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We have studied a dense domain structure (DDS) appearing during polarization reversal in rhombohedral (111)-cut lead magnesium niobate-lead titanate single crystals. The complicated shape of the switching current was explained by means of non-uniform motion of the boundary between the DDS and c-domains using comparative analysis of the optical current and kinetic map. 2D-vector piezoresponse force microscopy revealed that DDS represented needle-like a-domains inside the a-domains with different vertical orientations of spontaneous polarization. © 2020 Author(s). The equipment of the Ural Center for Shared Use “Modern Nanotechnology” UrFU was used. This work has been supported in part by the Ministry of Science and Higher Education of the Russian Federation under Project No. 3.9534.2017/8.9, by the Government of the Russian Federation (Act 211, Agreement No. 02.180 A03.21.0006) and by RFBR (Grant No. 17-52-80116-BRICS_a). This work was supported by the NSFC projects (Grant No. 51761145024), Shaan Xi province Project (Nos. 2017 ktpt-21 and 2018TD-024), and the 111 Project under Grant No. B14040.

Potential ferroelectricity in charge-transfer organic materials is often masked by the intrinsic conductivity. Here, we report the compelling evidence of ferroelectricity in organic p-conjugated meta-nitroaniline (m-NA) crystals as shown by the local electromechanical measurements using the piezoresponse force microscopy (PFM) technique. m-NA is a charge-transfer molecular material with the exceptional optical non-linearity and perceptible conductivity along the crystallographic polar axis. While standard Sawyer-Tower measurements revealed an apparently lossydielectric hysteresis, The PFM switching spectroscopy indicated clear ferroelectric behaviour in this technologically important multifunctional material. Further study of the pyroelectric properties in m-NA crystals confirmed their high spontaneous polarization of 18 microC/cm2 at room temperature, comparable to the best known organic ferroelectrics., This work was supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124FEDER-014628, FCOMP-01-0124-FEDER-009457)and FCT Grant No. PTDC/CTMNAN/114269/2009), Pest-C/CTM/ LA0011/013, and by RFBR Grant No. 13-02-90925. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (POCI-01-0145FEDER-007679, FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement, and by Government of the RF (Act 211, Agreement 02.A03.21.0006).

The lead zirconate titanate (PZT) ferroelectric ceramics was sintered using microwave sintering and conventional sintering technique, respectively. The formation of single phase was confirmed by X-ray diffraction. It has been observed that the microwave sintered PZT ceramics show better densification, fine and uniform grain size, higher dielectric constant and improved piezoelectric coefficient constant d33. The dielectric properties were studied as a function of frequency and temperature. This promising technique has distinguished characteristics of energy-saving, rapid processing and uniform temperature distribution throughout the sample. The values of remnant polarization, Pr, and spontaneous polarization, P s, are slightly higher for microwave sintered sample. The value of Ec in the microwave sintered sample is low and this property was desirable for device fabrication of PZT-based smart structures. � 2010 Elsevier B.V. All rights reserved.

A combination of mechanical alloying and spark plasma sintering (SPS) was used to process Ba0.9Sr0.1TiO3 (abbreviated as BST) with a high-density and homogeneous microstructure, at a temperature 300�C to 400�C lower than that used in conventional sintering. The SPS technique was employed to prepare dense Ba0.9Sr0.1TiO3 nano-ceramics at different temperatures ranging from 800�C to 1000�C within a very short time. The SPS samples were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrical, ferroelectric and piezoelectric property measurements. The dielectric constant both at room temperature and Curie temperature increased with increasing SPS temperature. The coercive field increased continuously with rising SPS temperature, but the spontaneous polarization increased gradually up to 900�C and then decreased considerably with further increases in SPS temperature. In addition, the prepared nano-ceramic exhibited excellent piezoelectric properties. � 2015, The Minerals, Metals & Materials Society.

We consider a typical heterostructure "domain patterned ferroelectric film - ultra-thin dielectric layer - semiconductor," where the semiconductor can be an electrolyte, paraelectric or multi-layered graphene. Unexpectedly, we have found that the space charge modulation profile and amplitude in the semiconductor, that screens the spontaneous polarization of a 180-deg domain structure of ferroelectric, depends on the domain structure period, dielectric layer thickness and semiconductor screening radius in a rather non-trivial nonlinear way. Multiple size effects appearance and manifestation are defined by the relationship between these three parameters. In addition, we show that the concept of effective gap can be introduced in a simple way only for a single-domain limit. Obtained analytical results open the way for understanding of current-AFM maps of contaminated ferroelectric surfaces in ambient atmosphere as well as explore the possibilities of conductivity control in ultra-thin semiconductor layers. © 2014 AIP Publishing LLC.

The barium lead titanate (Ba0.8Pb0.2TiO3, termed BPT) ferroelectric ceramics were prepared using microwave sintering and spark plasma sintering (SPS) techniques. The formation of single phase was confirmed by X-ray diffraction. The SPS-prepared BPT ceramics exhibited higher density and smaller grain sizes as compared with the microwave-sintered ones. Dielectric and ferroelectric properties were compared between the two-technique-prepared ceramics. It was found that the dielectric constant at room temperature was ?500 higher for the SPS-prepared sample than for the microwave-sintered one, and ?6000 higher at Curie transition temperature. The remnant and spontaneous polarization values were ?2 times larger for the SPS-prepared sample as compared with the microwave-sintered one. On the whole, the promising SPS technique possessed distinguished characteristics of energy-saving, rapid processing and uniform temperature distribution throughout the sample. � 2013 Elsevier B.V. All rights reserved.

The nanocrystalline ferroelectric LiNbO3 films on (001) Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown using the ion beam sputtering method. The remanent polarization and the coercive field are 12 μC/cm2 and 29 kV/cm, respectively. The thermal annealing leads to the coarsening of the grains. The appearance of the "local texture," which gives rise to the unipolarity of the heterostructures caused by the predominance of the one direction in the vertical component of the spontaneous polarization, is investigated. © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.

We report the effect of a thin GaN (2 nm) interlayer on the magnetotransport properties of AlInN/AlN/GaN-based heterostructures. Two samples were prepared (Sample A: AlInN/AlN/GaN and sample B: AlInN/GaN/AlN/GaN). Van der Pauw and Hall measurements were performed in the 1.9-300 K temperature range. While the Hall mobilities were similar at room temperature (RT), sample B had nearly twice as large Hall mobility as sample A at the lowest temperature; 679 and 889 cm 2/Vs at RT and 1460 and 3082 cm 2/Vs at 1.9 K for samples A and B. At 1.9-10 K, the longitudinal magnetoresistance was measured up to 9 T, in turn revealing Shubnikov-de Haas (SdH) oscillations. The carrier concentration, effective mass and quantum mobility of the two-dimensional electron gas (2DEG) were determined from SdH oscillations. At 1.9 K, the 2DEG concentration of sample B was nearly seven times larger than of sample A (1.67 × 10 13/cm 2 vs. 0.24 × 10 13/cm 2). On the contrary, the quantum mobility was changed adversely nearly three times (sample B 2500 cm 2/Vs and sample A 970 cm 2/Vs). The increase of the 2DEG concentration was attributed to the existence of the GaN interlayer, which has strengthened the spontaneous polarization difference between the AlInN and GaN layers of the heterostructure. Hence, the stronger electric field at the 2DEG region bent the conduction band profile downwards and consequently the quantum mobility decreased due to the increased interface roughness scattering. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrooptic and dielectric properties of ferroelectric liquid crystals/chiral carbon nanotubes dispersions were investigated. It was demonstrated that even a small amount of chiral single walled carbon nanotubes affects greatly the performance of ferroelectric liquid crystal cells. Particularly, the spontaneous polarization, the Goldstone mode dielectric strength and the rise time are decreased in doped cells. The experimental results are explained by two effects. First, the spontaneous polarization of the FLC is screened by the π-π electron system of the carbon nanotube. Secondly, π electrons trap the ionic impurities which results in significant modification of the internal electric field inside the cells. © 2009 Elsevier B.V. All rights reserved.

The sensitivity of spontaneous polarization to epitaxial strains is evaluated for several perovskite ferroelectrics using the nonlinear thermodynamic theory. For BaTiO3, PbTiO3, and Pb (Zr 0.2 Ti0.8) O3 epitaxial layers subjected to large compressive in-plane strains, the predicted relative polarization changes agree with the results of first-principles calculations. This agreement shows that the strain sensitivity of polarization is predominantly governed by the linear electrostriction even at large strains. The calculations performed for Pb (Zr1-x Tix) O3 films of different compositions further demonstrate that the strain sensitivity strongly enhances near the morphotropic phase boundary, breaking the inverse correlation with the bulk polarization that was proposed earlier. © 2008 American Institute of Physics.