title: Structural and dielectric studies of the phase behaviour of the topological ferroelectric La1-xNdxTaO4.
abstract: The layered perovskite LaTaO(4) has been prepared in its polar orthorhombic polymorphic form at ambient temperature. Although no structural phase transition is observed in the temperature interval 25° C < T < 500 °C, a very large axial thermal contraction effect is seen, which can be ascribed to an anomalous buckling of the perovskite octahedral layer. The non-polar monoclinic polymorph can be stabilised at ambient temperature by Nd-doping. A composition La(0.90)Nd(0.10)TaO(4) shows a first-order monoclinic-orthorhombic (non-polar to polar) transition in the region 250° C < T < 350 °C. Dielectric responses are observed at both the above structural events but, despite the 'topological ferroelectric' nature of orthorhombic LaTaO(4), we have not succeeded in obtaining ferroelectric P-E hysteresis behaviour. Structural relationships in the wider family of A(n)B(n)X(3n+2) layered perovskites are discussed.
authors: EaStCHEM and School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, UK. pl@st-and.ac.uk.
authors: Keith J
authors: KJ
authors: Cordrey
authors: Magda
authors: M
authors: Stanczyk
authors: Charlotte A L
authors: CA
authors: Dixon
authors: Kevin S
authors: KS
authors: Knight
authors: Jonathan
authors: J
authors: Gardner
authors: Finlay D
authors: FD
authors: Morrison
authors: Philip
authors: P
authors: Lightfoot