SYNTHESIS, ELECTRICAL AND MAGNETIC-PROPERTIES OF NANOCRYSTALLINE AGXHGBA2CUO4+DELTA (X=0,0.02) SUPERCONDUCTORS

Nanocrystalline HgBa2CuO4+delta and Ag0.02HgBa2CuO4+delta compounds are synthesized from the precursor Ba2CuO3, HgO and Ag2O by a solid-state reaction. Ag addition to HgBa2CuO4+delta does not change the lattice structure but about 1% reduction in cell volume is observed. The crystallite size of both compounds are similar to 100 nm. The superconducting transition temperature is the same (95 +/- 0.5 K) for both compounds but a different transition shape and width are observed. Ag0.02HgBa2CuO4+delta shows an electrical conductivity enhanced by a factor of 7 compared to HgBa2CuO4+delta. The J(c intra) calculated from the magnetization data is similar to 10(6) A/cm(2) around liquid-nitrogen temperatures. The temperature and magnetic-field-dependent variation of J(c intra) of Ag0.02HgBa2CuO4+delta below a certain critical temperature and magnetic field indicate that the flux-creep model may not be applicable in certain field and temperature ranges.