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

Structural variations in crystals for Tl-Ba-Ca-Cu-O oxides with Tc above 100 K were examined by an electron microscope. Common phases for these oxides were found to be Tl2Ba2CaCu2O8+x and Tl2Ba2Ca2Cu3O10+x. Variations in these structures result from multiplicity in (CuO2-Ca-CuO2)×n slab (designated CCn with n=integer), whose composition is represented by Tl2Ba2CanCun+1O2(3+n)+x. It is shown, for the first time, that slab thicknesses CCn 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.