Oxygen content and structure of Ba sub 2 YCu sub 3 O sub 7 below 525C.

The relationship between the crystal structure and oxygen content was established for Ba sub 2 YCu sub 3 O sub x ceramic. Samples whose initial values of x were either 6.98 (orthohombic structure) or 6.16 (tetragonal structure) were annealed side by side at 380 to 525C in flowing nitrogen containing a fixed, small amount of oxygen. The powders were heated until their weights stabilized and this required very long times at the lower temperatures. The room temperature structure and x were determined for these samples. X-ray diffraction was also used to determine the structure of powders with intermediate x while the samples were heated using conditions which prevented any a change in oxygen content.