Phase Transformation in the Infinite Layer Structure Compound(Sr, Nd) CuO₂ and its Effect on Superconductivity

Superconducting compound (Sr_0.86Nd_0.14) CuO₂ with the infinite layer structure was synthesized under high pressure. This tetragonal structure a x a transforms into a superstructure 2√2a x 2√2a when the sample was in situ heated in transmission electron microscope to about 600K. An anormalous resistance change of the sample during heating in vacuum to 400°C confirmed the phase transformation. After the superlattice formation, the sample lost its superconductivity and became semiconducting.