The parent structure of the layered high T sub c compounds, (Ca sub (0.86) Sr sub (O.14) CuO sub 2.

Crystals of composition (Ca sub (0.86) Sr sub (0.14)) CuO sub 2 have been grown and characterized by single crystal X-ray diffraction. The crystals are tetragonal with space group P4/mmm (No. 123), a=3.8611(2)angstroms, c=3.1995(2)angstroms, c/a=0.829, Z=1. The structure contains planar [CuO sub 2]inf layers separated by Ca (Sr) atoms. The structure is a simple defect perovskite with ordered oxygen vacancies and can be regarded as the n = inf parent of the A sub 2 B sub 2 Ca sub (n-1) Cu sub n O sub (4+2n) (A = Bi, T1; B = Sr, Ba) superconductors.