The temperature evolution of the structure of NaNO(2) nanocomposite ferroelectric material in a porous glass with 7 nm pores was studied by neutron diffraction in temperature region from room temperature up to the melting, i.e. in the... more
The temperature evolution of the structure of NaNO(2) nanocomposite ferroelectric material in a porous glass with 7 nm pores was studied by neutron diffraction in temperature region from room temperature up to the melting, i.e. in the ferro- and paraelectric phases. It is demonstrated that in the ferroelectric phase the structure is consistent with the structure of the bulk, but above the ferroelectric phase transition (and up to approximately 513 K) a volume premelted state is formed, manifesting itself in a growth of amplitudes of ion thermal vibrations, a steep increase of elementary cell volume and "softening" of lattice. For the first time the temperature dependence of order parameter eta for confined sodium nitrite is determined. eta (T) follows a power law with T(C)=425.6+/- 2.1 K and beta= 0.31+/- 0.04, which is essentially different from that for bulk NaNO(2). Our obtained data are in a good agreement with the results of earlier dielectric and neutron diffraction measurements.
Abstract The structure and dielectric properties of sodium nitrite and its solid solutions confined in porous glasses have been studied. The temperature dependences of the order parameter and the unit cell volume for NaNO2 embedded into... more
Abstract The structure and dielectric properties of sodium nitrite and its solid solutions confined in porous glasses have been studied. The temperature dependences of the order parameter and the unit cell volume for NaNO2 embedded into porous glasses with different pore ...
Peculiarities of phase transitions in disordered perovskite-like crystals—PbMg1/3 Nb2/3 O3 (PMN) and Na1/2 Bi1/2 TiO3 (NBT) have been studied by neutron scattering. The strong quasielastic scattering (QES) related to ferroelectric... more
Peculiarities of phase transitions in disordered perovskite-like crystals—PbMg1/3 Nb2/3 O3 (PMN) and Na1/2 Bi1/2 TiO3 (NBT) have been studied by neutron scattering. The strong quasielastic scattering (QES) related to ferroelectric critical fluctuations has been observed instead of expected inelastic scattering of soft phonon mode. The wavevector dependence of this diffuse scattering has been well described by Ornstein-Zernice formula. The correlation
We measured the time dependencies of the dielectric permittivity of a single crystal lead magnoniobate in the zero-fieldcooled regime. The logarithmic decay of the dielectric response was observed in the glassy phase. We measured the... more
We measured the time dependencies of the dielectric permittivity of a single crystal lead magnoniobate in the zero-fieldcooled regime. The logarithmic decay of the dielectric response was observed in the glassy phase. We measured the time τ from the moment of the field application for ...
ABSTRACT (1-x)PbMg1/3Nb2/3O3-xPbTiO3 (PMN-PT) single crystals of different compositions were studied via piezoresponse force microscopy (PFM). Piezoelectric contrast has been observed in 0.9PMN-0.1PT above the temperature of structural... more
ABSTRACT (1-x)PbMg1/3Nb2/3O3-xPbTiO3 (PMN-PT) single crystals of different compositions were studied via piezoresponse force microscopy (PFM). Piezoelectric contrast has been observed in 0.9PMN-0.1PT above the temperature of structural transition indicating spatial distribution of polarization and was attributed to the existence of polar clusters. The domain patterns were found to change drastically with increasing Ti content. In particular, the piezoresponse images of 0.8PMN-0.2PT combine both relaxor and ferroelectric features and in 0.65PMN-0.35PT crystals only micron-sized ferroelectric domains were observed. The evolution of the polar structures with increasing temperature and under external electric field was also investigated. The nature of the observed phenomena is discussed based on the current understanding of the relaxor state in ferroelectrics and possible influence of PFM instrumentation
Diffuse neutron scattering in relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 . Sergey Vakhrusheva, Alexandre Ivanov*b and Jiri Kuldab. a Ioffe Physico-Technical Institute, 26, Politekhnicheskaya, 194021, St.-Petersburg, Russia. ... 11, PN... more
Diffuse neutron scattering in relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 . Sergey Vakhrusheva, Alexandre Ivanov*b and Jiri Kuldab. a Ioffe Physico-Technical Institute, 26, Politekhnicheskaya, 194021, St.-Petersburg, Russia. ... 11, PN Timonin, Ferroelectrics, 1997, 199, 67 . ...
The origin of relaxor ferroelectric behavior is complex, and is likely to include both compositional as well as structural order and disorder. Non-crystallographic methods of structural study by pulsed neutron and synchrotron X-ray... more
The origin of relaxor ferroelectric behavior is complex, and is likely to include both compositional as well as structural order and disorder. Non-crystallographic methods of structural study by pulsed neutron and synchrotron X-ray scattering applied to these solids reveal mas-sive local displacive disorder and short range compositional order in these solids. Examples of such local structural complexities in PMN and
ABSTRACT A detailed lattice-dynamic investigation on the relaxor ferroelectric PMN was started to search for "additional" modes (dispersion curves). But the results are complex with 4 branches observed below 6.5 THz, a... more
ABSTRACT A detailed lattice-dynamic investigation on the relaxor ferroelectric PMN was started to search for "additional" modes (dispersion curves). But the results are complex with 4 branches observed below 6.5 THz, a broad unresolved continuum between 6.5 and 12 THz, a well defined excitation at 13.4 THz with longitudinal and transverse character and further weak signals above 16 THz. Possible effects caused by disorder are discussed.
ABSTRACT Preliminary results of lattice-dynamical shell-model calculations for the relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) in the virtual-ion approximation are presented. The model parameters are fitted to Raman scattering and... more
ABSTRACT Preliminary results of lattice-dynamical shell-model calculations for the relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) in the virtual-ion approximation are presented. The model parameters are fitted to Raman scattering and low-frequency inelastic neutron scattering data, and higher-frequency dispersion curves are predicted.
The temperature evolution of the crystal structure of KD 2 PO 4 (DKDP) embedded in a porous glass with 7 nm pore diameter has been studied by neutron diffraction in temperature interval 90 K-308 K. It is shown that confined DKDP forms... more
The temperature evolution of the crystal structure of KD 2 PO 4 (DKDP) embedded in a porous glass with 7 nm pore diameter has been studied by neutron diffraction in temperature interval 90 K-308 K. It is shown that confined DKDP forms interconnected clusters with characteristic size of 18(0.5) nm. The structure of this nanocomposite material is found to be
Abstract New X-ray and neutron diffraction results for simple perovskites PbTiO3, BaTiO3 and complexes PbxBa1-xSc1/2Nb1/2O3 are presented. The static or dynamic disordered shifts and anharmonic thermal motions of the different atoms are... more
Abstract New X-ray and neutron diffraction results for simple perovskites PbTiO3, BaTiO3 and complexes PbxBa1-xSc1/2Nb1/2O3 are presented. The static or dynamic disordered shifts and anharmonic thermal motions of the different atoms are compared and discussed in connection with the dielectric properties and the existence of structural phase transitions.
