F. Trequattrini

Phase transitions and phase diagram of the ferroelectric perovskite ( Na 0.5 Bi 0.5 ) 1 − x Ba x TiO 3 by anelastic and dielectric measurements

The complex elastic compliance and dielectric susceptibility of

Stabilization of different conformers of bis(trifluoromethanesulfonyl)imide anion in ammonium-based ionic liquids at low temperatures.

{({\text{Na}}_{0.5}{\text{Bi}}_{0.5})}_{1\ensuremath{-}x}{\text{Ba}}_{x}{\text{TiO}}_{3}

Metal-insulator transition in Nd1−x Eux NiO3 probed by specific heat and anelastic measurements

(NBT-BT) have been measured in the composition range between pure NBT and the morphotropic phase boundary included,

Octahedral tilting, monoclinic phase and the phase diagram of PZT.

0\ensuremath{\le}x\ensuremath{\le}0.08

Fast oxygen mobility in tetragonal YBa2Cu3O7-x by anelastic relaxation measurements

. The compliance of NBT presents sharp peaks at the rhombohedral/tetragonal and tetragonal/cubic transitions, allowing the determination of the tetragonal region of the phase diagram, up to now impossible due to the strong lattice disorder and small distortions and polarizations involved. In spite of ample evidence of disorder and structural heterogeneity, the R-T transition remains sharp up to

Merging of the polar and tilt instability lines near the respective morphotropic phase boundaries of PbZr1−xTixO3

x=0.06

Interaction of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide with an electrospun PVdF membrane: Temperature dependence of the concentration of the anion conformers

, whereas the T-C transition merges into the diffuse and relaxorlike transition associated with broad maxima of the dielectric and elastic susceptibilities. An attempt is made at relating the different features in the anelastic and dielectric curves to different modes of octahedral rotations and polar cation shifts. The possibility is also considered that the cation displacements locally have monoclinic symmetry, as for PZT near the morphotropic phase boundary.

Anelastic spectroscopy study of the metal-insulator transition of Nd1−xEuxNiO3

The infrared absorption spectra of two ionic liquids with bis(trifluoromethanesulfonyl)imide (TFSI) as an anion and ammonium with different alkyl chains as cations are reported as a function of temperature. Using the comparison with ab initio calculations of the infrared-active intramolecular vibrations, the experimental lines were ascribed to the various ions composing the ionic liquids. In the liquid state of the samples, both conformers of the TFSI ion are present. In the solid state, however, the two conformers survive in N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI), while only cis-TFSI is retained in N-trimethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide (TMHA-TFSI). We suggest that the longer alkyl chains of the former compound stabilize the less stable conformer of TFSI by means of stronger interactions between anions and cations.

An Infrared Spectroscopy Study of the Conformational Evolution of the Bis(trifluoromethanesulfonyl)imide Ion in the Liquid and in the Glass State

Oxides RNiO3 (R = rare-earth, R ≠ La) exhibit a metal-insulator (MI) transition at a temperature TMI and an antiferromagnetic (AF) transition at TN. Specific heat (CP) and anelastic spectroscopy measurements were performed in samples of Nd1−xEuxNiO3, 0 ≤ x ≤ 0.35. For x = 0, a peak in CP is observed upon cooling and warming at essentially the same temperature TMI = TN ∼ 195 K, although the cooling peak is much smaller. For x ≥ 0.25, differences between the cooling and warming curves are negligible, and two well defined peaks are clearly observed: one at lower temperatures that define TN, and the other one at TMI. An external magnetic field of 9 T had no significant effect on these results. The elastic compliance (s) and the reciprocal of the mechanical quality factor (Q−1) of NdNiO3, measured upon warming, showed a very sharp peak at essentially the same temperature obtained from CP, and no peak is observed upon cooling. The elastic modulus hardens below TMI much more sharply upon warming, while the cooli...

Mechanisms of the semi-insulating conversion of InP by anelastic spectroscopy

Anelastic and dielectric spectroscopy measurements on PbZr(1-x)Ti(x)O(3) (PZT) close to the morphotropic (MPB) and antiferroelectric boundaries provide new insight into some controversial aspects of its phase diagram. No evidence is found of a border separating monoclinic (M) from rhombohedral (R) phases, in agreement with recent structural studies supporting a coexistence of the two phases over a broad composition range x<0.5, with the fraction of M increasing toward the MPB. It is also discussed why the observed maximum of elastic compliance appears to be due to a rotational instability of the polarization linearly coupled to shear strain. Therefore it cannot be explained by extrinsic softening from finely twinned R phase alone, but indicates the presence also of M phase, not necessarily homogeneous.A new diffuse transition is found within the ferroelectric phase near x ~ 0.1, at a temperature T(IT) higher than the well established boundary T(T) to the phase with tilted octahedra. It is proposed that around T(IT) the octahedra start rotating in a disordered manner and finally become ordered below T(T). In this interpretation, the onset temperature for octahedral tilting monotonically increases up to the antiferroelectric transition of PbZrO(3), and the depression of T(T)(x) below x=0.18 would be a consequence of the partial relief of the mismatch between the average cation radii with the initial stage of tilting below T(IT).