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Low Frequency Dielectric Relaxation and Charge Transport in Bi<sub>12</sub>TiO<sub>20 </sub>Photorefractive Sillenite Crystals
摘要： Features of processes of a dielectric relaxation and charge transport in photorefractive sillenite crystals Bi12TiO20 at low frequency range are investigated. It was found that the dispersion of dielectric permittivity ε' in crystals Bi12TiO20 is characterized by its growth with lowering frequency and rising temperature. This behaviour may be related to existence of dipole-relaxation polarization mechanism. The frequency dependence of dielectric loss tgδ reveals the existence of low frequency relaxation peaks in the studied temperature range. From the conductivity dependence on the frequency and temperature it was found that conductivity σ increases as frequency increases in the low frequency range. The observed dependence σ(ω)≈Аωs indicates that transport mechanism is due to hopping of carriers via localized electron states. The charge transport is thermally activated process in which activation energy Ea = (0.82±0.03) eV.
关键词： Charge transport,Photorefractive Sillenite crystals,Dielectric relaxation
更新于2025-09-23 15:21:21
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Structural, Electrical and Morphological Properties of Materials Type Sillenite Phase Bi12TiO20
摘要： This work reports the investigation of the ternary system Bi2O3–TiO2–MgO. Some compositions have been synthesized by solid state reaction at 800?°C and characterized by powder X-ray diffraction. The doping of (α-Bi2O3) allowed us to stabilize three compositions isotype of sillenite structure phase with formulas Bi0.9 Ti0.1 O1.55, Bi0,9 Ti0,05Mg0,05 O1,5, and Bi0.8 Mg0.1 Ti0.1 O1.5. The structural resolution of the synthesized materials was performed using Rietveld method by means of FullProf program. It crystallizes in the cubic system. The space group I23 and lattice parameter a = 10.1723(2) ?. The morphological proprieties of the synthesized compositions have been investigated by means of scanning electron microscopy (SEM). Sintered samples showed a dense and uniform microstructure. The density of sintered samples obtained is nearly 92% of the theoretical density. Various impedance model including capacity and Warburg impedances have been used to interpret the Nyquist representations of electrical analyses. The highest conductivity is observed for Bi0.9 Ti0.1 O1.55 (σ = 1.39E?07 at 600?°C).
关键词： Electrical Impedance,SEM,Spectroscopy,X-ray diffraction,Sillenite
更新于2025-09-23 15:21:21
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Facile synthesis of Ag Bi25GaO39Bi2WO6 heterostructure with enhanced photocatalytic performance based on interface structure design
摘要： Composite photocatalytic system based on interface structure design is deemed to be a feasible method to improve the photocatalytic efficiency of sillenite-type photocatalytic material. Therefore, we reported the successful construction of novel tetrahedron-like Ag–Bi25GaO39–Bi2WO6 heterostructure through a partial chemical conversion strategy coupling with the photo-reduction method. Experiment indicated that the as-prepared Ag–Bi25GaO39–Bi2WO6 heterogeneous structure possessed excellent photo-degradation activity for the decomposition of Rhodamine B (RhB) and 95% of RhB molecules could be decomposed after 20 min of UV–vis light irradiation by comparison of single Bi25GaO39 and Bi2WO6, as well as the Bi25GaO39–Bi2WO6 heterostructure. Moreover, the resulted Ag–Bi25GaO39–Bi2WO6 product also exhibited outstanding photocatalytic activity for the decomposition of other pollutant such as phenol and toxic Cr(VI) solutions. Due to the resulted advantages derived from the rational design of interface structure (matching band structure, intimate interfacial contacts, 'face-to-face' contact mode of hetero-interface and the famous 'schottky barriers'), the photo-generated charges generated in the composite photocatalytic system could be separated quickly, thus exhibiting excellent photocatalytic ability. This design concept can provide new ideas for the construction of other similar composite photocatalytic systems.
关键词： Sillenite,Tetrahedron,Interface structure design,Photocatalysis
更新于2025-09-19 17:15:36
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Synthesis of sillenite-type Bi36Fe2O57 and elemental bismuth with visible-light photocatalytic activity for water treatment
摘要： With Fe(NO3)3$9H2O and Bi(NO3)3$5H2O as raw materials, different sillenite-type compounds and elemental bismuth were prepared by a facile one-pot solvothermal method using H2O, C2H5OH, (CH2OH)2 and C3H8O3 as solvents, respectively. The structure, morphology, elemental compositions and properties of samples were examined by XRD, SEM, TEM, ICP, XPS, N2 adsorption and desorption, UV-vis DRS and PL. The photocatalytic activities of different samples were evaluated by the photodegradation of RhB under visible-light irradiation (l> 400 nm), and results show that Bi36Fe2O57 prepared using C2H5OH as the solvent owns the optimum performance. In order to explore the reaction mechanism, an additional experiment was designed to investigate the main active species during the photodegradation process via dissolving different trapping agents in the reaction solution before light irradiation. The results show that superoxide radical anions play a major role in this system since the RhB degradation was signi?cantly suppressed after the addition of benzoquinone.
关键词： Bi36Fe2O57,elemental Bi,sillenite,photocatalysis
更新于2025-09-10 09:29:36