On the crystal structure of BaTbO3

The structure of perovskite-like BaTbO3 has been reinvestigated by high-resolution powder neutron diffraction at room temperature using HRPD at the ISIS Facility. It has been shown that neither the space group R (3) over barc nor Pnma describes correctly its structure. The profile refinement has demonstrated that BaTbO3 is tetragonal, space group I4/mcm, with the cell parameters a = 6.04832(4) Angstrom and c = 8.58569(10) Angstrom. This result is in agreement with the conclusions of Woodward, that the space group R (3) over barc is unlikely adopted by the A(2+)B(4+)O(3)-type perovskites. (C) 2002 Elsevier Science (USA).