Direct observation of a new cationic vacancy ordered defect structure in laser-deposited superconducting YBaCuO thin films

The Y2Ba4Cu8O16 phase is the most common stacking defect observed in laser-deposited YBaCuO thin films. In this we report for the fist time, the existence of a cationic vacancy ordered Y2Ba4Cu8O16 structure in which every alternate pair of Cu atoms in the two chain layers are missing. This new structure is a polytype of the Y1Ba2Cu3O7 phase, i.e. it has the "Y2Ba4Cu8O16" structure but the "Y1Ba2Cu3O7" composition. Some possible causes and consequences of the formation of this defect structure are discussed. © 1990.