Crystal Engineering of Bi2WO6 to Polar Aurivillius-Phase Oxyhalides

The Aurivillius phases of complex bismuth oxides have attracted considerable attention due to their lattice polarization (ferroelectricity) and photocatalytic activity. We report a first-principles exploration of Bi2WO6 and the replacement of W6+ by pentavalent (Nb5+, Ta5+) and tetravalent (Ti4+, Sn4+) ions, with charge neutrality maintained by the formation of a mixed-anion oxyhalide sublattice. We find that Bi2SnO4F2 is thermodynamically unstable, in contrast to Bi2TaO5F, Bi2NbO5F and Bi2TiO4F2. The electric dipoles introduced by chemical substitutions in the parent compound are found to suppress the spontaneous polarization from 61.55 μC/cm2 to below 15.50 μC/cm2. Analysis of the trends in electronic structure, surface structure, and ionization potentials are reported. This family of materials can be further extended with control of layer thicknesses and choice of compensating halide species.

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Anion Ordering in CaTaO2N: Structural Impact on the Photocatalytic Activity. Insights from First-Principles

Chemistry of Materials ◽

10.1021/acs.chemmater.6b03366 ◽

2017 ◽

Vol 29 (2) ◽

pp. 539-545 ◽

Cited By ~ 32

Author(s):

Ayako Kubo ◽

Giacomo Giorgi ◽

Koichi Yamashita

Keyword(s):

Photocatalytic Activity ◽

First Principles ◽

Structural Impact

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First-Principles Study on Electronic and Optical Properties in Pr-Doped Anatase TiO2

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.924.260 ◽

2014 ◽

Vol 924 ◽

pp. 260-268 ◽

Cited By ~ 1

Author(s):

Hao Chen ◽

Lan Fang Yao ◽

Song Lin Yang ◽

Ya Qin Wang ◽

Xing Liang ◽

...

Keyword(s):

Optical Properties ◽

Photocatalytic Activity ◽

First Principles ◽

Energy Gap ◽

Impurity Band ◽

Anatase Tio2 ◽

Electron Hole ◽

Light Region ◽

Overlap Population ◽

Calculation Results

The crystal structures, band structures, density of states, charge density, overlap population and optical properties of pure anatase TiO2 and Pr-doped anatase TiO2 were studied by using the plane-wave pseudopotential method based on the first-principles. After Pr doping, the valence band and the conduction band moved down and became dense, energy gap became narrow and a impurity band which consists of Pr 4f states appeared. And the dipole moment got improved, which is good for the separate of the electron-hole pairs. These effectively overcome two huge shortcomings of TiO2. Besides, Pr-doped anatase TiO2 produced more carriers which have good transport properties and the absorption spectra of Pr-O bond appear in the region that the wavelength is longer. The calculation results of optical properties show that the absorption edge occured red shift, which means the photocatalytic activity of anatase TiO2 got remarkable improved during visible-light region. This conforms to the previous analysis. So the photocatalytic activity of anatase TiO2 got remarkable improved after Pr doping.

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Combined first-principles calculations and experimental study on the photocatalytic mechanism of natural dolomite

RSC Advances ◽

10.1039/d1ra04525c ◽

2021 ◽

Vol 11 (39) ◽

pp. 24416-24423

Author(s):

Xiaomin Hou ◽

Qi Cheng ◽

Jianrong Wang ◽

Qingfeng Wu ◽

Weibin Zhang

Keyword(s):

Experimental Study ◽

Photocatalytic Activity ◽

First Principles ◽

Low Cost ◽

Isomorphous Substitution ◽

First Principles Calculations ◽

Photocatalytic Mechanism

Natural dolomite exhibits notable photocatalytic activity due to the isomorphous substitution of Fe2+ for Mg2+ in the lattice, implying that it can be used as a low-cost photocatalyst.

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Hydrothermal synthesis of ABi2Ta2O9Aurivillius phase: A comparative study of A-site cation size on structure, dielectric, optical properties

Journal of Advanced Dielectrics ◽

10.1142/s2010135x21500302 ◽

2021 ◽

Author(s):

Ilona Bella ◽

Tio Putra Wendari ◽

Novesar Jamarun ◽

Nandang Mufti ◽

Zulhadjri

Keyword(s):

Xrd Analysis ◽

Aurivillius Phase ◽

Hydrothermal Route ◽

Orthorhombic Crystal ◽

Ionic Radii ◽

Aurivillius Phases ◽

Orthorhombic Crystal Structure ◽

A Site ◽

Cation Size ◽

Ferroelectric Transition Temperature

In this study, the double-layered Aurivillius phases CaBi2Ta2O9 (CBT) and PbBi2Ta2O9 (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an [Formula: see text]21am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca[Formula: see text] compared to Pb[Formula: see text]. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of [Formula: see text]-site cations (Ca[Formula: see text] and Pb[Formula: see text] strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca[Formula: see text] cations induced a higher structural distortion, which resulted in higher bandgap ([Formula: see text] energy and ferroelectric transition temperature ([Formula: see text] of CBT, compared to those of PBT.

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