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Yu-Qing Zhao, Qi-Rui Ma, Biao Liu, Zhuo-Liang Yu, Meng-Qiu Cai
Ab initio simulations combined with the Berry phase method are employed to investigate ferroelectric polarization of tetragonal CsPbBr3 crystals by applying hydrostatic pressure varying from 0 to 19 GPa; we find that the object research belongs to the P4mm space group. The calculated results show that the materials undergo a paraelectric-ferroelectric phase transition when the pressure increases to a critical value 15 GPa. The polarization is strongly enhanced and attains a high value of about 23 μC cm-2, owing to the increase in the ionic and electric contributions to the polarization under compressive strain...
May 18, 2018: Physical Chemistry Chemical Physics: PCCP
Lina Li, Xiaoying Shang, Sasa Wang, Ningning Dong, Chengmin Ji, Xueyuan Chen, Sangen Zhao, Jun Wang, Zhihua Sun, Maochun Hong, Junhua Luo
Perovskite ferroelectrics with prominent nonlinear optical absorption have attracted great attention in the field of photonics. However, they are traditionally dominated by inorganic oxides and exhibit relatively small nonlinear optical absorption coefficients which hinder their further applications. Herein, we report a new organic-inorganic hybrid bilayered perovskite ferroelectric, (C4H9NH3)2(NH2CHNH2)Pb2Br7 (1), showing an above-room-temperature Curie temperature (~322 K) and notable spontaneous polarization (~3...
May 17, 2018: Journal of the American Chemical Society
Floriana Craciun, Francesco Cordero, Bogdan S Vasile, Victor Fruth, Maria Zaharescu, Irina Atkinson, Roxana Trusca, Lucian Diamandescu, Liviu C Tanase, Pietro Galizia, Marin Cernea, Carmen Galassi
The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O3 (x = 0.00, 0.03, 0.04, 0...
May 17, 2018: Physical Chemistry Chemical Physics: PCCP
Yanan Wang, Hongli Guo, Qijing Zheng, Wissam A Saidi, Jin Zhao
Solvated electron states at oxide/aqueous interface represent the lowest energy charge transfer pathways, thereby playing an important role in photocatalysis and electronic device applications. However, their energies are usually higher than the conduction band minimum (CBM), which makes the solvated electrons difficult to utilize in charge transfer processes. Thus, it is essential to stabilize the energy of the solvated electron states. In this report, taking LaAlO3/SrTiO3 (LAO/STO) oxide heterostructure with H2O adsorbed monolayer as a prototypical system, we show using DFT and ab initio time dependent nonadiabatic molecular dynamics simulation that the energy and dynamics of solvated electrons can be tuned by the electric field in the polar-nonpolar oxide heterostructure...
May 16, 2018: Journal of Physical Chemistry Letters
Anatoly Kaznacheev, Evgeny Pozhidaev, Vladimir Rudyak, Alexander V Emelyanenko, Alexei Khokhlov
A biaxial surface potential Φ_{s} of smectic-C^{*} surface-stabilized ferroelectric liquid crystals (SSFLCs) is introduced in this paper to explain the experimentally observed electric-field dependence of polarization P[over ̃]_{cell}(E), in particular the shape of the static hysteresis loops. Our potential consists of three independent parts. The first nonpolar part Φ_{n} describes the deviation of the prime director n (which is the most probable orientation of the long molecular axes) from the easy alignment axis R, which is located in the boundary surface plane...
April 2018: Physical Review. E
Nikita V Solodkov, Mamatha Nagaraj, J Cliff Jones
Tilted smectic liquid crystal phases such as the smectic-C phase seen in calamitic liquid crystals are usually treated using the assumption of biaxial orthorhombic symmetry. However, the smectic-C phase has monoclinic symmetry, thereby allowing disassociation of the principal optic and dielectric axes based on symmetry and invariance principles. This is demonstrated here by comparing optical and dielectric measurements for two materials with highly first-order direct transitions from nematic to smectic-C phases...
April 2018: Physical Review. E
M Paściak, T R Welberry, J Kulda, S Leoni, J Hlinka
The three-dimensional distribution of the x-ray diffuse scattering intensity of BaTiO_{3} has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO_{3} to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material...
April 20, 2018: Physical Review Letters
Andrés Concha, David Aguayo, Paula Mellado
Materials that have hysteretic response to an external field are essential in modern information storage and processing technologies. A myriad of magnetization curves of several natural and artificial materials have previously been measured and each has found a particular mechanism that accounts for it. However, a phenomenological model that captures all the hysteresis loops and at the same time provides a simple way to design the magnetic response of a material while remaining minimal is missing. Here, we propose and experimentally demonstrate an elementary method to engineer hysteresis loops in metamaterials built out of dipolar chains...
April 13, 2018: Physical Review Letters
Matej Sadl, Andraz Bradesko, Darko Belavic, Andreja Bencan, Barbara Malic, Tadej Rojac
Piezoelectric ceramic resonant pressure sensors have shown potential as sensing elements for harsh environments, such as elevated temperatures. For operating temperatures exceeding ~250 °C, conventional and widely used Pb(Zr,Ti)O₃ (PZT) piezoelectrics should be replaced. Here, a ceramic pressure sensor from low-temperature co-fired ceramics (LTCC) was constructed by integrating a piezoelectric actuator made from bismuth ferrite (BiFeO₃) on a diaphragm. This ferroelectric material was selected because of its high Curie temperature (TC = 825 °C) and as a lead-free piezoelectric extensively investigated for high-temperature applications...
May 3, 2018: Sensors
Zhenyue Wu, Chengmin Ji, Lina Li, Jintao Kong, Zhihua Sun, Sangen Zhao, Sasa Wang, Maochun Hong, Junhua Luo
Cesium-lead halide perovskites (e.g. CsPbBr3) have gained widespread attentions due to their rich physical attributes, whereas bulk ferroelectricity remains still unexplored in this system. Here, by alloying the flexible organic cation into the cubic prototype of CsPbBr3, we successfully design the first cesium-based two-dimensional (2D) perovskite ferroelectric with both inorganic alkali metal and organic cations, (C4H9NH3)2CsPb2Br7 (1). Strikingly, 1 shows a high Curie temperature (Tc = 412 K) beyond that of BaTiO3 (~393 K) and notable spontaneous polarization (~4...
May 11, 2018: Angewandte Chemie
Lauren M Garten, Shyam Dwaraknath, Julian Walker, John S Mangum, Paul F Ndione, Yoonsang Park, Daniel A Beaton, Venkatraman Gopalan, Brian P Gorman, Laura T Schelhas, Michael F Toney, Susan Trolier-McKinstry, Kristin A Persson, David S Ginley
Many technologically critical materials are metastable under ambient conditions, yet the understanding of how to rationally design and guide the synthesis of these materials is limited. This work presents an integrated approach that targets a metastable lead-free piezoelectric polymorph of SrHfO3 . First-principles calculations predict that the previous experimentally unrealized, metastable P4mm phase of SrHfO3 should exhibit a direct piezoelectric response (d33 ) of 36.9 pC N-1 (compared to d33 = 0 for the ground state)...
May 10, 2018: Advanced Materials
Hao Pan, Jing Ma, Ji Ma, Qinghua Zhang, Xiaozhi Liu, Bo Guan, Lin Gu, Xin Zhang, Yu-Jun Zhang, Liangliang Li, Yang Shen, Yuan-Hua Lin, Ce-Wen Nan
Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm-3 , together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering...
May 8, 2018: Nature Communications
Lu Zheng, Hui Dong, Xiaoyu Wu, Yen-Lin Huang, Wenbo Wang, Weida Wu, Zheng Wang, Keji Lai
The electrical generation and detection of elastic waves are the foundation for acoustoelectronic and acoustooptic systems. For surface acoustic wave devices, microelectromechanical/nanoelectromechanical systems, and phononic crystals, tailoring the spatial variation of material properties such as piezoelectric and elastic tensors may bring significant improvements to the system performance. Due to the much slower speed of sound than speed of light in solids, it is desirable to study various electroacoustic behaviors at the mesoscopic length scale...
May 7, 2018: Proceedings of the National Academy of Sciences of the United States of America
Mengwei Si, Chunsheng Jiang, Wonil Chung, Yuchen Du, Muhammad Ashraf Alam, Peide D Ye
P-type 2-dimensional steep-slope negative capacitance field-effect transistors are demonstrated for the first time, with WSe2 as channel material and ferroelectric hafnium zirconium oxide in gate dielectric stack. F4-TCNQ is used as p-type dopant to suppress electron leakage current and to reduce Schottky barrier width for holes. WSe2 negative capacitance field-effect transistors with and without internal metal gate structures and the internal field-effect transistors are compared and studied. Significant SS reduction is observed in WSe2 negative capacitance field-effect transistors by inserting the ferroelectric hafnium zirconium oxide layer, suggesting the existence of internal amplification (~10) due to the negative capacitance effect...
May 7, 2018: Nano Letters
Robert R Benoit, Delaney M Jordan, Gabriel L Smith, Ronald G Polcawich, Sarah S Bedair, Daniel M Potrepka
Direct-write laser grayscale lithography has been used to facilitate a single-step patterning technique for multilayer lead zirconate titanate (PZT) thin films. A 2.55- -thick photoresist was patterned with a direct-write laser. The intensity of the laser was varied to create both tiered and sloped structures that are subsequently transferred into multilayer PZT(52/48) stacks using a single Ar ion-mill etch. Traditional processing requires a separate photolithography step and an ion mill etch for each layer of the substrate, which can be costly and time consuming...
May 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Jingfeng Song, Zhiyong Xiao, Bo Chen, Spencer Prockish, Xuegang Chen, Anil Rajapitamahuni, Le Zhang, Jinsong Huang, Xia Hong
We report a more than 10-fold enhancement of the piezoelectric coefficient d33 of polycrystalline CH3NH3PbI3 (MAPbI3) films when interfacing them with ferroelectric PbZr0.2Ti0.8O3 (PZT). Piezo-response force microscopy (PFM) studies reveal d_33^(MAPbI_3 ) values of ~0.3 pm/V for MAPbI3 deposited on Au, ITO and SrTiO3 surfaces, with small phase angle fluctuating at length scales smaller than the grain size. In sharp contrast, on samples prepared on epitaxial PZT films, we observe large scale polar domains exhibiting clear, close to 180° PFM phase contrasts, pointing to polar axes along the film normal...
May 7, 2018: ACS Applied Materials & Interfaces
Marlena Gryl, Tomasz Seidler, Joanna Wojnarska, Katarzyna Marta Stadnicka, Irena Matulková, Ivan Němec, Petr Němec
Technological innovation enforces a revolutionized approach towards materials chemistry. In this manuscript a new methodology towards crystal engineering of polar materials for possible applications in linear or non-linear optics, as ferroelectric, pyroelectric or piezoelectric crystals has been presented. The necessity to fulfil several criteria concerning symmetry, electron properties of the building blocks and also mechanical and optical stability was achieved by fusion of pharmaceutical molecule and NLO-phore...
May 7, 2018: Chemistry: a European Journal
Rui Wu, Ahmed Kursumovic, Xingyao Gao, Chao Yun, Mary E Vickers, Haiyan Wang, Seungho Cho, Judith L MacManus-Driscoll
Electric field control of magnetism is a critical future technology for low-power, ultrahigh density memory. However, despite intensive research efforts, no practical material systems have emerged. Interface-coupled, composite systems containing ferroelectric and ferri-/ferromagnetic elements have been widely explored, but they have a range of problems, for example, substrate clamping, large leakage, and inability to miniaturize. In this work, through careful material selection, design, and nanoengineering, a high-performance room-temperature magnetoelectric system is demonstrated...
May 18, 2018: ACS Applied Materials & Interfaces
Bolin Tang, Bo Zhang, Junjun Zhuang, Qi Wang, Lingqing Dong, Kui Cheng, Wenjian Weng
Surface potential of biomaterials can dramatically influence cellular osteogenic differentiation. In this work, a wide range of surface potential on ferroelectric polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) films was designed to get insight into the interfacial interaction of cell-charged surface. The P(VDF-TrFE) films poled by contact electric poling at various electric fields obtained well stabilized surface potential, with wide range from -3 to 915 mV. The osteogenic differentiation level of cells cultured on the films was strongly dependent on surface potential and reached the optimum at 391 mV in this system...
May 2, 2018: Acta Biomaterialia
Jun-Hui Lei, Yu-Qing Zhao, Qiong Tang, Jian-Guo Lin, Meng-Qiu Cai
Organic-inorganic hybrid perovskites are developed to pursue high charge carrier mobility and light absorption coefficient. In this study, we present a detailed comparative research of the atomic and electronic structures of single-layered perovskites (C4H9NH3)2PbBr4 with two-dimensional/three-dimensional (2D/3D) spatial arrangement to predict the in plane charge carrier mobility along with the charge effective mass, elastic constant, and deformation potential. The calculated results reveal that the intrinsic in plane carrier mobilities of 2D single-layered hybrid perovskite (C4H9NH3)2PbBr4 along the 100 and 010 directions are superior to those of the 3D structure...
May 4, 2018: Physical Chemistry Chemical Physics: PCCP
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