Naohisa Takesue

X-ray diffuse scattering study of glass-like transition behavior of relaxor lead scandium niobate

Abstract Transition behavior of relaxor lead scandium niobate, Pb(Sc 1/2 Nb 1/2 )O 3 , has been investigated by means of an X-ray diffuse scattering technique. The results show simultaneous occurrence of freezing of ferroelectric and anti-ferroelectric fluctuations. Frustration between dipoles in the two states is suggested to be a mechanism of dielectric response of relaxors.

Lattice dimerization and strain in inorganic spin-Peierls compound NaV2O5

Abstract X-ray and neutron scattering experiments of the new inorganic spin-Peierls compound show that below T sp = 36 K an anomalous volume expansion is proportional to the superlattice intensity associated with lattice dimerization. Also reported is the pressure effect on this compound which undergoes a phase transition around 13 GPa (room temperature).

Lattice dynamics study on cubic barium titanate based upon a modified rigid-shell model

Abstract The rigid-shell model has been revisited in this paper for the lattice dynamics calculations in the paraelectric BaTiO3 since a few decades ago. The conventional harmonic models of Cowley et al. and Jannot et al., have been modified by including more interatomic force constants. The force constants were adjusted to fit the calculated phonon dispersion curves to the observed data from inelastic neutron scattering studies that were available in the literature. The calculated dispersions agree satisfactorily with the experimental results. Degeneracies of the phonon branches, as required by the crystal symmetry consideration, have been correctly reproduced for the first time. The fitting parameters of our model have values whose trends are seen to have similar behavior to the previous models. Moreover, the newly employed parameters have shown interesting features related to the short-range, non-Coulombic interactions of the ions.