TEM study on a new Sr-Cu-O phase synthesized under high pressure

A new Sr-Cu-O phase has been found as a minor phase in Sr ₂CuO _4-δ superconductor specimens synthesized under a high pressure of 5 GPa. Electron diffraction analysis reveals that it has a monoclinic unit cell with the parameters a=8.43 Å, b=11.1Å c=3.64 Å and β = 83.2°, and belongs to a space group Pm, P2 or P2/m. Based on the high-resolution transmission electron microscopic images and EDX compositional analysis which reveals the chemical formula SrCuO _y, a structural model of the space group of Pm is proposed for the phase. The simulated and the observed images are in reasonable agreement.