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Using first-principles calculations, we designed a two-dimensional material, monolayer AgBiPSe, with the thickness of only 6 Å, which exhibited out-plane ferroelectricity. The ground state of the monolayer AgBiPSe was not purely ferroelectric since the out-plane ferroelectricity originated from the compensated ferrielectric state: the off-centering antiparallel displacements of Ag and Bi ions. The compensated ferrielectric ordering has superiority on reducing the depolarization field to stabilize the ferroelectricity. Furthermore, together with strong visible-light adsorption and suitable band edge alignments, we proposed the monolayer AgBiPSe as a visible-light photocatalyst for water-splitting as the out-plane polarization could enhance the electron-hole separation. Our results offer a new way to overcome the critical thickness limitation of nanoscale ferroelectrics. The out-plane ferroelectricity in monolayer AgBiPSe has great potential for developing various devices with desirable applications.

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On the basis of first-principles density functional calculations, we predict that Li-decorated graphyne can serve as a promising candidate for hydrogen storage, with a largest storage capacity of 18.6 wt %. The average adsorption energy of hydrogen is about −0.27 eV/H 2 , indicating that the doped system is an ideal hydrogen storage material at ambient conditions. It is proposed that the polarization mechanism, which stems from the electric field induced by the ionic Li coated on the graphyne, plays a key role in the adsorption of H 2 molecules. Furthermore, the formation of the hydrogen−hydrogen complex also stabilizes the adopted hydrogen molecules.

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A lead-free piezoelectric material with ultra-high properties, Ba(Ti0.8Zr0.2)O3-x(Ba0.7Ca0.3)TiO3(BZTxBCT) nanocrystals was synthesized via a sol-gel method, and the corresponding thin films were also deposited on Pt/Ti/SiO2/Si substrates by a spin-coating approach. The BZT-xBCT thin film exhibited a high remnant polarization of 22.15 mC cm2 with a large coercive field of 68.06 kV cm1. The resultant gel is calcined at various elevated temperatures and studied with FTIR/XRD/Raman/DSC-TGA/AFM/SEM techniques for gel composition, crystallization, phase transition, thermochemistry and the morphology of the film. Although the room temperature crystal structure of the BZT-xBCT nanocrystals appears to be a standard perovskite structure by conventional X-ray diffraction (XRD), Raman spectroscopy demonstrates the presence of non-centrosymmetric regions arising from the off-centering of the titanium (zirconium) atoms.The Raman spectra findings demonstrate the degree by which the tetragonal phase grows with the increase of calcining temperature in BZT-0.5BCT, and the characteristic ferroelectric-ferroelectric phase transition in BZT-xBCT while going through the MPB process. The structural and constituent evolution for the conversion process from gel to ceramic, as well as the formation mechanism of the BZT-0.5BCT crystallite, were also elucidated.Keywords gel, synthesized, ba, ti0, 8zr0, 2, crystallization, o3, ferroelectric, x, ba0, 7ca0, 3, tio3, thin, films, evolution, phase, properties, sol Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsWang, Z., Zhao, K., Guo, X., Sun, W., Jiang, H., Han, X., Tao, X., Cheng, Z., Zhao, H., Kimura, H., Yuan, G., Yin, J. & Liu, Z. (2013). Crystallization, phase evolution and ferroelectric properties of sol-gel-synthesized Ba(Ti0.8Zr0.2)O3-x(Ba0.7Ca0.3)TiO3 thin films. Journal of Materials Chemistry C, 1 522-530. AuthorsZeng-mei Wang, Kuan Zhao, Xin-li Guo, Wei Sun, Hua-long Jiang, Xue-qin Han, Xu-tang Tao, Zhen-xiang Cheng, Hong-yang Zhao, Hideo Kimura, Guo-liang Yuan, Jiang Yin, and Zhi-guo Liu nanocrystals was synthesized via a sol-gel method, and the corresponding thin films were also deposited on Pt/Ti/SiO 2 /Si substrates by a spin-coating approach. The BZT-xBCT thin film exhibited a high remnant polarization of 22.15 mC cm À2 with a large coercive field of 68.06 kV cm À1 . The resultant gel is calcined at various elevated temperatures and studied with FTIR/XRD/Raman/DSC-TGA/AFM/SEM techniques for gel composition, crystallization, phase transition, thermochemistry and the morphology of the film. Although the room temperature crystal structure of the BZT-xBCT nanocrystals appears to be a standard perovskite structure by conventional X-ray diffraction (XRD), Raman spectroscopy demonstrates the presence of non-centrosymmetric regions arising from the off-centering of the titanium (zirconium) atoms. The Raman spectra findings demonstrate the degree by which the tetragonal phase grows with the increase of calcining temperature in BZT-0.5BCT, and the...

A new series of ABO3-type perovskite photocatalysts MCo1/3Nb2/3O3 (M = Ca, Sr, and Ba) were synthesized by a solid-state reaction method, in which the B site is occupied by Co2+ and Nb5+ randomly in a charge-balanced manner. They were characterized by powder X-ray diffraction, UV−vis diffuse reflectance spectroscopy and photocatalytic activity measurements with Pt and NiO x cocatalyst under visible-light irradiation (λ > 420 nm), respectively. It is determined from the reflectance spectra that the optical transitions for these compounds, corresponding to visible-light absorption, are directly forbidden, and the band structures are suggested to be composed of the Co2+ 3d states and the Nb5+ 4d states. The feature of the electronic structure for BaCo1/3Nb2/3O3 calculated by the full potential-linearized augmented plane wave (F-LAPW) method shows that the O 2p states are strongly hybridized with the Co2+ 3d states, and little hybridized with the Nb5+ 4d states. The difference in their photocatalytic activity is ascribed to their special crystal and electronic structures.

We theoretically demonstrate that the two-dimensional porous C2N sheet exhibits an extremely high selectivity and large permeance in favour of H2 among other atmospheric gases. This experimentally available porous C2N is superior to traditional membranes, such as polymers and silica, and could have great potential for hydrogen separation.