Crystal-chemical structure and electrical conductivity of HTSC – cuprates under conditions of variation of defective composition and exposure to high-energy irradiation (literature review)

Abstract

The review considers the features of the crystal chemical structure of HTSC cuprates and modern ideas about the nature of their electrical conductivity. The analysis of factors affecting the electrical properties of HTSC cuprates is carried out. The reasons for the formation of specific chemical bonds between various ions, leading to the formation of clusters of negative U centers in this compound, as well as experimental facts indicating a close relationship between the crystal chemical structure of metal oxide compounds and their anomalous electrical conductivity are discussed. The anisotropy of their physical properties, in particular, the anisotropy of their electrical conductivity, is associated with the peculiarities of the crystallochemical structure of single-crystal HTSC cuprates. The study of the influence of defects of various nature on the electrical conductivity in various crystallographic directions, under conditions of temperature variation is an important source of experimental data for constructing theoretical models of layered HTSCs. It is shown that, along with the degree of deviation from oxygen stoichiometry, isovalent and non-isovalent substitution, an important method for modifying the electrical properties of cuprates is their irradiation with high-energy electrons. Taking into account modern ideas about the interaction of high-energy radiation with solids, the possible mechanisms of the influence of high-energy radiation on their electrical characteristics are considered. Based on the experimental data presented in the literature, the degree of influence of various processing methods of HTSC cuprates on their electrical conductivity is estimated. Based on the analysis, the conditions for the selection of elements for the synthesis of compounds characterized by a higher temperature of transition to the superconducting state are formulated and issues that have not received their experimental and theoretical solutions are highlighted.