Octahedral Tilting and Cation Ordering in Perovskite-Like Ca4Nb2O9=3bulletCa (Ca1/3Nb2/3)O3 Polymorphs

A quaternary oxide, Ba2YbTaO6, was prepared, and its powder X-ray diffraction measurements and the Rietveld analysis show that it is cubic with the space group Fm m and that Yb3+ and Ta5+ ions are structurally ordered. Magnetic susceptibilities of Ba2YbTaO6 were measured in the temperature range between 5 K and room temperature, and the electron paramagnetic resonance (EPR) spectrum of Yb3+ ion doped in Ba2LuTaO6 was measured at 8 K. This compound is paramagnetic down to 5 K, and the temperature dependence of its susceptibility was analyzed with the crystal field model. Hyperfine interaction was observed for the EPR spectrum of Yb3+/Ba2LuTaO6. Analysis of the EPR data indicates the existence of the covalency in the Yb3+ ion in an octahedral symmetry.