Copper deficiency in YBa2Cu3O7-x ceramics, textured and single crystals

Copper deficiency is studied in YBa2Cu3O7-δ phase. We compare polycrystals formed by sintering with textured and single crystals. The experimental method uses electron probe micro-analysis and X-ray structural determinations on single crystals. We show that YBa2Cu3O7-δ phase accommodates Cu deficiency up to several percent. Copper vacancies are located at the Cu(1) site (in the chains). Copper deficiency is evidenced when a liquid phase is involved in the chemical process. The implications of copper vacancies on the physical properties has probably to be reconsidered in future. (orig.)