. de Wit and T. Fransen Electrochromism and Electrochromic Devices, G.C. Granqvist Index

The CRC handbook of solid state electrochemistry

Publisher Summary This chapter discusses the structure and reactivity of perovskite-type oxides. Perovskite-type oxides have the general formula ABO 3 (A, cation of larger size) and are structurally similar to CaTiO 3 , the mineral that gave its name to that group of compounds. These materials are first studied because of their important physical properties such as ferro-, piezo-, and pyroelectricity, magnetism and electrooptic effects. The most numerous and most interesting compounds with the perovskite structure are oxides. Some hydrides, carbides, halides, and nitrides also crystallize with this structure. The chapter reviews only the study of oxides and their behavior in the gas solid interface and in heterogeneous catalysis. An important characteristic of perovskites, mentioned in the chapter, is their susceptibility of partial substitution in both A and B positions. This provides a wealth of isomorphic compounds that can easily be synthesized. Given the extensive range of possibilities in the tailoring of their chemical and physical properties, there is no doubt that new reactions can be studied, where these oxides can participate as catalytic agents.

L. Er-Rakho

Papers

Intercroissance de feuillets “perovskites lacunaires” et de feuillets type chlorure de sodium: Les oxydes La2−xA1+xCu2O6−x2 (A = Ca, Sr)

YBaCuFeO5+δ: a novel oxygen-deficient Perovskite with a layer structure

A series of oxygen-defect perovskites containing CuII and CuIII: The oxides La3−xLnxBa3 [CuII5−2y CuIII1+2y] O14+y

The oxygen defect perovskite BaLa4Cu5O13.4, a metallic conductor

La8−xSrxCu8O20: An oxygen-deficient perovskite built of CuO6, CuO5, and CuO4 polyhedra