EFFECT OF CA DOPING ON THE STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF EUBASRCU3O7-DELTA

The effect of Ca doping in EuBaSrCu3O7-delta has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measu rements. X-Ray diffraction analyses of the samples showed that up to 3 0 at.% Ca can be substituted for Sr in EuBaSrCu3O7-delta, which has or thorhombic symmetry. The orthorhombicity decreases with increase in x in EuBaSr1-xCax Cu3O7-delta, the material becoming tetragonal at x = 0 .2. Ac susceptibility and de electrical resistivity measurements as fu nction of temperature from 10 to 300 K showed that the superconducting transition temperature T-c decreases monotonically from 84 to 75 K as the Ca concentration x increases from 0.0 to 0.3. The decrease in T-c can be attributed to the structural change taking place in EuBaSrCu3O 7 as a consequence of replacement of Sr by Ca.