HREM study of the crystal chemistry of the alkaline-earth cupric oxides stabilized at high pressure.

The crystal chemistry of the alkaline-earth cupric oxides stabilized at high pressure was studied by high-resolution electron microscopy. Two families of superconductors, (Ca1-ySry)1-xCuO2 and Srn+1CunO2n+1+delta (n = 1, 2), and one series of semiconductors, Srn-1Cun+1O2n, are reported. Their structural characteristics are systematically interpreted on the basis of the simple infinite-layer structure seen in SrCuO2. Microstructures and their relevance to high-Tc superconductivity are discussed, particularly in the alkaline-earth-deficient infinite-layer phase.