Structural phase transformation studies of the high Tc superconducting materials, Ba2RCu3O6+x, in air

To understand the crystal chemistry and to gain more insight into the effect of oxygen stoichiometry on superconductivity, the authors have investigated the phase transformations between the orthorhombic and tetragonal structures of several high Tc superconductors, Ba2RCu3O6+x, where R = Sm, Gd, Y, Ho and Er, and x=O to 1. Various techniques including X-ray diffraction, thermogravimetric analysis, neutron scattering, transmission electron microscopy, and determination of Meissner effect have been used to study the nature of the phase transition. The results of these studies are presented and discussed in this paper