Aurivillius Compound Research Articles

Efek Pendoping Nd3+ Pada Senyawa BaBi2-xNdxNb2O9 Terhadap Struktur, Sifat Dielektrik Dan Optik

The Aurivillius compound with formula BaBi2-xNdxNb2O9 (x = 0.05, 0.1, 0.2, and 0.4) has been successfully synthesized using the molten salt method, showing potential as a ferroelectric material. The impact of Nd3+ substitution on the structure, morphology, dielectric, and optical properties has been systematically analyzed. XRD data refinement confirms that BaBi2-xNdxNb2O9 (BBNN) exhibits an orthorhombic structure with an A21am space group. Anisotropic plate-like grains were observed across all samples, decreasing their size as Nd3+ content increases. The ferroelectric transition temperature (Tc) decreases due to structural distortion caused by the reduction of the lone pair 6s2 electron effect of Bi3+ when substituted with Nd3+. Moreover, this structural distortion also contributes to an increase in bandgap energy (Eg). The diffuse ferroelectric phase transition is characterized by a broadened Tc peak induced by Nd3+ substitution due to increased cationic disruption in the bismuth layers. The ferroelectric phase with a lower and broader Tc suggests that the x = 0.4 sample has the potential for electrocaloric applications.

Review On Strategies For the Design and Synthesis of Flower‐Like Bi2WO6 and BiOX (X=F, Cl, Br, I) Composites for Photocatalytic Environmental Remediation

AbstractIn latest events, water pollution has posed an immense threat, and its sustainable treatment is a topic of concern. Among myriad of water treatment, research community has lensed towards sustainable heterogeneous photocatalysis especially, inorganic semiconductors. Bismuth tungstate a pristine Aurivillius compound with unique crystal structure, exceptional photochemical stability, and strong redox abilities but minimum visible light absorption and quick carrier recombination are its caveats, these caveats are circumvented by synthesizing BiOX (X=F, Cl, Br and I) composites with surface modifiers, doping with hetero atoms (metals and non‐metals), construction of the heterojunction and amalgamation of carbon materials. The heart of this review is strategic engineering of flower‐like morphology photocatalyst synthesis and optical properties, it also discusses the charge transfer kinetics, photocatalytic performance, and durability. The flower‐like morphology highlighted in this review is due to its ability to harvest light, providing larger specific surface area which introduces more active sites and efficient excitons generation. The comprehensive tabulated data in this review will help the actively engaged research community in Bismuth heterogenous photocatalysis. It also sheds light on the future view of environmental remediation via photocatalytic developments.

Sintesis Lapis Empat Fasa Aurivillius Ca1-xBaxBi3,5La0,5Ti4O15 Dengan Metode Lelehan Garam

The four-layer Aurivillius phase Ca1-xBaxBi3.5La0.5Ti4O15 (x = 0.2, 0.4, 0.6, 0.8, and 1) has been synthesized by molten salt method. The effect of varying x on the structure, morphology, and dielectric properties was studied. X-ray diffraction (XRD) and Le Bail refinement revealed that the compounds with the composition x = 0, 0.2, and 0.4 were single-phase product with orthorhombic A21am structure, whereas for higher x value (composition of Ba doped), a Ba2TiO4 impurity is found in products. Changes in unit cell volume were investigated, and the size increased with larger x. The substitution of larger Ba2+ ions resulted in a shorter Ti-O bond, shifting vibration mode to higher wave number that showed in FTIR spectra. SEM images show anisotropic plate-like grain with distributed particle sizes at 1.9 – 3.1μm. The dielectric constant values decrease with increasing x, otherwise the dielectric loss values increase for x = 0 and 0.2, however decrease for x = 0.4. The resulting Aurivillius compound has potential for applications in ferroelectric and piezoelectric devices.

Interface Regulation of Bi3TiNbO9/Rh Photocatalysts by Introducing Ultrathin Heterolayer to Enhance Overall Water Splitting

AbstractAurivillius compounds‐based photocatalysts have attracted extensive interest largely due to their ferroelectric properties and modifiable characteristics arising from the alternate stacking of structural units. However, the interfacial Schottky barrier between such semiconducting compounds as light absorbers and metallic cocatalysts for hydrogen evolution restrains the transfer of photogenerated electrons, resulting in low photocatalytic overall water splitting activity and stability. Here, an anions‐induced surface structure transformation strategy is employed to modulate the interface structure between Bi3TiNbO9 as a typical Aurivillius compound and the cocatalyst Rh by in situ growing ultrathin Bi2MoO6 heterolayer on the surface of Bi3TiNbO9 nanosheets. The introduction of Bi2MoO6 heterolayer lowers the energy barrier near the Bi3TiNbO9 surface, which can facilitate the transfer of the photogenerated electrons from bulk to surface and thus the reduction of Rh cocatalyst for highly active hydrogen production. Compared with the Bi3TiNbO9‐Rh photocatalyst, the proportion of low‐valence metallic Rh0 in Bi2MoO6 heterolayer‐modified Bi3TiNbO9‐Rh (Bi3TiNbO9‐Bi2MoO6‐Rh) is improved by 7.76%, giving rise to a photocatalytic overall water splitting activity enhancement by a factor of 4.74. This strategy emphasizes the importance of interface regulation in promoting the transfer of photogenerated charge carriers in Aurivillius‐type photocatalysts, providing an effective pathway for designing and fabricating high‐performance photocatalysts.

Ferroelectric properties of vanadium substituted four-layer Aurivillius compound Bi5Fe1.5V0.5Ti2O15 thin films

We report the preparation and characterization of vanadium substituted four-layer Aurivillius compound Bi5Fe1.5V0.5Ti2O15 using spin coating method. Ferroelectricity in the prepared films are confirmed from the well saturated polarization vs electric field (P-E) loops having remnant polarization (2 Pr) around 12.94 µC/cm2 at room temperature. In addition, low temperature P-E measurements show a decrease in Pmax and 2 Pr, which is attributed to the stabilization of defect dipole complexes and domain pinning, as seen in bismuth-based ferroelectrics. Additionally, this decrease in polarization is accompanied by an increase in imprint, confirming the presence of defect dipoles manifested as internal fields.

Study of La substituted four-layer Aurivillius compound Bi$$_5$$FeTi$$_3$$O$$_{15}$$

Study of La substituted four-layer Aurivillius compound Bi$$_5$$FeTi$$_3$$O$$_{15}$$

Room-temperature multiferroic behavior in the three-layer Aurivillius compound Bi3.25La0.75Ti2Nb0.5(Fe1-x Cox)0.5O12

Room-temperature multiferroic behavior in the three-layer Aurivillius compound Bi3.25La0.75Ti2Nb0.5(Fe1-x Cox)0.5O12

Synthesis and characterization of plate-like vanadium doped SrBi4Ti4O15 prepared via KCl molten salt method

SrBi4Ti4O15 is one of four-layered Aurivillius compound family member that can be used as photocatalyst material that works in the violet light region. To expand its work function range can be conducted by doped with metal elements to SrBi4Ti4O15 as results reduced its band gap energy. In this research, we synthesized vanadium doped SrBi4Ti4O15 (SrBi4Ti4-nVnO15 (n= 0, 0.05, 0.1, and 0.15)) by molten salt method (used KCl salt). The diffractogram sample showed that the target compounds SrBi4Ti4-nVnO15 (n= 0, 0.05, 0.1, and 0.15) had been successfully synthesized with the space group A21am without impurities. The SEM micrographs showed the particle shape of SrBi4Ti4-nVnO15 (n= 0, 0.05, 0.1, and 0.15) was plate-like (sheets) and V dopant did not cause agglomeration. The result of Kubelka-Munk equation calculation showed that the V dopant can reduced the band gap energy value from 3.04 eV (408 nm) to 2.84 eV (437 nm)

First-principles study on structural, electronic and ferroelectric properties of Bi2VO5.5 compound

A first-principles investigation of the origin of ferroelectricity in the Aurivillius compound Bi2VO5.5 is presented. Calculations with the density functional theory, in conjunction with the modern theory of polarization, allowed us to study the structural, electronic, and polar properties of two configurations built with oxygen vacancies, causing a charge imbalance and a subsequent displacement of the ions, generating two maximum polarizations, one of 14.75 μC/cm2 and one of 4.31 μC/cm2 along [011] direction. Electron localization function schemes were used to identify the asymmetry of charges in (001), (010) and (100) planes. The results obtained in this study establish that the origin of ferroelectricity is due to the displacement of the ions caused by oxygen vacancies and the asymmetric distribution of the isolated pair of Bi ions. On the other hand, the bandgap calculations and the results of Ps establish that Bi2VO5.5 is a candidate ferro-photovoltaic material.

Magnetism in four-layered Aurivillius Bi[formula omitted]FeTi[formula omitted]O15 at high pressures

We report the structural and magnetic properties of four-layer Aurivillius compound Bi5FeTi3O15 (BFTO) at high hydrostatic pressure conditions. The high-pressure x-ray diffraction (XRD) data does not explicitly show structural phase transitions with pressure, however the observed changes in lattice parameters indicate structural modifications at different pressure values. In the initial pressure region values (up to 2.2 GPa), the lattice parameters a- and b- are nearly equal implying a quasi-tetragonal structure, however as the pressure increases a- and b- diverges apart and exhibits complete orthorhombic phase at pressure values of about ≥8 GPa. Principal component analysis (PCA) of high pressure Raman measurements point out an evident change in the local structure at about 5.5 GPa indicating that the evolution of the local structure under applied pressure seems to not follow crystallographic changes (long range order). Nuclear forward scattering (NFS) measurements reveal the development of magnetic ordering in BFTO at 5K with high pressures. A progressive increase in magnetic order is observed with increase in pressure at 5 K. Further, NFS measurements carried out at constant pressure (6.4 GPa) and different temperatures indicate that the developed magnetism disappears at higher temperatures (20 K). It is attempted to explain these observations in terms of the observed structural parameter variation with pressure.

Aurivillius compound Bi5Ti3CrO15 as a visible-light-active photocatalyst for hydrogen production from water

Layered Aurivillius compound Bi5Ti3CrO15 has been synthesized by a hydrothermal method for the application as a photocatalyst to liberate hydrogen from water. Bi5Ti3CrO15 owns a narrow band gap (Eg ~2.46 eV) and shows stable photocatalytic activity under both full range (λ ≥250 nm) and visible light illumination (λ ≥420 nm). A short hydrothermal reaction time is critical to achieve high photocatalytic activity as defects such as Cr6+ and Bi5+ can be avoided. An AQE as high as 3.66% at 420 nm ± 20 nm has been recorded, warranting promising application in the field of solar energy conversions. DFT calculation reveals the important role of Cr3+cations for visible light sensitivity of Bi5Ti3CrO15.

The Effect of Temperature Synthesis on the Plate-Like Particle of Bi4Ti3O12 Obtained by Single Molten NaCl Salt

Three-layer Aurivillius compound bismuth titanate (Bi4Ti3O12) is well known for having interesting properties such as ferroelectric and photocatalyst. Many researchers reported that the unique plate-like shaped particle affecting ferroelectric and photocatalyst properties. The molten salt synthesis is the common simple method to obtain that unique morphology. In this research, Bi4Ti3O12 was synthesized using single molten salt NaCl at various temperatures, which is 800, 850, 900, and 950 oC. X-Ray Diffraction data showed that all obtained Bi4Ti3O12 have a B2cb space group with no impurities detected. The Raman spectra shows the characteristic vibration modes of Bi4Ti3O12 at 62, 117, 228, 269, 332, 364, 536, 851 cm-1. The plate-like shaped particle was confirmed by SEM analysis. Based on SEM images, the size of the particle increased along with the synthesis temperature, which is due to the thermal effect on grain growth.

Modified room‐temperature magnetic and optical properties in bilayer xBi6Fe2Ti3O18 − (1−x)CoFe2O4 composite thin films

Heterogeneous bilayer of Aurivillius compound Bi6Fe2Ti3O18 (BFTO) and Cubic spinel structure CoFe2O4 (CFO), a class of highly effective multiferroic composites, have been synthesized on fused quartz substrate by sol–gel method. Both BFTO and CFO layers are synthesized separately without any chemical reaction which can be confirmed by XRD pattern and Raman spectroscopy for two individual sets of maps. SEM and AFM images also verify two separate layers by showing the boundary between two layers clearly. Furthermore, linear increased ferromagnetism with increasing CFO component has been detected, further proving the independence of BFTO and CFO phases. Non-linear changed electron transition energy has been observed which may be derived from the crystal field distortion at the interface of the two layers. Therefore, an appropriate component can be found which have both excellent magnetic and optical properties, showing great potential on solar-energy conversion devices and multiferroic applications. In addition, variable temperature transmission spectra have been detected and the results are worth to be analyzed deeply.

Multiferroic properties of three-layer Aurivillius compound Bi[formula omitted]TiFeNbO12: A first-principles and experimental study

We present a first-principles and experimental study of the structural, ferroelectric, and magnetic properties of the potentially multiferroic three-layer Aurivillius compound Bi4TiFeNbO12. This system can be realized by inserting a BiFeO3 formula unit into the two-layer Aurivilius Bi3TiNbO9 matrix. The calculations are performed using the PBEsol exchange–correlation functional within the DFT+U framework. First we search for potential cation site preference by comparing the relative stability of different Fe, Nb and Ti arrangements. We find a preference for the Fe3＋ ions to occupy the inner site within the pseudoperovskite block. This configuration exhibits a band gap of 1.2 eV (UFe=4eV) and ferroelectric and magnetic orders. A value of 66 μC/cm2 is obtained for the spontaneous polarization, which is similar to the one obtained for Bi4Ti3O12 (BIT). The magnetic ground state of this system is characterized by a strong antiferromagnetic coupling between the Fe3＋ ions located in the central layer. By mapping to a Heisenberg model, the superexchange antiferromagnetic coupling between nearest-neighbor Fe3＋ cations is estimated to be J=53 meV. Finally, we synthesize Bi3.25La0.75TiFeNbO12 ceramics by the solid-state reaction method. Their structural, electric and magnetic properties are confronted with the theoretical predictions.

Sintesis Bi4Ti3O12 Terdoping Vanadium dengan Metode Lelehan Garam Tunggal NaCl

Bi4Ti3O12 merupakan senyawa Aurivillius lapis 3 yang berpotensi sebagai material fotokatalis dengan energi celah pita 2,9 eV (427 nm). Untuk memperluas pemanfaatannya, maka energi celah harus diturunkan. Salah satu usaha untuk menurunkan energi celah pita adalah dengan teknik pendopingan logam. Dalam penelitian ini, kami melakukan pendopingan logam vanadium pada Bi4Ti3O12 (Bi4Ti3-xVxO12 (x= 0, 0,05; 0,1; 0,15, dan 0,2)) dengan metode lelehan garam. Data difraktogram menunjukkan fasa Bi4Ti3O12 terbentuk dengan fasa pengotor BiNaO3 dan NaV6O11. Hasil karakterisasi dengan menggunakan Scanning Electron Microscopy (SEM) menunjukkan bahwa bentuk partikel Bi4Ti3O12 adalah plate-like. Hasil karakterisasi dengan menggunakan ultraviolet (UV)-visible (Vis) Diffuse Reflectance Spectroscopy (UV-Vis DRS) menunjukkan bahwa sampel yang diperoleh mempunyai energi celah pita yang lebih rendah dibandingkan dengan Bi4Ti3O12. Kata kunci: Bi4Ti3O12, dopant vanadium, energi celah

Voigt Fitting is of Special Interest for Impedance and Raman Spectroscopic Analysis for Two-Layered Aurivillius Compound

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Structural, dielectric, impedance and modulus spectroscopy of BiLa2TiVO9 ceramic

A standard solid-state ceramic technology (i.e., high-temperature solid-state reaction method) was used to fabricate new bismuth layer Aurivillius compound, BiLa2TiVO9. The formation of a single phase with an orthorhombic structure was confirmed by the X-ray diffraction structural analysis. The tangent loss measured at 200 °C is found to be in between 0.03 and 0.05 in the frequency ranging from 1 kHz to 1 MHz. The dielectric constant is found to be around 300 at room temperature. The resistance and reactance parts of complex impedance have been determined by the complex impedance spectroscopy (CIS) techniques. The electric modulus spectroscopy study of the compound confirmed the presence of the short range displacement of charge carriers. Jonscher’s power law fitting has been used to verify our experimental data of conductivity spectra. The nature of variation of exponent (n) obtained from the fitting follows the correlated barrier hopping as the predominant conduction mechanism in the sample. Room-temperature polarization loop confirms the ferroelectric nature of the sample.

Effect of W/Co co-substitution on structural, microstructural, magnetic and electrical properties of Bi4NdFeTi3O15 aurivillius compound

Here, in this paper, we have reported the structural, microstructural, optical, ferroelectric and magnetic properties of Nd and W/Co co-substituted Bi4NdTi3−2x(W/Co2)xFeO15 (0.00 ≤ x ≤ 0.15) 4-layered Aurivillius multiferroic ceramics. These ceramics were prepared by conventional high-temperature solid-state reaction method. The room temperature (RT) X-ray diffraction (XRD) and Raman studies revealed that, these ceramics exhibits a pure orthorhombic structure with A21am space group. The surface morphology of these ceramic studies confirmed the formation of randomly oriented grains as non-uniform in size. Further, W/Co2 substitution in BNFT revealed the presence of asymmetrical shaped internal nano-size domains. The band gap of the ceramics was calculated and found to be decreased upon with increasing the concentration of W/Co2. All compounds exhibited improved P–E loops with unsaturated polarization upon substitution with enhance polarization and reduced coercive field. It was found that with higher substitution levels x ≥ 0.10 adversely affected the ferroelectric characteristics. The magnetic measurement revealed that Nd and W/Co co-substitution induced a strong ferromagnetic interaction via Fe3+–O–Co2+/3+ coupling. The high-temperature magnetization studies revealed the Curie temperature (TC) enhances as the W/Co2 concentration increase. Henceforth, the observed outcomes are emphasized for designing new single-phase room temperature multiferroics in future magnetoelectric applications.

Structural and multiferroic properties in double-layer Aurivillius phase Pb0.4Bi2.1La0.5Nb1.7Mn0.3O9 prepared by molten salt method

A single-phase sample of the Aurivillius compound Pb0.4Bi2.1La0.5Nb1.7Mn0.3O9 was prepared by a molten salt method using K2SO4/Na2SO4 as the flux. The crystal structure, morphology, ferroelectric, and magnetic properties were investigated. Neutron powder diffraction data confirmed a non-centrosymmetric orthorhombic crystal structure with space group A21am and Pb/Bi disorder in the bismuth oxide blocks, Bi/Pb/La disorder on the perovskite A-site, and Nb/Mn disorder on the perovskite B-site. The morphology of the sample showed anisotropic plate-like grains as probed by scanning electron microscopy. The dielectric constant exhibits a transition peak between 600 K and 640 K that depends on frequency, indicating relaxor ferroelectric behavior. Electrical polarization versus applied field loops are unsaturated, with a remnant polarization of 0.43 μC/cm2 at 40 Hz under the maximum electrical field applied of 160 kV/cm. The ferroelectricity originates from the displacement of oxygen atoms in the BO6 octahedra, resulting in a polar structural distortion. Magnetic susceptibility measurements showed the presence of mixed Mn3+ and Mn4+, resulting in short-range ferromagnetic order via double exchange interactions below 33 K. The remnant magnetization (Mr) is 0.01 emu/g at 5 K. This mixed valence of Mn cations is mainly responsible for the high electrical conductivity. Thus, Pb0.4Bi2.1La0.5Nb1.7Mn0.3O9 exhibits coexisting ferroelectric and ferromagnetic properties.

The Aurivillius Compound CoBi2O2F4 – an Efficient Catalyst for Electrolytic Water Oxidation after Liquid Exfoliation

AbstractInvestigation of new high‐efficiency catalysts for the oxygen evolution reaction (OER) is important for propelling the practical applications of water splitting. Here we report the Aurivillius compound CoBi2O2F4 to be a novel catalyst for catalytic OER. After liquid exfoliation of CoBi2O2F4 crystals in isopropanol, the resulting thin sheets deliver a low overpotential of 334 mV and a small Tafel slope of 47 mV dec−1 for catalytic OER, exhibiting substantially higher activity and faster kinetics compared with as‐synthesized crystals. This attributes to the increase in accessible surface area and dangling bonds on the edges providing more active sites exposed on the surface after exfoliation. The positive effects of F− anions to benefit OH− adsorption/combination and p‐block Bi3+ cations to direct reactants to preferred sites are proposed to synergistically improve the Co‐active centers for catalysis; based on this, the OER reaction mechanism on this new catalyst is discussed.