Stabilization of orthorhombic Ba2YCu3O7 − δ phase by the 5a group transition metal elements

Abstract The effect of partial replacement of copper atoms in the superconducting orthorhombic Ba 2 YCu 3 O 7 − δ phase with the 5a group transition metal elements has been studied. It was shown that in the Ba 2 YCu 3 M x O 7 − δ ( M ≡ V , Nb or Ta ) system, the orthorhombic phase is stabilized in a wide range of dopant concentrations. A degradation of superconducting properties takes place gradually by increasing the dopant level, this being accompanied by formation of the other phases, i.e. BaVO 3 , Ba 3 V 2 O 8 , Ba 2 YNbO 6 , Ba 2 YTaO 6 and CuO. X-ray powder diffraction, electron paramagnetic resonance spectroscopy, low field non-resonant microwave absorption, electrical resistance and magnetic susceptibility measurements were correlated.