Structural changes of relaxor ferroelectric SrBaNbO (SBN52) on quenching and reheating.

Quenching of SrBaNbO (SBN52) from temperatures above 700°C causes small modifications in the strontium distribution over the large cation sites (Me1 and Me2), changed off-centre shifts of the Nb atoms and slightly increased modulation amplitudes. The higher disorder of cation incorporation can explain the enhanced ferroelectric properties. The quenched structural disorder can be healed by reheating followed by slow cooling.

Incommensurate modulations of relaxor ferroelectric Ca0.24Ba0.76Nb2O6 (CBN24) and Ca0.31Ba0.69Nb2O6 (CBN31).

CBN crystals show a one- and a two-dimensionally modulated modification. The former is isotypic with orthorhombic Ba4Na2Nb10O30 and the latter with the tetragonal tungsten bronze type of crystal structure. The orthorhombic form irreversibly transforms to the tetragonal polymorph at the ferroelectric phase transition near 603 K.

Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28).

The incommensurately modulated crystal structures of Ca(0.28)Ba(0.72)Nb(2)O(6) (CBN28) and Ce(0.

Modulated crystal structure of incommensurate low tridymite.

The incommensurately modulated crystal structure of low SiO2 tridymite was refined based on single-crystal X-ray diffraction data in the superspace group Cc(alpha0gamma)0. The data set consists of 885 main reflections, 1751 first-order, 924 second-order and 119 third-order satellite reflections with I > 3sigma(I). The modulation is mainly made up from cooperative twistings of the rigid SiO4 tetrahedra.

Structure of strontium barium niobate SrxBa1-xNb2O6 (SBN) in the composition range 0.32

The structure of strontium barium niobate crystals SrxBa1-xNb2O6 is comprehensively studied in the whole range of the tetragonal tungsten bronze phase (x=0.32-0.82) using both powder and single-crystal X-ray diffraction measurements.

Zn location in the W-type hexagonal ferrite SrZnCoFe16O27.

The title compound, SrZnCoFe(16)O(27) (ZnCo-W), strontium zinc cobalt hexadecairon oxide, crystallizes in space group P6(3)/mmc, with the Sr atom at a site with -6 m 2 symmetry and Zn(2+) located at two tetrahedral sites (4e and 4f, each with 3m symmetry) of the spinel blocks. The Zn occupancy is 36% on equipoint 4e and 14% on 4f. The enrichment of diamagnetic ions on one of seven sublattices is thought to be responsible for the high temperature dependence of the saturation magnetization.

Monoclinic AlPO4 tridymite at 473 and 463 K from X-ray powder data.

Upon cooling from its hexagonal high-temperature modification, AlPO4 (aluminium phosphate) tridymite successively transforms to several displacively distorted forms, including a normal structure-incommensurate-lock-in phase transition sequence. The space-group symmetries in this series are P112(1), P112(1)(alphabeta0) and P2(1)2(1)2(1), respectively. The distortion pattern of the intermediate P112(1) phase can be described as alternate shifts of adjacent layers of tetrahedra coupled with tilting of the tetrahedra.