New approach to the fabrication process of bulk high-T-c superconducting oxide materials with strong pinning of magnetic flux

A new approach to the fabrication process of bulk HTSC materials is propose d, using the initial mixture of components (YBa2Cu3O7-x and non-superconduc ting inclusions) in the form of nanocrystalline powders. The preparation of ultra-fine powders is by means of the pulse-plasma channel method, which a llows metallic, oxide and alloy materials etc (including HTSC) to be disper sed into spherical particles of 20-200 nm size. Bulk specimens of YBa2Cu3O7 -x (d similar to 250 nm) + 2% ZrO2 (d similar to 70 nm) were produced by pu lling the initial mixed powders through a gradient furnace. The results of structural, magnetic, and magneto-optical measurements are reported for the powders and the bulk samples. The critical current density, j(c), of the b ulk composites range from 10(4) to 2 x 10(4) A cm(-2) at 77 K in zero magne tic field. The magnetic measurements and magneto-optical observations revea l that j(c) is independent of direction in the composite and corresponds to the transport current through the whole sample. The mean distance between pinning sites coincides with the mean grain size of YBa2Cu3O7-x, which conf irms homogeneous distribution of the inclusion particles.