HREM INVESTIGATIONS OF DEFECTS IN SINTERED YBA2CU3O7-DELTA

YBa//2Cu//3O//7 is studied using high resolution electron microscopy. Examples of the following defects are given: a planar stacking fault with a (CuO)//2 double layer instead of a CuO layer; antiphase boundaries, characterized by a displacement of c/3, whereby the APB plane is (103) or (101); edge dislocations with Burgers vectors of a left bracket 010 right bracket , a left bracket 001 right bracket , and (a/2) plus b/2 left bracket 001 right bracket ; left bracket 100 right bracket 90 degree rotation twins; (110) mirror twins; and oxygen vacancy ordering. The possible implications of these defects on the superconducting properties are discussed.