Abstract
Neutron diffraction was used to determine the structural properties of oxygen deficient for 0.09<δ<0.74. It was found that superconductivity disappears at the orthorhombic-to-tetragonal phase transition which occurs at =0.45. Structural parameters vary smoothly with δ but exhibit a change in slope at the orthorhombic-to-tetragonal transition. The structural properties exhibit the same features found in where =0.65. It is shown that the repulsion energy of oxygen atoms in the O(1) and O(5) sites in is smaller than in . This lower repulsion energy stabilizes the orthorhombic phase at lower values of δ. It is argued that the disappearance of superconductivity at the orthorhombic-to-tetragonal transition is an inherent property of the R (R denotes rare earth) system.
- Received 29 September 1989
DOI:https://doi.org/10.1103/PhysRevB.41.4173
©1990 American Physical Society