The perovskite system La(Mg2/3Nb1/3)O3: II. A neutron powder diffraction study

The crystal structure of the perovskite compound, lanthanum magnesium niobate [La(Mg2/3Nb1/3)O3 (LMN)] has been determined at 300 K by means of neutron powder diffraction. Subsequent Rietveld refinement indicates that the crystal structure has monoclinic P21/n symmetry, which is relatively uncommon for oxide perovskites, ABO3. An analysis of the structural data obtained reveals that this space group is uniquely capable of accommodating both BO6-octahedral tilting and cationic ordering. Consideration is also given to the likelihood of further compositions adopting this symmetry, with some suggestions for future work on the pseudo-binary system Pb(Mg1/3Nb2/3)O3–La(Mg2/3Nb1/3)O3 (i.e. PMN–LMN or, equivalently, PLMN).