Crystal structure of high-Tc related NdBaCuO2BO3:: TEM and neutron powder diffraction study

The layered high-T-c related oxyborate NdBaCuO2BO3 has been investigated by ED, HREM and neutron powder diffraction. The crystal structure was refined using neutron data (space group P4bm, Z = 2, a = 5.52807(5) Angstrom, c = 7.44636(8) Angstrom; S = 0.981 R-p = 0.042, R-wp = 0.056, R-I = 0.030, R-F = 0.018). The main features of this structure are deformed (CuO5) square pyramids and triangular (BO3) groups which alternate along the 4-fold axis. Ba and Nd atoms are completely ordered and coordinated by 12 and 8 oxygen atoms, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.