High-temperature superconductors based on complex layered copper oxyfluorides

The chemical aspects of the synthesis of complex layered copper oxyfluorides possessing superconducting properties or serving as structural matrices for the preparation of new superconductiors are discussed. Primary attention is devoted to fluorination of layered cuprates and the effect of synthesis conditions on the fluorination pattern, which is either fluorine insertion or substitution of fluorine for some of the oxygen. Various ways of controduction of fluorine into complex oxides and the corresponding synthesis approach are considered. Advantages of xenon difluoride over other fluorinating agents are noted. It is shown that fluorination of complex copper oxides often leads to structural changes which are illustrated in relation to fluorinae-containing phases obtained using XeF2 and other fluorinating reagents.