X-ray crystal structures of Al-doped (Y,Ca)Ba2Cu3O7-y whiskers

Al+3-doped (Y,Ca)Ba2Cu3O7-y (YBCO) whiskers have been synthesized using a solid-state reaction technique. These materials are promising candidates for solid-state THz applications based on sequences of Josephson Junctions (IJJs). Alumina addition was systematically varied and the effect of aluminium incorporation on the structure has been investigated using single-crystal X-ray diffraction. Aluminium only replaces Cu atoms in the O-Cu-O-Cu chains and a gradual transition from orthorhombic to tetragonal space group occurs, thus increasing the Al content. A gradual modification of the coordination sphere of the copper site has also been observed. The Ca2+ ion substitutes mainly the Y3+ ion and also, to a small extent, the Ba2+ ion.