Search

Multiferroic (BiLaFeO)(PbTiO) ceramics with x = 0, 0.1, 0.2, 0.3 and 0.5 was prepared from mechanochemically synthesized nanopowders. The XRD studies revealed the tetragonal structure for x ≤ 0.2 and rhombohedral for x = 0.5 with mean grain sizes from 15 to 28 nm. Dielectric response of the compounds in the temperature range 125-525 K was found to contain two anomalies: at ~400 K attributed to the presence of oxygen vacancies and that below 300 K characteristic of ferroelectric relaxors; the Curie point anomaly was apparent at 500 K only for samples with x = 0.5. Analysis of the low-temperature response enabled us to characterize the relaxor state of the solid solution and to yield information on the decrease in the activation energy of dipole moment flipping in polar nanoregions. Magnetic studies revealed two contributions to the magnetization of the nanoceramics pointing to a coexistence of weak ferromagnetic and antiferromagnetic orderings in the range 4 ÷300 K. Low temperature variation of the magnetization in field-cooling and zero-field-cooling conditions revealed spin glass behavior which in (BiLaFeO)(PbTiO) is dependent on x. Moreover, a sharp step in magnetization at ~250 K was found to be dependent on the La content and related to the A-site distortion leading to a modification of Fe-O-Fe angles and antiferromagnetic coupling between magnetic Fe moments. [ABSTRACT FROM AUTHOR]

The relationship between the molecular and crystalline structure and the dielectric response of hot-pressed PVDF film and the films cast from N,N-dimethylacetamide solution was studied by means of wide angle X-ray scattering, Raman and dielectric spectroscopy. We have found that the degree of crystallinity of hot-pressed PVDF is by about 10% higher than that of solution-cast films, which results in a decrease in the activation energy of segmental motions and a rise in the freezing temperature. We have also observed that the solution-cast samples are more reach in sequences containing trans conformation (T)nG with n ≥ 3 which leads to an increase in their permittivity value. [ABSTRACT FROM AUTHOR]

The results of dielectric response studies of the biocellulose show that two relaxation processes can be distinguish: the local main chain motion at ˜200 K and an orientational motion in a mixed phase of polysaccharide and water at ˜325 K. The electroacoustic parameters of a loudspeaker with biocellulose membrane were measured in echoless conditions. The relationship between dielectric and mechanical properties of biocellulose was found. [ABSTRACT FROM AUTHOR]

Preliminary results of polymer poly(ethylene oxide) (PEO) with β-LiNH4SO4 (LAS) or Li(N2H5)SO4 (LHS) composites are presented. It was shown that Raman spectra did not reveal the existence of any complexes in the composites under studies. Electrical conductivity of the composites with LAS is about one order of magnitude higher than that for PEO and two orders higher than for LAS at room temperature, whereas for composites with LHS conductivity is lower than for LHS crystals. [ABSTRACT FROM AUTHOR]

Ferroelectric copolymers of vinylidene fluoride and trifluoroethylene irradiated with fast electrons were found to exhibit dispersive dielectric response, characteristic of ferroelectric relaxors and giant electrostriction. Here we report the results of our ESR, IR and Raman spectroscopy studies of radiation damage to the copolymers and relate the effects to the conformational disorder and dispersive dielectric response. [ABSTRACT FROM AUTHOR]

Diffuse X-ray scattering studies were performed for as grown Pb(Sc½Nb½)O3-PSN, Pb(Sc0.5Ta0.5)-PST and Pb(Sc0.5Nb0.2Ta0.3 )O3-PSNT single crystals at 400 K by means of a four-circle single crystal diffractometer equipped with CCD area detector. The superstructure observed yields a cubic unit cell with lattice parameter equals to 0.8181 nm, 0.8150 nm and 0.8140 nm for PSN, PST and PSNT crystals, respectively. The analysis of the extinction rules of diffuse reflections, observed for all the crystals in the superparaelectric phase, leads to a space group Pn&3macr;m instead of the Fm3m space group ascribed previously. [ABSTRACT FROM AUTHOR]

(NH 4 ) 3 H(SO 4 ) 2 , a member of M 3 H(XO 4 ) 2 hydrogen-bonded crystal family. The transition from the superionic phase (R &3macr; m) to the low-temperature phase (A2/a) at T s =413 K is accompanied by an anisotropic spontaneous deformation, which leads to the appearance of ferroelastic properties. The paper presents results of temperature variation of heat capacity, ferroelastic domain pattern and NIR Raman spectra in the close vicinity of T S . [ABSTRACT FROM AUTHOR]