Structural and magnetic transformation of La2−xBixCuO4 induced by electrochemical oxidation

Electrochemical oxidation of Bi-substituted phase La2−xBixCuO4 (x=0, 0.03 and 0.08) has been performed by using alkali metal hydroxide as an electrolyte. From X-ray Diffraction analysis, a structural transformation from orthorhombic to more distorted orthorhombic and to tetragonal could be observed for x =0 and 0.03, respectively, with c-axis elongation and unit cell expansion. The stabilization of excess oxygen in the crystal lattice, which has been confirmed by iodometry, leads to an increase of hole concentration (14% for x = 0 and 9% for x = 0.03) in CuO2 sheets with the superconducting transitions at 44K (x = 0) and 25K (x = 0.03).