A-site deficient perovskites in the SrO–ZrO2–Nb2O5 system: Composition dependent structures from neutron powder diffraction data

A series of A-site deficient perovskite-type phases was synthesised and characterised in the SrO–ZrO2–Nb2O5 system. The composition range was established as Sr0.70+xZr0.40+2xNb0.60−2xO3, ∼0.02≤x≤0.30, and the resulting structures refined using high resolution neutron powder diffraction data. While structures in this composition range are closely related to the cubic perovskite parent, the symmetry for all investigated compositions is lowered to tetragonal or orthorhombic. For x<0.15 the resulting space group is tetragonal I4/mcm, for x>0.15 it is orthorhombic Pnma and for x=0.15 two phases co-exist, in space groups I4/mcm and Pnma.