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Sergey Vakhrushev

Bio: Sergey Vakhrushev is an academic researcher from Ioffe Institute. The author has contributed to research in topics: Ferroelectricity & Dielectric. The author has an hindex of 29, co-authored 108 publications receiving 2836 citations. Previous affiliations of Sergey Vakhrushev include Saint Petersburg State University & Saint Petersburg State Polytechnic University.


Papers
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TL;DR: In this article, the results of experimental studies of the crystal and domain structures of NaO, 5BiO and 5TiO3 as well as its lattice dynamics, dielectric, optical and other physical properties are considered.
Abstract: The results of experimental studies of the crystal and domain structures of NaO, 5BiO, 5TiO3 as well as its lattice dynamics, dielectric, optical and other physical properties are considered. Nature of peculiar temperature points is discussed.

245 citations

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TL;DR: It is shown that the dielectric permittivity of a single crystal lead magnoniobate in the zero- field zero-fieldcooled regime depends linearly on both the inverse temperature and the inverse applied field strength.
Abstract: We measured the time dependencies of the dielectric permittivity of a single crystal lead magnoniobate in the zero-field\char21{}cooled regime. The logarithmic decay of the dielectric response was observed in the glassy phase. We measured the time $\ensuremath{\tau}$ from the moment of the field application for the phase transition from the glasslike to the field-induced ferroelectric state to take place, at temperatures below 220 K. The transition is accompanied by the emerging of the even harmonics of the permittivity. It is shown that $\mathrm{ln}\ensuremath{\tau}$ depends linearly on both the inverse temperature and the inverse applied field strength.

228 citations

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TL;DR: This work reports the results of a study on the lattice dynamics of the antiferroelectric lead zirconate using inelastic and diffuse X-ray scattering techniques and the Brillouin light scattering, and suggests an approach to the treatment of complex phase transitions in ferroics.
Abstract: Antiferroelectrics are essential ingredients for the widely applied piezoelectric and ferroelectric materials: the most common ferroelectric, lead zirconate titanate is an alloy of the ferroelectric lead titanate and the antiferroelectric lead zirconate. Antiferroelectrics themselves are useful in large digital displacement transducers and energy-storage capacitors. Despite their technological importance, the reason why materials become antiferroelectric has remained allusive since their first discovery. Here we report the results of a study on the lattice dynamics of the antiferroelectric lead zirconate using inelastic and diffuse X-ray scattering techniques and the Brillouin light scattering. The analysis of the results reveals that the antiferroelectric state is a 'missed' incommensurate phase, and that the paraelectric to antiferroelectric phase transition is driven by the softening of a single lattice mode via flexoelectric coupling. These findings resolve the mystery of the origin of antiferroelectricity in lead zirconate and suggest an approach to the treatment of complex phase transitions in ferroics.

227 citations

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TL;DR: In this paper, the structural evolution of PMN/PT10% and PMN (PbMg 0. 3 Nb 0. 6 Ti 0. 1 O 3 ) was studied and compared using high-resolution x-ray and neutron diffraction.
Abstract: Structural evolutions of PMN/PT10% (PbMg 0 . 3 Nb 0 . 6 Ti 0 . 1 O 3 ) and PMN (PbMg 1 / 3 Nb 2 / 3 O 3 ) are studied and compared using high-resolution x-ray and neutron diffraction. At high temperature, PMN-like diffuse scattering, associated with local disordered shifts, is evidenced by PMN/PT10%. A part of this intensity condenses at T c =285 K when PMN/PT10% exhibits a structural phase transition toward a long-range rhombohedral phase, whereas in PMN the polar order remains short ranged. In the ferroelectric phase of PMN/PT10% local [100] displacements of lead are evidenced, and are connected to the observation of diffuse scattering far below T c . The local symmetry in which oxygen and Ti/Mg/Nb cations are shifted along the [111] direction, but in which the lead atoms are shifted along one of the tetragonal [100] directions is monoclinic. This short-range polar order reconstructs on average a polar rhombohedral symmetry. A global picture for the structural evolution in the PMN/PT compounds is proposed. It is based on competition between rhombohedral and tetragonal polar order, which connects the relaxation properties of PMN and the high piezoelectric response of morphotropic monoclinic PMN/PT with a high concentration of PT.

180 citations

Journal ArticleDOI
TL;DR: In this paper, the wavevector dependence of this diffuse scattering has been well described by Ornstein-Zernice formula and correlation length temperature dependence resembling that of spin-glasses has obtained.
Abstract: 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 length temperature dependence resembling that of spin-glasses has obtained. The history dependent effects have been found by measurements in electric field in “field cooled” (FC) and “zero field cooled” regimes. Those effects as well as long-time relaxation of Bragg peaks intensity, observed below certain temperature, clearly indicate glass-like nature of low-temperature phase.

111 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the lattice dynamics and the peculiar dielectric relaxation in relaxors are discussed, and theoretical models for the mechanisms of PNR formation and freezing into nonergodic glassy state are also presented.
Abstract: Relaxor ferroelectrics were discovered almost 50 years ago among the complex oxides with perovskite structure. In recent years this field of research has experienced a revival of interest. In this paper we review the progress achieved. We consider the crystal structure including quenched compositional disorder and polar nanoregions (PNR), the phase transitions including compositional order-disorder transition, transition to nonergodic (probably spherical cluster glass) state and to ferroelectric phase. We discuss the lattice dynamics and the peculiar (especially dielectric) relaxation in relaxors. Modern theoretical models for the mechanisms of PNR formation and freezing into nonergodic glassy state are also presented.

1,784 citations

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TL;DR: In this article, a figure of merit analysis for key devices is presented and used to contrast lead-containing and lead-free piezoceramics for demanding applications with high reliability, displacements and frequency as well as a wide temperature range.
Abstract: After twenty years of partly quiet and ten years of partly enthusiastic research into lead-free piezoceramics there are now clear prospects for transfer into applications in some areas. This mimics prior research into eliminating lead from other technologies that resulted in restricted lead use in batteries and dwindling use in other applications. A figure of merit analysis for key devices is presented and used to contrast lead-containing and lead-free piezoceramics. A number of existing applications emerge, where the usage of lead-free piezoceramics may be envisaged in the near future. A sufficient transition period to ensure reliability, however, is required. The use of lead-free piezoceramics for demanding applications with high reliability, displacements and frequency as well as a wide temperature range appears to remain in the distant future. New devices are outlined, where the figure of merit suggests skipping lead-containing piezoceramics altogether. Suggestions for the next pertinent research requirements are provided.

966 citations

Journal ArticleDOI
TL;DR: In this paper, the impact factors on the hysteresis loops are discussed based on recent developments in ferroelectric and related materials, including the effect of materials (grain size and grain boundary, phase and phase boundary, doping, anisotropy, thickness), aging, and measurement conditions (applied field amplitude, fatigue, frequency, temperature, stress), which can affect the hysteretic behaviors of the ferroelectrics.
Abstract: Due to the nature of domains, ferroics, including ferromagnetic, ferroelectric, and ferroelastic materials, exhibit hysteresis phenomena with respect to external driving fields (magnetic field, electric field, or stress). In principle, every ferroic material has its own hysteresis loop, like a fingerprint, which contains information related to its properties and structures. For ferroelectrics, many characteristic parameters, such as coercive field, spontaneous, and remnant polarizations can be directly extracted from the hysteresis loops. Furthermore, many impact factors, including the effect of materials (grain size and grain boundary, phase and phase boundary, doping, anisotropy, thickness), aging (with and without poling), and measurement conditions (applied field amplitude, fatigue, frequency, temperature, stress), can affect the hysteretic behaviors of the ferroelectrics. In this feature article, we will first give the background of the ferroic materials and multiferroics, with an emphasis on ferroelectrics. Then it is followed by an introduction of the characterizing techniques for the loops, including the polarization–electric field loops and strain–electric field curves. A caution is made to avoid misinterpretation of the loops due to the existence of conductivity. Based on their morphologic features, the hysteresis loops are categorized to four groups and the corresponding material usages are introduced. The impact factors on the hysteresis loops are discussed based on recent developments in ferroelectric and related materials. It is suggested that decoding the fingerprint of loops in ferroelectrics is feasible and the comprehension of the material properties and structures through the hysteresis loops is established.

869 citations

Journal ArticleDOI
TL;DR: In this paper, the phase transition from the high-temperature prototypic cubic structure to one of tetragonal (673-773) and then rhombohedral structures (5-528) has been established.
Abstract: Rietveld neutron powder profile analysis of the compound Na0.5Bi0.5TiO3 (NBT) is reported over the temperature range 5–873 K. The sequence of phase transitions from the high-temperature prototypic cubic structure (above 813 K), to one of tetragonal (673–773 K) and then rhombohedral structures (5–528 K) has been established. Coexisting tetragonal/cubic (773–813 K) and rhombohedral/tetragonal (with an upper temperature limit of 145 K between 528 and 673 K) phases have also been observed. Refinements have revealed that the rhombohedral phase, space group R3c, with aH = 5.4887 (2), cH = 13.5048 (8) A, V = 352.33 (3) A3, Z = 6 and Dx = 5.99 Mg m−3, exhibits an antiphase, a−a−a− oxygen tilt system, ω = 8.24 (4)°, with parallel cation displacements at room temperature. The tetragonal phase, space group P4bm, with aT = 5.5179 (2), cT = 3.9073 (2) A, V = 118.96 (1) A3, Z = 2 and Dx = 5.91 Mg m−3, possesses an unusual combination of in-phase, a0a0c+ oxygen octahedra tilts, ω = 3.06 (2)°, and antiparallel cation displacements along the polar axis. General trends of cation displacements and the various deviations of the octahedral network from the prototypic cubic perovskite structure have been established and their systematic behaviour with temperature is reported. An investigation of phase transition behaviour using second harmonic generation (SHG) to establish the centrosymmetric or non-centrosymmetric nature of the various phases is also reported.

799 citations