Superconductivity up to 64 K in the copper oxyfluorides Sr2−xAxCuO2F2+δ(A = Ca, Ba) prepared using NH4F as a fluorinating reagent

Superconducting Sr2−xAxCuO2F2+δ(A=Ca, Ba): Synthetic Pathways and Associated Structural Rearrangements

“…Examination of alternative synthetic strategies revealed that these new superconductors could also be obtained by simple solid-state reactions between Sr \V A V CuO and fluorinating agents such as NH F and MF , where M is a transition metal (e.g., CuF , ZnF , NiF , AgF (12,15). In this way, the toxicity and obvious handling problems associated with elemental F gas can be easily avoided.…”

Ab initioperiodic approach to electronic structure and magnetic exchange inA2CuO2X2Moreira1, Dovesi2 2003Phys. Rev. B10010View full textAdd to dashboardCite

“…Moreover, the closely related compound Sr 1.4 Ba 0.6 CuO 2 F 2ϩ␦ is a p-type superconductor with T c ϭ64 K, one of the highest known critical temperatures for a monolayered HTSC with T structure. 21 In clear contrast, Sr 2 CuO 2 Cl 2 also crystallizes with the T structure but has not been found to become superconductor, probably due to the large stability of the stoichiometric compound which is very difficult to dope, especially by cation substitution. 8 Ca 2 CuO 2 F 2ϩ␦ and the stoichiometric phase of Sr 2 CuO 2 F 2 crystallize in the TЈ structure; the former seems not to be superconducting for the available anion doping concentrations.…”

“…Moreover, if a linear relation between T c max and the J/t relation is considered, and if the value of t is supposed to be close to 0.57 eV, the value derived for Ca 2 CuO 2 Cl 2 using the same cluster approach, the expected value of T c max is in the ͓45,55͔ K range which is close to the highest known critical temperature for a monolayered HTSC with La 2 CuO 4 structure. 21 In our opinion, the investigation of alternative doping processes of this material is an appealing research field since it should provide a new series of HTSC's and important tests of the present models of superconductivity.…”

“…10,11͒, and also in the closely related compound Sr 1.4 Ba 0.6 CuO 2 F 2ϩ␦ , which shows one of the highest known critical temperatures for a monolayered HTSC with La 2 CuO 4 structure. 21 However, the closely related compounds Sr 2 CuO 2 Cl 2 , Ca 2 CuO 2 F 2ϩ␦ seem not to be superconducting for the available doping concentrations. 8,17,18 Since experimental and theoretical investigations of their properties seem to indicate that there are no substantial differences between them or with respect to other superconducting cuprates, it is important to study the electronic structure of the full set of compounds in detail in order to carefully evidentiate similarities and differences, and this will be the object of the present paper.…”

Synthesis of Bi₂(O,F)S₂ superconductors by NaF treatment

“…7) Bi 2 (O,F)S 2 is obtained by topotactic fluorination of Bi 2 OS 2 using XeF 2 , 8) although it is explosive, corrosive and toxic. Various fluorination sources have been reported to synthesize various oxyfluorides, such as F 2 gas, 9) NH 4 F, 10) MF 2 or MF 3 (M = Cu, Zn, alkali-earth or lanthanide metal) 6),11),12) and polytetrafluoroethylene. 13) In this study, we investigate the fluorination of Bi 2 OS 2 using NaF.…”