Synthesis and Structural Studies of the A-Site Substituted Bismuth Double Perovskites, Ba2-xSrxLuBiO6

Seventeen members of the solid solution series Ba 2 - x Sr x LuBiO 6 have been prepared, and their crystal structures were studied using a combination of powder synchrotron X-ray and neutron diffraction methods. The oxides all adopt a double perovskite-type A 2 BB‘O 6 (A = Ba, Sr; B = Lu, B‘ = Bi) structure as a consequence of ordering of the Lu 3+ and Bi 5+ cations. As the average ionic radius of the A-site cations (Ba/Sr) decreases the LuO 6 and BiO 6 polyhedra tilt and the structure changes from cubic Fm 3̄ m (0 < x < 0.375) through monoclinic I 2/ m (0.375 < x < 1.0) to monoclinic P 2 1 / n (1.0 < x < 2.0)