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Structure development and dielectric properties of Zn-doped Pb([Mg,Fe],W)O <sub/>3</sub> perovskite ceramics
摘要： Ceramic samples of a pseudo-binary system Pb(Mg1/2W1/2)O3-Pb(Fe2/3W1/3)O3 (PMW-PFW) were prepared by solid-state reaction. In addition, their compositions were modified by 20 mol% Pb(Zn1/2W1/2)O3 (PZW) doping in order to investigate the role of zinc in the perovskite formation and dielectric properties. The perovskite contents were ≥95.1% at the overall composition range, except for a significantly low value of 79.0% at 0.8PFW-0.2PZW. The extension of sintering time for PMW accelerated superstructure formation, resulting in the ordering factor increased up to 0.40 after 12 h heat treatment. The maximum dielectric constant values increased with increasing PFW fractions. In comparison, the phase transition temperatures decreased sharply (by up to 161 ℃) at low concentrations of PFW, followed by mild changes (by up to 47 ℃) afterwards. The dielectric constant spectra were analyzed in terms of diffuseness characteristics, which reflected the phase transition modes quite well.
关键词： dielectric materials/properties,perovskites,ferroelectricity/ferroelectric materials,reaction
更新于2025-09-09 09:28:46
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Electron-phonon anharmonicity and low thermal conductivity in phosphorous chalcogenide ferroelectrics
摘要： The dependence of thermal conductivity with temperature has been studied for Sn(Pb)2P2S(Se)6 ferroelectrics-semiconductors, showing an ultra-low (0.5 W/m K) thermal conductivity above 250 K and the possibility to tune it at lower temperatures playing with the dopant concentration. This behavior has been explained taking into account the combination of different physical mechanisms: hopping heat conductivity in a lattice with strong electron-phonon anharmonicity linked to the stereoactivity of tin and lead cations electron lone pairs together with valence fluctuations in P2S(Se)6 groups. Besides, the presence of an incommensurate phase in the more covalent compounds, the location of tricritical points near 250 K and the peculiarities of the chemical bonding have all been correlated with the experimental behavior observed.
关键词： Ferroelectricity,Bonding,Thermal Conductivity,Structure–Property Relationship,Temperature Dependence
更新于2025-09-09 09:28:46
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Room temperature multiferroic properties of Fe-doped nonstoichiometric SrTiO3 ceramics at both A and B sites
摘要： This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted nonstoichiometric STO ceramics. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The room temperature multiferroicity of the Fe-doped Ti-rich STO ceramics is successfully realized by M-H hysteresis loop, P-E hysteresis loop and magnetodielectric measurement. The origins of ferroelectricity may be related to the lattice distortions and antisite-like defects with net local dipoles. The ferromagnetism are mainly contributed by the competitions among the double exchange interactions, super-exchange interactions and the non-linear ferromagnetic exchange coupling. In addition, the ordered spin arrangement of the ferromagnetism is formed by the exchange interaction of Fe atom using first principle simulations.
关键词： D. Ferromagnetism,A. Perovskite,E. Solid-state reactions,D. Ferroelectricity
更新于2025-09-09 09:28:46
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Three-dimensional atomic scale electron density reconstruction of octahedral tilt epitaxy in functional perovskites
摘要： Octahedral tilts are the most ubiquitous distortions in perovskite-related structures that can dramatically influence ferroelectric, magnetic, and electronic properties; yet the paradigm of tilt epitaxy in thin films is barely explored. Non-destructively characterizing such epitaxy in three-dimensions for low symmetry complex tilt systems composed of light anions is a formidable challenge. Here we demonstrate that the interfacial tilt epitaxy can transform ultrathin calcium titanate, a non-polar earth-abundant mineral, into high-temperature polar oxides that last above 900 K. The comprehensive picture of octahedral tilts and polar distortions is revealed by reconstructing the three-dimensional electron density maps across film-substrate interfaces with atomic resolution using coherent Bragg rod analysis. The results are complemented with aberration-corrected transmission electron microscopy, film superstructure reflections, and are in excellent agreement with density functional theory. The study could serve as a broader template for non-destructive, three-dimensional atomic resolution probing of complex low symmetry functional interfaces.
关键词： tilt epitaxy,ferroelectricity,Octahedral tilts,coherent Bragg rod analysis,perovskite
更新于2025-09-09 09:28:46
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The Origin of Two-Dimensional Vertical Ferroelectricity in WTe <sub/>2</sub> Bilayer and Multilayer
摘要： In a recent report, room-temperature vertical ferroelectricity was experimentally shown in WTe2 bilayer, while its mechanism of ferroelectric switching without vertical ion displacements remains unclarified. In this work we reveal its origin by first-principles calculations that the polarization stems from uncompensated interlayer vertical charge transfer depending on in-plane translation, which can be switched upon interlayer sliding. The calculated results are consistent with experimental data, and similar switching mechanism can be applied to multilayer counterpart. Despite its small ferroelectric switching barrier and polarization, the in-plane rigidity of WTe2 layer gives rise to a high Curie temperature. A Moire pattern of ferroelectric domain superlattice can be formed and tuned upon a small-angle twist of bilayer, which is unique compared with traditional ferroelectrics. Similar interlayer translational ferroelectricity may exist in a series of van der Waals bilayers or even bulk phases.
关键词： Two-dimensional,WTe2,First-principles calculations,Ferroelectricity,Interlayer sliding
更新于2025-09-04 15:30:14