Structural phase transition in YBa2Cu3O7−δ: the role of dimensionality for high temperature superconductivity

Some TEM investigations on composites, alloys-superalloys and superconductive ceramics

“…More precisely, for x close to 0, the compound is in the tetragonal phase while the orthorhombic phase is obtained for x close to 1. This reversible structural transition has already been studied by X-ray or electron diffraction [28,29]. Depending on the material, the temperature of the phase transition lies around 600-700 ° C. When looking at the structures of these compounds it is obvious that the phase transition results from the loss of the oxygen atoms lying in the CuO planes.…”

Polarized light and X-ray precession study of the ferroelastic domains of YBa2Cu3O7-?

“…In Fig. 6 we have transformed the a, b lattice parameters of YBCO from different authors [5,6,22,23] into the shear angle c~--90 ~ which permits comparison with other ferroelastics [24]. It is noteworthy that shear angles as small as 3 min of arc (Fe3BTO13I) or 10 min of arc (Gd2(MoO4)3) can lead to cracking if mutually perpendicular walls meet.…”

“…The change of crystal system at the phase transition necessarily requires the ferroic phase to be of ferroelastic character. The equi-translation nature of the transition [6] means that no antiphase-domains, generated by the phase transition, would be allowed [-7].…”

Epitaxially Induced Defects in Sr- and O-doped La2CuO4Thin Films Grown by MBE: Implications for Transport Properties

“…For instance, for the growth of ΥΒa2Cu3O7 (`123') under these conditions, the oxygen content of the cuprate is close to 6.0 instead of the required content of 7.0 [1]. On cooling the film under oxidizing conditions after growth, oxygenation takes place; this correlates with a volume change [2] as well as with a tetragonal-orthorhombic phase transition [3]. While only the compounds containing chains, such as YΒa 2 Cu3 O 7 , Y1-x Ρrx Βa2 Cu3 O 7 and LaΒa 2 Cu 3 O 7 , require a very large uptake of oxygen (approx.…”