High-temperature superconductors based on complex layered copper oxyfluorides

Chemical aspects of the synthesis of complex layered copper oxyfluorides possessing superconducting properties or serving as structural matrices for the preparation of new superconductors are discussed. Primary attention is given to fluorination of layered cuprates. Different ways of inserting fluorine into complex copper oxides and the corresponding synthetic approaches are surveyed. The influence of the synthesis conditions on the fluorination pathway, which involves either the incorporation of fluorine or partial replacement of oxygen with fluorine, is analysed. The advantages of xenon difluoride over other fluorinating agents are considered. Fluorination of complex copper oxides often leads to structural changes as exemplified by fluorine-containing phases obtained with the use of both XeF₂ and other fluorinating agents. The bibliography includes 104 references.