PbY_1 xCa_xBa₂Cu₃O₇F₂: synthesis, structure and superconductivity

Abstract

A new phase, PbYBa2Cu3O7F2, has been synthesized and characterized. The material is obtained from the fluorination of PbYBa2Cu3O7 and retains structural relationships to this phase and PbYBaSrCu3O7+δ. The unit cell is tetragonal: space group I4mm, a = 3.8666(2) Å, c = 29.532(2) Å. Fluorine inserts into the structure in the vicinity of the linear Cu2 species present in PbYBa2Cu3O7, and additional structural rearrangement converts the coordination around Cu2 to square pyramidal (four equatorial F and one apical O). Although oxidation of PbYBa2Cu3O7+δ via oxygen incorporation has previously been reported to result in almost complete cation disorder between the Pb and Cu2 cations, low temperature fluorination occurs with no loss of order. PbYBa2Cu3O7F2 is superconducting ( K), and Ca-doping on the Y sites results in an increase in Tc to 50 K and an enhanced superconducting volume fraction.

Crystal Chemistry and Selected Physical Properties of Inorganic Fluorides and Oxide-Fluorides

“…Fluorine mobility appears in HT-Pb 2 ZnF 6 , while superconductivity is well established in PbY 1– x Ca x Ba 2 Cu 3 O 7 F 2 and was the subject of intense research (Figure c), or Sr 2 CuO 2 F 2+δ . It is also theoretically predicted that [AgF 4/2 ] layers in Ag 2+ fluorides, AgF 2 , A 2 AgF 4 (A = K, Rb, Cs), could play the role of CuO 2 layers in oxide superconductors .…”

Review on Synthesis, Characterization, and Electrochemical Properties of Fluorinated Nickel‐Cobalt‐Manganese Cathode Active Materials for Lithium‐Ion Batteries

“…The (non)‐fluorinated CAMs (LiM x O y and LiM x O y F z ; M=Ni, Co, and/or Mn) were compared with comparable systems like (non)‐fluorinated metal oxide compounds, i. e. (non)‐fluorinated super con ductors (M x O y and M x O y F z ) . For example, YBa 2 Cu 3 O x F y Cl z (Cl≥0), PbY 1‐ x Ca x Ba 2 Cu 3 O 7 F 2 , Sr 2 CuO 2 F x , CaCuO 2 F x , Sr 2‐ x A x CuO 2 F 2+δ (A=Ca, 0≤ x ≤2.0; A=Ba, 0≤ x ≤0.6), Sr 3 Ru 2 O 7 F 2 , LaSrMnO 4 F, and La 1.2 Sr 1.8 Mn 2 O 7 F . Typical F‐sources for their preparation were ClF 3 , F 2 , [NH 4 ]F, [NH 4 ]FHF, NF 3 , CuF 2 , ZnF 2 , AgF 2 , and NiF 2 .…”

“…The ( . [133] For example, YBa 2 Cu 3 O x F y Cl z (Cl � 0), [134][135][136][137][138][139][140] PbY 1-x Ca x Ba 2 Cu 3 O 7 F 2 , [141] Sr 2 CuO 2 F x , [142][143][144][145] CaCuO 2 F x , [144] [146][147][148] Sr 3 Ru 2 O 7 F 2 , [149] LaSrMnO 4 F, [150,151] and La 1.2 Sr 1.8 Mn 2 O 7 F. [150] Typical F-sources for their preparation were ClF 3 , [140] F 2 , [134,139,[141][142][143]145,146,150,151] [NH 4 ]F, [144,147] [NH 4 ]FHF, [138] NF 3 , [136,137] CuF 2 , [146,148,149] ZnF 2 , [135,146,148] AgF 2 , [146,148] and NiF 2 . [146,148] The fluoride incorporation of non-fluorinated superconductors was carri...…”

24 Conducting solids

“…Kirbyshire and Greaves have investigated the low temperature fluorination of PbYBa 2 Cu 3 O 7 to give the new phase PbYBa 2 Cu 3 O 7 F 2 . 161 The sample was shown to be superconductiing with T c # 30 K, which was raised to 50 K on partial substitution of Y by Ca.…”