INFLUENCE OF THE OXYGEN-CONTENT ON THE MI CROHARDNESS OF YBA2CU3O7-DELTA SINGLE-CRYSTALS IN THE TEMPERATURE-RANGE 77-293 K

The concentration dependence of the microhardness H-nu(delta) of the s ingle crystals YBa2Cu3O7-delta of two types has been studied in the te mperature range 77-293 K. It has been found that the microhardness inc reases linearly with decreasing temperature and the temperature depend ence of H-nu(T) is the stronger the less oxygen content. An analysis o f the results obtained shows that such H-nu(delta, T) behavior is defi ned not by changing the elastic properties of the crystals but by the effect of oxygen concentration and oxygen vacancies ordering on the co re structure and dislocations mobility which realize plastic deformati on in the vicinity of an indentation.