SYNTHESIS AND SUPERCONDUCTIVITY OF ND0.7SR1.3CU(O,F)(4-DELTA) WITH T-C=44 K

Superconducting cuprate fluorides Nd0.7Sr1.3Cu(O,F)(4-delta) with T-c = 44 K were obtained by solid phase fluorination of the T-structure Nd 0.7Sr1.3CuO4-gamma at low temperature (200-300 degrees C) using CuF2 a s fluorinating reagent. The oxyfluoride has K2NiF4 structure with S.G. I4/mmm as its precursors, but the evident lattice expansions were obs erved. The a-axis expands from 3.7257(2) Angstrom to 3.9288(5) Angstro m and c-axis from 12.8240(3) Angstrom to 12.9630(2) Angstrom. No trace of SrF2 was detected in these fluorinated products. XRD and magnetic measurement revealed that the superconductivity in the fluorinated pro ducts originated from the oxyfluorides with reduced CuO2 plane and in the presence of the apical anion.