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.