Crystal Structure Variations due to Multiplicity in CuO2-Ca-CuO2 Slabs in Superconductive Tl-Ba-Ca-Cu-O Oxides

Abstract

Structural variations in crystals for Tl-Ba-Ca-Cu-O oxides with T _c above 100 K were examined by an electron microscope. Common phases for these oxides were found to be Tl₂Ba₂CaCu₂O_8+x and Tl₂Ba₂Ca₂Cu₃O_10+x . Variations in these structures result from multiplicity in (CuO₂-Ca-CuO₂)×n slab (designated CC _n with n=integer), whose composition is represented by Tl₂Ba₂Ca _n Cu _n+1O_2(3+n)+x . It is shown, for the first time, that slab thicknesses CC _n have been observed for structures with n=1 to 6. The structural variation is also caused by two kinds of BaO-TlO-BaO and BaO-TlO-TlO-BaO slabs.