Laser irradiation-induced α to δ phase transformation in Bi2O3 ceramics and nanowires

Vila, María; Dı́az-Guerra, C.; Piqueras, J.

doi:10.1063/1.4747198

Cited by 41 publications

(29 citation statements)

References 31 publications

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“…Presence of oxygen vacancies has been reported to shift the absorption spectra to longer wavelengths due to excitation of electrons from the donor levels of reduced Bi 3+ to the conduction band. 66 It was observed that the sample anodized at 20 V showed better optical absorbance of light in the wavelengths of 400-500 nm than other samples. The as-anodized sample showed wider bandgap than the annealed samples.…”

Section: Resultsmentioning

confidence: 97%

“…The absorbance at energy levels of 2.2-3.1 eV is usually attributed to the Bi 3+ intra-ionic electronic transitions and charge transfer transitions between oxygen ligands and Bi 3+ ions. 66 The minor absorbance shoulder observed at 2.7 eV could be attributed to the possible presence of sub carbonate phase in the sample. The optical absorption coefficient of Bi 2 S 3 has been reported to be around 2×10 5 cm −1 in the wavelength of 400-700 nm.…”

Section: Resultsmentioning

confidence: 98%

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Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Chitrada

Raja

Gakhar

et al. 2015

J. Electrochem. Soc.

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Bismuth oxide has well-dispersed valence bands that show enhanced mobility of charge carriers, high refractive index, and large dielectric constant. These properties are attractive for photo catalysis. Thin films of bismuth oxide containing vertically oriented and uniformly distributed nanopores of controllable dimensions were synthesized by a simple electrochemical anodization of a bismuth metal substrate in citric acid solution at 3-60 V. Annealing the anodic nanoporous Bi 2 O 3 at 200 • C for 2 h resulted in stabilization of the metastable β-Bi 2 O 3 phase at room temperature. The nanoporous anodic oxides showed an energy bandgap of 2.48 eV, and n-type semiconductivity. Scanning electron microscopy and electrochemical impedance spectroscopy results suggested a dual layered structure of the anodic oxide with a nanoporous outer layer and a planar inner layer. Thickness of the inner layer predominantly influenced the impedance of the anodic oxide. Under simulated 1-sun intensity, a maximum photo current density of 0.97 mA/cm 2 was observed in 1 M KOH at a potential of 1.53 VRHE for the sample anodized at 10 V. A positive shift in the flatband potential upon illumination suggested accumulation of photo generated holes due to low catalytic activity of the anodic bismuth oxide for oxygen evolution reaction. The observed photo current density of the nanoporous anodic oxide of bismuth was an order of magnitude higher than that of the planar anodic oxide, and twice that of thin film β-Bi 2 O 3 prepared by reactive sputtering.Synthesis of ordered arrays of nanoporous and nanotubular oxides of Al, Ti, and other valve metals has been investigated extensively because of their potential applications in solar energy conversion, energy storage, photocatalysts, sensors, and as templates for nanowire growth. 1-8 Enhanced photo catalytic, electrical, and electrochemical properties were reported for the nanoporous and nanotubular oxides, particularly TiO 2 and Fe 2 O 3 , when compared to their bulk crystalline counterparts. 9-14 Bismuth is different from regular valve metals such as Al, Ti, Nb etc., because of its semi-metallic nature and high atomic number with the electron configuration [Xe]4f 14 5d 10 6s 2 6p 3 . The large nuclear charge of bismuth increases the velocity of the 1s electrons to such an extent that the relativistic effect becomes significant which increases the mass of 1s electron by 26% and decreases the Bohr radius by 20%. Furthermore, the 6s electrons are less available for bonding. The normally degenerate p orbitals are split in to one spherically symmetric p 1/2 and two doughnut shaped p 3/2 orbitals because of the high degree of spin-orbit interaction. Since the p 3/2 orbitals have higher energy than p 1/2 , the p 3/2 electron is removed during first ionization of Bi resulting in an electron configuration of Bi(I) as 6s 2 6p 2 1/2 6p 0 3/2 . The major relativistic effects of bismuth are its lowest tendency to form a hybrid orbital and increasing tendency to form pyramidal structure. 15 The lone electron pa...

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 98%

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Chitrada

Raja

Gakhar

et al. 2015

J. Electrochem. Soc.

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“…The Bi 3+ intra-ionic electronic transitions and charge transfer transitions between oxygen ligands and Bi 3+ ions could be assigned to the observed band gaps. 41 The reported bandgap of the tetragonal β-Bi 2 O 3 is ∼2.5 eV and the monoclinic α-Bi 2 O 3 shows a bandgap of 2.8 eV. 19 The lower bandgap of the nanoporous Bi 2 O 3 indicated that the samples did not contain other high bandgap phases such as α (2.8 eV) or δ (3.1 eV), 42 and thus validating the XRD and Raman analysis data of the nanoporous oxide.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Performance of β-Bi₂O₃by In-Situ Photo-Conversion to Bi₂O₃-BiO_2-xComposite Photoanode for Solar Water Splitting

Chitrada

Gakhar

Chidambaram

et al. 2016

J. Electrochem. Soc.

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Ordered nanoporous bismuth oxide layer consisting of metastable β-Bi 2 O 3 phase that showed n-type semiconductivity was synthesized by a simple electrochemical anodization of bismuth substrate. When the anodic nanoporous β-Bi 2 O 3 samples were tested as photoanodes for solar water splitting application in 0.5 M Na 2 SO 4 (pH:5.8), and 1 M KOH (pH:13.7), the photocurrent decayed continuously with time from an initial value of 0.95 mA/cm 2 under 1-sun illumination at a bias potential of 1.5 V RHE . Accumulation of photo generated holes at the photoanode/ electrolyte was attributed to the photocurrent decay. Addition of methanol as sacrificial hole scavenger was not found to be effective for the bismuth oxide photoanodes. When hydrogen peroxide was added to the 0.5 M Na 2 SO 4 electrolyte, the photocurrent density increased to ∼4 mA/cm 2 and was stable for more than 1 h of illumination of AM1.5 global light at 1.5 V RHE . Addition of hydrogen peroxide to the 1 M KOH solution showed a gradual increase in the photocurrent density for the first 300 seconds of light illumination to a maximum value of ∼10 mA/cm 2 at 0.65 V RHE and then it decreased continuously. The high photocurrent density of nanoporous β-Bi Bismuth based mixed oxides such as BiVO 4 , BiFeO 3 , BiWO 6 , Bi 3 NbO 7 , and Bi 2 MoO 6 are being actively investigated as promising high efficiency photocatalysts for solar water splitting applications. 1-11These bismuth based oxides show predominantly n-type semiconductivity and therefore function as photoanodes in the photoelectrochemical water splitting process. A significant amount of literature is available on the photoelectrochemical behavior of bismuth based ternary oxides, however very few studies have reported the performance of the binary Bi 2 O 3 which is the elementary constituent of the advanced bismuth mixed oxides. The photocatalytic behavior of the bismuth based oxides is well documented and the factors that limit their performance is well understood. Most importantly they exhibit low catalytic activity for oxygen evolution, which results in hole accumulation at the electrode/electrolyte interface. In order to overcome this limitation, a thin layer of oxygen evolution catalysts such as Co-Pi, FeOOH, Ni(OH) 2 or CoPO 4 is usually coated on the photoanodes.12-17 The binary and ternary bismuth oxides show more or less similar electronic structures, where the valence bands of both binary Bi 2 O 3 , and mixed bismuth oxides are considered to be formed by O-2p and Bi-6s orbitals. 18,19 The top of the Bi-6s orbital is positioned at more negative potential than that of O-2p. [20][21][22] The conduction band of Bi 2 O 3 is predominantly formed by Bi-6p orbitals. Whereas, the conduction band of mixed bismuth oxide is determined by the d-orbitals of transitions metals present in the mixed oxide. Bismuth oxide shows enhanced mobility of charge carriers because of its well-dispersed valence bands and it has high refractive index and large dielectric constant due to lone electron pairs of Bi(III) 6s 2 that...

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“…It is possible to tune the electronic states of local sites on crystal surfaces by a high‐energy ion beam or laser irradiation . Laser irradiation has been utilized for inducing oxygen deficiency into TiO 2 , CaTiO 3 , and Sm 0.5 Ba 0.5 MnO 3 and for phase or structural transformation of α‐Al 2 O 3 to γ‐Al 2 O 3 , α‐Bi 2 O 3 to δ‐Bi 2 O 3 , tetragonal Cu 4 O 3 to monoclinic CuO, orthorhombic WO 3 ·H 2 O to monoclinic WO 3 , orthorhombic to monoclinic to cubic ZrO 2 , and tetragonal SrCuO 2 to orthorhombic SrCuO 2 …”

Section: Other Laser‐induced Phenomena In Metal Oxidesmentioning

confidence: 99%

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances

et al. 2018

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Recent technological advances in developing a diverse range of lasers have opened new avenues in material processing. Laser processing of materials involves their exposure to rapid and localized energy, which creates conditions of electronic and thermodynamic nonequilibrium. The laser-induced heat can be localized in space and time, enabling excellent control over the manipulation of materials. Metal oxides are of significant interest for applications ranging from microelectronics to medicine. Numerous studies have investigated the synthesis, manipulation, and patterning of metal oxide films and nanostructures. Besides providing a brief overview on the principles governing the laser-material interactions, here, the ongoing efforts in laser irradiation of metal oxide films and nanostructures for a variety of applications are reviewed. Latest advances in laser-assisted processing of metal oxides are summarized.

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Laser irradiation-induced α to δ phase transformation in Bi2O3 ceramics and nanowires

Cited by 41 publications

References 31 publications

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Enhanced Performance of β-Bi₂O₃by In-Situ Photo-Conversion to Bi₂O₃-BiO_2-xComposite Photoanode for Solar Water Splitting

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances

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Laser irradiation-induced α to δ phase transformation in Bi2O3 ceramics and nanowires

Cited by 41 publications

References 31 publications

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi2O3

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi2O3

Enhanced Performance of β-Bi2O3by In-Situ Photo-Conversion to Bi2O3-BiO2-xComposite Photoanode for Solar Water Splitting

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances

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Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Enhanced Photoelectrochemical Performance of Anodic Nanoporous β-Bi₂O₃

Enhanced Performance of β-Bi₂O₃by In-Situ Photo-Conversion to Bi₂O₃-BiO_2-xComposite Photoanode for Solar Water Splitting