The crystal structure of the B-site ordered complex perovskite Sr(Yb0.5Nb0.5)O-3

The room-temperature crystal structure of the B-site ordered complex perovs kite strontium ytterbium niobate, Sr(Yb0.5Nb0.5)O-3 [monoclinic, Z = 2, P2( 1)/n (set 2), a = 5.79095(8), b = 5.82210(7), c = 8.20358 (12) Angstrom, be ta = 90.126 (1)degrees, with final R-wp = 0.0595, R-Bragg = 0.0203 for the neutron profile and R-wp = 0.0832, R-Bragg = 0.0193 for the X-ray profile, respectively], was determined by X-ray powder diffraction, high-resolution neutron powder diffraction and transmission electron microscopy. This compo und shows a slight triclinic distortion from the prototype doubled cubic pe rovskite cell as a result of an a(-)a(-)c(+)-type oxygen octahedral tilting distortion. It is also shown that the site ordering of the different speci es of B-site cations, Yb3+ and Nb5+, inherently leads to a difference betwe en the volumes of the YbO6 and NbO6 octahedra. This volume difference is sh own to inevitably inhibit the rigid rotation of octahedra.