Superconductivity And Structure Of Infinite-Layer Compounds

The superconducting infinite-layer compound (Sr,Nd)CuO2 was synthesized under high pressure and its microstructure was characterized. The tetragonal structure a X a X c of the infinite-layer phase transforms into a superstructure 2 square-root 2a X 2 square-root 2a X c when the sample was in situ heated in a transmission electron microscope to about 600 K. An anomalous resistance change of the sample heated in vacuo to 400-degrees-C confirmed the phase transformation. After the superstructure formation, the sample lost its superconductivity and became semiconducting.