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Abstract We report the structural, dielectric, elastic, ferroelectric and ferromagnetic properties of multiferroic (Nd, Fe)-doped PbTiO3 perovskite ceramics with composition (Pb 0.88 Nd 0.08)(Ti 0.94 Fe 0.04 Mn 0.02)O 3 , prepared by different solid state reaction methods: the first one based on a single-stage calcination (Method I) and the second based on a double-stage calcination (Method II). Structural, dielectric and anelastic measurements evidenced a double phase transition for samples prepared by Method I, which has been attributed to phase separation. This phase separation has been confirmed also by TEM and HRTEM investigations. Samples prepared by Method II showed a single phase transition from paraelectric to ferroelectric phase. We found coexistent ferroelectric and ferromagnetic properties, also at room-temperature, but only for ceramics prepared by Method II. The crucial role of calcination process for avoiding phase separation and obtaining homogeneous structures with ferroelectric and ferromagnetic order is underlined. [ABSTRACT FROM AUTHOR]

The western Caribbean, a subarea of the Caribbean Sea Large Marine Ecosystem, includes the Mesoamerican Barrier Reef System, the Yucatan Basin, the Cayman Basin and the Yucatan Channel. Here we discuss the main oceanographic features of the western Caribbean Sea and present some examples of marine resources distributed throughout the western Caribbean Sea LME subarea along different spatial scales. Particular attention is given to their planktonic stages when physical oceanographic features (such as eddies and gyres, or current systems) can operate either as forces that promote larval dispersal or as barriers enhancing larval retention, as this determines their connectivity. Bluefin tuna, the early life stages (eggs and larvae) of reef fish, the Caribbean Spiny lobster, and the Queen conch are presented as examples. Dispersal distances depend on the oceanographic phenomena, with larger dispersals expected where intense currents occur, such as in the Yucatan Current. Conversely, retention can be expected in the presence of gyres such as the Honduras Gyre and Yucatan Basin eddies. There is a growing body of evidence supporting the need for a multi-scale approach in order to understand the complexity of LMEs. Moreover, the connectivity between regions in the western Caribbean Sea LME subarea, as shown by the exchange of marine resources and physical oceanographic processes, requires an international policy that supports collaborative efforts to monitor the dynamics of coastal and oceanic habitats together with marine resources. [ABSTRACT FROM AUTHOR]

Abstract: A revival of the interest on the morphotropic phase boundary of the O3 started after a neutron diffraction study revealed the existence of a monoclinic phase (M) bridging the tetragonal (T) and rhombohedral (R) ones. In addition, the M phase has been found to exhibit a low temperature transformation, possibly involving rotations of the oxygen octahedra, raising a debate on its nature. Finally, the rotational instability has been predicted to extend also in the T phase. We present measurements of the complex dielectric susceptibility and elastic compliance of with which bring new information on the low temperature phase transformations. The T–M transition gradually changes from first- to second-order increasing the Ti content from the boundary with the R phase to , confirming that the coexistence of T and M phases found by neutron diffraction is intrinsic and not due to compositional fluctuations. Strikingly, the T–M transformation causes a peak in the elastic compliance, whose amplitude may even exceed that of the jump at the cubic-to-tetragonal transition, as if it were a ferroelastic transformation; it is shown that indeed there is linear coupling between shear strain and order parameter, when the T–M transition mainly consists of a rotation of the polarization. The instability involving rotation of the octahedra below 200K is visible both in the dielectric and anelastic losses, and it extends in the tetragonal phase, as predicted by recent first-principle calculations. [Copyright &y& Elsevier]

Abstract: A detailed study of the relaxation process occurring in polycrystalline ZrV2H x (0≤ x ≤1) below room temperature has been carried out by means of acoustic spectroscopy. At low H concentrations the main effect is due to the well known martensitic phase transformation around 120K. Moreover a H-related thermally activated peak is detected around 240K, at a vibration frequency of about 3.5kHz. The peak features and the relaxation parameters are discussed in terms of the possible kinds of H dynamic giving rise to the anelastic effect. For the highest values of x a clear effect due to H ordering is visible around 200K. In addition, a new thermally activated process is detected around 140K and the experimental data can be satisfactorily fitted with the superposition of two broad peaks with activation energies of 0.14 and 0.17eV. These processes are due to the jumps of H atoms, likely among tetrahedral interstitial sites in the lattice of the Laves phase. [Copyright &y& Elsevier]

Abstract: The anelastic spectrum of two intermetallic polycrystalline ZrV2H x samples (0≤ x ≤0.09) has been investigated from 1 to 600K in the frequency range 2–50kHz. Besides the well-known martensitic phase transformation around 120K, two thermally activated peaks are detected in the H doped alloys around 230 and 410K at a vibration frequency of about 3kHz. The process at the lower temperature is due to the jumps of H atoms likely among tetrahedral interstitial sites in the cubic lattice of the Laves phase. The profile can be satisfactorily fitted with the superposition of two peaks, broader than single time Debye relaxations, with activation enthalpies of 0.33 and 0.41eV. The peak above room temperature, which appears only on the sample containing impurity phases (primary solution phase of vanadium and zirconium), presents features which suggest a mechanism involving the interaction between point defects and dislocations. [Copyright &y& Elsevier]

Abstract: We present the results of anelastic relaxation experiments (2–30 kHz) on ceramic SrTiO3 subjected to reduction in H2 atmosphere, which yields a balance between oxygen vacancy (VO) and (OH)− defects. The resulting anelastic spectrum contains, besides the well known structural transformation near 110 K, several thermally activated relaxation processes between 200 and 700 K. The two main elastic energy loss peaks are proposed to provide the first measurement of the hopping rate of VO and (OH)− defects in pure SrTiO3. [Copyright &y& Elsevier]

Abstract: We present the results of anelastic relaxation experiments (2–30kHz) on ceramic SrTiO3 subjected to reduction in H2 atmosphere, which yield a balance between VO and (OH)− defects. The resulting anelastic spectrum contains, besides the well-known structural transformation near 110K, several thermally activated relaxation processes between 200 and 700K. The two main elastic energy loss peaks are proposed to provide the first measurement of the hopping rate of VO –(OH)− defects in pure SrTiO3. [Copyright &y& Elsevier]

Abstract: We report extended X-ray absorption fine structure (EXAFS) measurements at the Mn K edge and magnetic measurements performed on (La1−x Ca x )(Mn1−y M y )O3 samples (M=Cr or Ni; x=0.37 and 0.75 and y=0.03 or 0.08). The Mn substitution produces important effects on both the sides of the LaMnO3–CaMnO3 phase diagram. For x<0.5 the ferromagnetic–metallic phase maintains its main character even after Mn substitution, but both the doping species (Ni or Cr) lower T C and broaden the magnetic transition, and the EXAFS study evidences two Mn–O distances, suggesting the presence of zones of distorted insulating phase. For x>0.5, after the doping with Cr, the charge ordered phase persists but on a shorter scale, whereas the Jahn–Teller distortion is weakened as indicated by EXAFS measurements, and the formation of ferromagnetic clusters is evidenced by magnetic measurements. EXAFS and magnetic measurements are in mutual agreement, thus confirming the correlation between the local disorder determined by charge localization and magnetic degrees of freedom. [Copyright &y& Elsevier]

The high-temperature anelastic spectrum of the solid solution Sc–O has been investigated on a polycrystalline sample at oxygen concentrations between 0.024 and ∼0.9 at.% O, as estimated by residual resistivity and intentional O doping. Two thermally activated relaxation processes appear near 430 and 520 K for a vibration frequency of 3.5 kHz; both peaks are stable with thermal cycling and their intensities increase with the oxygen content, indicating that they are due to O jumps. The process at lower temperature has an intensity that strongly increases with increasing temperature, when measured at higher frequency (42 kHz), indicating that the relaxation occurs between states differing in energy by ∼0.3 eV. The peak is describable by a single relaxation time, and is interpreted as due to the stress-induced hopping of single oxygen atoms between the non-equivalent tetrahedral and octahedral interstitial sites. The process at high temperature is tentatively attributed to O pairs. An estimate of the specific resistivity of O atoms has been provided. [Copyright &y& Elsevier]

The complex dynamic Young''s modulus of ceramic Nd2−xCexCuO4 with x=0, 0.05 and 0.20 has been measured from 1.5 to 100 K at frequencies of 1–10 kHz. In the undoped sample the modulus starts decreasing below ∼20 K, instead of approaching a constant value as in a normal solid. The modulus minimum has been interpreted in terms of paraelastic contribution from the relaxation of the Nd3+ 4f electrons between the levels of the ground state doublet, which is split by the interaction with the antiferromagnetically ordered Cu sublattice. The value of the splitting is found to be 0.34 meV, in excellent agreement with inelastic neutron scattering, infrared and specific heat experiments. With doping, the anomaly shifts to lower temperature and decreases in amplitude, consistently with a reduction of the local field from the Cu sublattice. [Copyright &y& Elsevier]

• NBT-BT-PVDF flexible lead-free piezoelectric composite films were prepared by hot pressing. • Hot pressing method transforms PVDF α-phase into electro-active β and γ phases. • The dielectric permittivity increases with the active phase amount increase, up to 80. • Notable properties both for energy storage and energy harvesting application found. • Testing of force impact: up to 9 V and ~ 81 μW of output voltage and power obtained. [Display omitted] The idea of this work is finding the way to efficiently and safely use mechanical energy released in small quantities around us to power up small-scale electronic devices used in everyday life. To this purpose, flexible lead-free piezoelectric composite films were prepared by hot pressing. Different amounts (30, 35 and 40 vol%) of lead-free piezoelectric material bismuth sodium titanate-barium titanate were embedded in the matrix of polyvinylidene fluoride under carefully optimized conditions of temperature and pressure, obtaining flexible films with quite homogeneous distribution of piezo-active filler. ATR-FTIR analysis revealed that hot pressing the flexible films caused a transformation of electro-inactive PVDF α-phase into electro-active β and γ phases. Dielectric measurements showed an increase of the permittivity up to 80 with the active phase increasing. Anelastic measurements showed that the elastic modulus increases as well with the fraction of active ceramic phase. Lastly, obtained flexible polymer-composites demonstrated notable properties both for energy storage and energy harvesting application, showing up to 74% of energy storage efficiency and, from testing of the force impact, up to 9 V and ~ 80 μW of output voltage and power. [ABSTRACT FROM AUTHOR]