title: Structural study of K(x)Na(1 - x)NbO(3) (KNN) for compositions in the range x = 0.24-0.36.
abstract: The structure of the A-site substituted perovskite K(x)Na(1 - x)NbO(3), x = 0.24-0.36, where a phase boundary was previously reported, has been determined by high-resolution X-ray powder and neutron powder diffraction studies. The structure of the x = 0.3 compound was refined in the monoclinic space group Pm at 293 K and in P4mm at 523 K. The Glazer tilt system of the room-temperature monoclinic phase is a(0)b(+)c(0), which has implications for the nature of the next symmetry change with composition towards pure potassium niobate. A phase-coexistence region at the transition between monoclinic and tetragonal phases was also identified, consistent with a first-order phase boundary. There is also evidence for an intermediate oxygen-octahedra tilted tetragonal phase.
authors.affiliation: Department of Physics, University of Warwick, England. d.w.baker@warwick.ac.uk
authors.forename: D W
authors.initials: DW
authors.lastname: Baker
authors.forename: P A
authors.initials: PA
authors.lastname: Thomas
authors.forename: N
authors.initials: N
authors.lastname: Zhang
authors.forename: A M
authors.initials: AM
authors.lastname: Glazer