“Ba6Nb4RuO18” and “LaBa4Nb3RuO15” – The structural consequences of substituting paramagnetic cations into AnBn−1O3n cation-deficient perovskite oxides

•B-cation deficient perovskite containing paramagnetic cations.•B-cation deficient structure determined by neutron powder diffraction.•Low ‘solubility’ of BaRuO3 in Ba5Nb4O15 leads to novel structure.

The B-cation deficient perovskite phases Ba6Nb4RuO18 and LaBa4Nb3RuO15 were prepared by ceramic synthesis. Neutron powder diffraction analysis indicates that rather than the 6-layer and 5-layer cation-deficient perovskite structures expected for these phases (by analogy to the known structures of Ba6Nb4TiO18 and LaBa4Nb3TiO15) they adopt 5-layer and 4-layer B-cation deficient perovskite structures respectively, and are better described as Ba5Nb3.33Ru0.81O15 and Ba3.16La0.84Nb2.36Ru0.72O12. The factors that lead to the compositionally analogous Nb/Ru and Nb/Ti phases adopting different structures are discussed on the basis of the difference between d0 and non-d0 transition metal cations.

Graphical abstractThe ruthenium-containing B-cation deficient perovskite phases, Ba5Nb3.33Ru0.81O15 and Ba3.16La0.84Nb2.36Ru0.72O12, adopt 5-layer and 4-layer structures respectively, rather than the 6-layer and 5-layer cation-deficient structures adopted by the analogous titanium-containing phases Ba6Nb4TiO18 and LaBa4Nb3TiO15.Figure optionsDownload full-size imageDownload as PowerPoint slide