The perovskite system La(Mg2/3Nb1/3)O-3 II. A neutron powder diffraction study

The crystal structure of the perovskite compound, lanthanum magnesium nioba te [La(Mg2/3Nb1/3)O-3 (LMN)] has been determined at 300 K by means of neutr on powder diffraction. Subsequent Rietveld refinement indicates that the cr ystal structure has monoclinic P2(1)/n symmetry, which is relatively uncomm on for oxide perovskites, ABO(3). An analysis of the structural data obtain ed reveals that this space group is uniquely capable of accommodating both BO6-octahedral tilting and cationic ordering. Consideration is also given t o the likelihood of further compositions adopting this symmetry, with some suggestions for future work on the pseudo-binary system Pb(Mg1/3Nb2/3)O-3-L a(Mg2/3Nb1/3)O-3 (i.e. PMN-LMN or; equivalently, PLMN). (C) 2000 Elsevier S cience Ltd. All rights reserved.