Synthesis, characterization, phase diagrams and superconducting and normal state magnetic properties of La{sub 2-x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.08) and electrochemically oxidized La{sub 2-x}Sr{sub x}CuO{sub 4+{delta}} (0 {le} x {le} 0.33, 0 {le} {delta} {le} 0.12)
La{sub 2-x}Sr{sub x}CuO{sub 4}(0{le}x{le}0.15) can all be intercalated with oxygen by a novel electrochemical oxidation method. Bulk superconductivity is found with an onset {Tc} {approx} 40 K for the whole range 0.01 {le} x {le} 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility x(T = 50-320 K) data for La{sub 2}CuO{sub 4.11} and La{sub 1.92}Sr{sub 0.08}CuO{sub 4.07} are nearly identical with those of conventionally prepared La{sub 1.85}Sr{sub 0.15}CuO{sub 4}, indicating that the hole doping level (p) in the CuO{sub 2} planes of the three compounds is nearly the same. Combined thermogravimetric analysis and iodometric titration experiments indicate that part of the intercalated oxygen has a formal valence close to -1. The maximum doped-hole concentration in the CuO{sub 2} planes that can be achieved from combined Sr-doping and electrochemical oxygen doping for 0 {le} x {le} 0.15 is p {approx} 0.16 holes/formula unit. Oxygen can also intercalate into single crystal La{sub 2}CuO{sub 4} through a slow electrochemical oxidation process. The required low current and long time for the charging process reflects that the oxygen intercalation for a single crystal is limited by its small specific surface area and long diffusion distance. The anisotropic superconducting, magnetic and transport properties are summarized and compared with those of polycrystalline La{sub 2}CuO{sub 4+{delta}} as well as of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4} single crystals. The single crystal La{sub 2}CuO{sub 4+{delta}} has a maximum {Tc} {approx} 40 K, which is lower than that ({Tc} {approx} 42-45) of the corresponding polycrystalline samples.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames, IA (United States)
- OSTI ID:
- 111258
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
Similar Records
Phase separation and finite size scaling in La[sub 2[minus][ital x]]Sr[sub [ital x]]CuO[sub 4+[delta]] [0[le]([ital x],[delta])[le]0. 03]
Evolution and the concomitant disappearance of high- Tc superconductivity with carrier concentration in the La sub 2 minus x Sr sub x CuO sub 4 minus. delta. system (0. 0 le x le 1. 2): Crossover from a Mott insulator to a band metal