The metallic 1T-WS2 as cocatalysts for promoting photocatalytic N2 fixation performance of Bi5O7Br nanosheets

Recently, widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure. However, owing to the fast carrier recombination, the photocatalytic performance of BiOX materials is not so satisfactory. Loading 1T phase WS₂ nanosheets (NSs) onto Bi₅O₇Br NSs can improve the photocatalytic N₂ fixation activity. Among these, the obtained 1T-WS₂@Bi₅O₇Br composites with optimum 5% 1T-WS₂ NSs display a significantly improved photocatalytic N₂ fixation rate (8.43 mmol L⁻¹ h⁻¹ g⁻¹), 2.51 times higher than pure Bi₅O₇Br (3.36 mmol L⁻¹ h⁻¹ g⁻¹). And the outstanding stability of 1T-WS₂@Bi₅O₇Br-5 composites is also achieved. Exactly, the photoexcited electrons from Bi₅O₇Br NSs are quickly transferred to conductive 1T phase WS₂ as electron acceptors, which can promote the separation of carriers. In addition, 1T-WS₂ NSs can provide abundant active sites on the basal and edge planes, which can promote the efficiency of photocatalytic N₂ fixation. This work offers a novel solution to improve the photocatalytic performance of Bi₅O₇Br NSs.     

Studying photocatalytic dye degradation with bismuth nitrate–derived catalysts using paper microzones method

We study the effect of calcination temperatures on photocatalytic dye degradation performance of bismuth nitrate materials using paper microzone method. The calcination forms different photoactive bismuth compounds such as α-Bi₂O₃, Bi₅O₇NO₃, and (BiO)₄CO₃(OH)₂, which are responsible for photocatalytic activity. We show that using basic magenta as a model pollutant is beneficial to more accurately determine the effects brought by different quenching agents on photocatalytic activity, compared with salicylic acid, which is a colorless and refractory pollutant. Our results may provide important insights into developing a model system to study the photocatalytic activity of various catalytic systems and to develop effective water treatment methods.     

自掺杂改性Bi_4O_5X_2(X=Br,I)异质结催化剂的合成及在油田废液处理上的应用

通过调控原料中五水硝酸铋和卤源的比例制备了自掺杂改性Bi_4O_5X_2(X=Br, I)光催化材料,Bi_4O_5X_2(X=Br,I)光催化性能得到明显提升.分别用X射线衍射仪分析催化剂的晶体结构、环境扫描电子显微镜观测催化剂的形貌、紫外可见漫反射分光光度仪测试催化剂的光吸收性能、 ST-MP-9全自动比表面积测试仪测试催化剂的比表面积.通过测定光降解油田污染物丙烯酰胺的吸光度值和化学需氧量(COD)值的变化研究了催化剂的催化活性.结果表明,经过5 h的紫外可见光光降解反应,Bi_4O_5Br_2-Bi2.6降解丙烯酰胺的性能最好,降解率达到58.2%、 COD值降低87.1%.     

Bi5O7Br and its structural relation to α‐Bi5O7I

Pentabismuth heptoxide bromide, Bi₅O₇Br, crystallizes in the space group Cmca. Its structure is compared with the closely related Ibca structure of α‐Bi₅O₇I. The change in the space group is assumedly the result of a compromise between the different spatial needs of Br and I and the rigidity of the {³_∞}[Bi, O] frameworks into which they are embedded. A detailed procedure for the synthesis of Bi₅O₇Br is given.     

A new bismuth potassium nitrate oxide, Bi1.7K0.9O2(NO3)2: Synthesis, structure, thermal behavior, and photocatalytic properties

We report here the first observation of a bismuth potassium nitrate Bi_1.7K_0.9O₂(NO₃)₂, obtained via thermal decomposition of bismuth and potassium nitrate mixtures. The new compound is orthorhombic, space group Immm (71), Z = 2, with a = 3.8698(7) Å, b = 3.8703(7) Å, and c = 24.1271(4) Å. Its crystal structure was refined from powder X-ray diffraction data by analogy with the mineral beyerite, Bi₂O₂Ca(CO₃)₂. The morphology and elemental composition of Bi_1.7K_0.9O₂(NO₃)₂ were characterized using scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS). Its phase transformations upon heating and products of its thermal decomposition were studied using XRD, TGA and FTIR. At 440 °C, Bi_1.7K_0.9O₂(NO₃)₂ transforms to another basic bismuth potassium nitrate with demonstrates a very similar XRD pattern but slightly larger cell parameters. At 520 °C, the intermediate oxide nitrate decomposes into a mixture of crystalline α-Bi₂O₃ and KNO₃. The as prepared Bi_1.7K_0.9O₂(NO₃)₂ showed lower than TiO₂ (Degussa P25) photocatalytic activity upon decomposition of a widely used model pollutant, Rhodamine B (RhB) and photooxidation of potassium iodide under UV-vis light irradiation. Interaction with potassium iodide in alkaline media resulted in formation of Bi₅O₇I.     

Thermal Stability,Microstructure and Photocatalytic Activity of the Bismuth Oxybromide Photocatalyst

Flake BiOBr was first prepared by a solution method at room temperature. Then, the produced BiOBr was calcined at different temperatures. It was found that BiOBr is not a stable compound. It transforms to plate‐like Bi₂₄O₃₁Br₁₁at around 750°C and the formed Bi₂₄O₃₁Br₁₁ can further convert to rod‐like α‐Bi₂O₃ at around 850°C. The prepared compounds were characterized with X‐ray diffraction (XRD), N₂ physical adsorption, scanning electron microscopy (SEM), and UV‐Vis diffuse reflectance spectra (DRS), respectively. The photocatalytic activity of the produced bismuth oxybromides was evaluated by photocatalytic decomposition of acid orange II under both visible light (λ>420 nm) and UV light (λ=365 nm) irradiation. Results show that these compounds have different band gaps and different photocatalytic properties. The band gap energies of the as‐prepared samples were found to be 2.82, 2.79, 2.60 and 3.15 eV for BiOBr, BiOBr/Bi₂₄O₃₁Br, Bi₂₄O₃₁Br, and α‐Bi₂O₃, respectively. Under both UV light and visible light irradiation, the photocatalytic activity follows the order: BiOBr/Bi₂₄O₃₁Br mixture>BiOBr>Bi₂₄O₃₁Br>α‐Bi₂O₃. The change in photocatalytic activity could be attributed to the different light absorption ability and microstructures of the photocatalysts.     

Bi_(12)O_(17)Br_2和Bi_4O_5Br_2纳米片的简易制备及光催化氧化NO机理的原位漫反射红外光谱研究(英文)

BiOBr因具有合适的能带结构和独特的层状纳米结构而广泛应用于可见光催化领域,但其低的可见光利用率和高的光生电子-空穴对复合率,限制了其实际应用.最近,非整比BiOBr纳米材料表现出了良好的可见光催化性能.本课题组分别采用简易水热法和常温法制备得Bi_(12)O_(17)Br_2和Bi_4O_5Br_2纳米片,并表现出良好的可见光催化性能.然而,对于Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的可见光催化氧化NO的转化路径及反应机理还不清楚.基于此,本文采用射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、电子自旋共振(ESR)、电子顺磁共振(EPR)和比表面积-孔结构(BET-BJH)等手段研究了Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的理化性能,通过原位红外光谱(in situ DRIFTS)研究了Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的可见光催化氧化NO的转化路径及反应机理.XRD结果表明,在常温碱性环境下,OH~-离子逐步取代BiOBr中的Br-离子制备得单斜晶相Bi_4O_5Br_2;在水热碱性环境下,OH-离子进一步取代Bi_4O_5Br_2中的Br-离子制备得四方晶相Bi_(12)O_(17)Br_2.SEM和TEM结果表明,Bi_(12)O_(17)Br_2是由不规则纳米片堆叠形成的紧密且厚实的层状结构,Bi_4O_5Br_2是由纳米片和纳米颗粒无序堆积形成的多孔疏松结构.BET-BJH测试结果显示,Bi_4O_5Br_2的比表面积和孔容(37.2 m~2/g,0.215 cm~3/g)显著高于Bi_(12)O_(17)Br_2(8.7 m~2/g,0.04 cm~3/g).UV-Vis DRS测试结果显示,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2均显示了良好的可见光吸收能力.可见光催化去除NO的测试结果表明,Bi_4O_5Br_2(41.8%)的光催化活性明显高于Bi_(12)O_(17)Br_2(28.3%).并且,在5次可见光催化循环实验后,Bi_4O_5Br_2(41.1%)表现出良好可见光催化稳定性.ESR测试结果表明,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2参与反应的主要活性物种均为·OH自由基,Bi_4O_5Br_2产生·OH自由基明显强于Bi_(12)O_(17)Br_2.EPR测试结果表明,Bi_4O_5Br_2的氧空位明显多于Bi_(12)O_(17)Br_2,丰富的氧空位更有利于NO的有效吸附.由此可见,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2表现出不同的理化特性.可见光催化氧化NO的原位红外光谱表明,只在Bi_(12)O_(17)Br_2光催化氧化NO的转化路径中会生成中间产物N2O3,表明Bi_(12)O_(17)Br_2和Bi_4O_5Br_2具有不同的NO光催化转化路径.结合上述表征结果认为,Bi_4O_5Br_2比Bi_(12)O_(17)Br_2表现出更优异可见光催化性能的主要原因有以下四个方面为:(1)Bi_4O_5Br_2拥有更高的比表面积和更大的孔容,有利于NO的吸附、反应中间产物的转移和提供更多的活性位点参与光催化反应;(2)Bi_4O_5Br_2可以生成更多的·OH自由基和拥有更强的价带空穴氧化能力;(3)NO中的O原子可以与Bi_4O_5Br_2的氧空位结合,从而提供更多的反应位点;(4)Bi_4O_5Br_2的光催化反应中可以生成中间产物N_2O_3,可以降低NO转化成NO_3~-的反应活化能.     

A Bi/BiOI/(BiO)2CO3 heterostructure for enhanced photocatalytic NO removal under visible light

Narrow-band BiOI photocatalysts usually suffer from low photocatalysis efficiency under visible light exposure because of rapid charge recombination. In this work, to overcome this deficiency of photosensitive BiOI, oxygen vacancies, Bi particles, and Bi₂O₂CO₃ were co-induced in BiOI via a facile in situ assembly method at room temperature using NaBH₄ as the reducing agent. In the synthesized ternary Bi/BiOI/(BiO)₂CO₃, the oxygen vacancies, dual heterojunctions (i.e., Bi/BiOI and BiOI/(BiO)₂CO₃), and surface plasmon resonance effect of the Bi particles contributed to efficient electron-hole separation and an increase in charge carrier concentration, thus boosting the overall visible light photocatalysis efficiency. The as-prepared catalysts were applied for the removal of NO in concentrations of parts per billion from air in continuous air flow under visible light illumination. Bi/BiOI/(BiO)₂CO₃ exhibited a highly enhanced NO removal ratio of 50.7%, much higher than that of the pristine BiOI (1.2%). Density functional theory calculations and experimental results revealed that the Bi/BiOI/(BiO)₂CO₃ composites promoted the production of reactive oxygen species for photocatalytic NO oxidation. Thus, this work provides a new strategy to modify narrow-band semiconductors and explore other bismuth-containing heterostructured visible-light-driven photocatalysts.     

The Effect of pH Values on the Synthesis,Microstructure and Photocatalytic Activity of Ce‐Bi2O3 by a Two‐Step Hydrothermal Method

In this study, the effect of pH values on the microstructure and photocatalytic activity of Ce‐Bi₂O₃ under visible light irradiation was investigated in detail. In alkaline condition (e.g. pH = 9), the as‐prepared Ce‐Bi₂O₃ exhibited an agglomerated status and mesoporous structures without a long‐range order. While in weak acid condition (e.g. pH = 5), the Ce‐Bi₂O₃ exhibited a best morphology with irregular nanosheets. Correspondingly, it possessed largest surface area (24.641 m² g^?1) and pore volume (9.825E‐02 cm³ g^?1). These unique nanosheets can offer an attachment for pollutant molecules and reduce the distance of electron immigration from inner to surface, thus facilitating the separation of photoelectron and hole pairs. Compared with the pure Bi₂O₃, the band gap of Ce‐Bi₂O₃ prepared at different pH was much lower. Among them, the band gap of Ce‐Bi₂O₃ (pH of 5) was lowest (2.61 eV). Ce‐Bi₂O₃ (pH of 5) exhibited as tetragonal crystal with the bismuth oxide in the form of the composites, which could reduce the band gap width or suppress the charge‐carrier recombination, subsequently possessing great photocatalytic activity for acid orange II under visible light irradiation. After 2 h degradation under visible light, the degradation rate of acid Orange II was up to 96.44% by Ce‐Bi₂O₃ prepared at pH 5. Overall, it can be concluded that the pH values had effects on the microstructure and photocatalytic activity of Ce‐Bi₂O₃ catalysts.     

Transition metal incorporated,modified bismuth oxide (Bi2O3) nano photo catalyst for deterioration of rosaniline hydrochloride dye as resource for environmental rehabilitation

The work presented here deals with the fabrication of bare Bi₂O₃ and modified Bi₂O₃ photocatalyst. The Bi₂O₃ material was modified with selected transition metals Co²⁺, Ni²⁺ with the 1% and 3% atomic weight percent insitu doping method via co-precipitation strategy. These three catalysts were successfully utilized for the waste water purification via photocatalytic degradation route. These all fabricated materials were precisely characterized by characterization techniques such as XRD, SEM, TEM, BET, IR and UV-DRS. The characterization techniques reveal the successful synthesis of material and effective modification of bismuth oxide lattice. Since, surface area for modified Bi₂O₃ was found to be enhanced in comparison to the bare Bi₂O_3, as well as declined band gap energy for modified Bi₂O₃ clearly indicates the successful doping of Co²⁺, Ni²⁺ metals. The bare Bi₂O₃ and modified Bi₂O₃ catalyst were employed for photocatalytic degradation of cationic dye R-HCl dye. The modified Bi₂O₃ found to be excellent over degradation efficiency of R-HCl with almost 97% of dye degradation in comparison to the bare Bi₂O_3. Reactive oxygen species experiment demonstrate that the addition of isopropyl alcohol (IPA), benzoquinone (BQ) and EDTA found to be successful to quench ^.OH, O₂^.- and h⁺ in photocatalysis mechanism. Additionally, the modified Bi₂O₃ was employed for phenol molecule degradation to investigate the possible excitation of this molecule under visible light irradiation.     

Template‐Free Fabrication of Bi2O3 and (BiO)2CO3 Nanotubes and Their Application in Water Treatment

Uniform bismuth oxide (Bi₂O₃) and bismuth subcarbonate ((BiO)₂CO₃) nanotubes were successfully synthesized by a facile solvothermal method without the need for any surfactants or templates. The synergistic effect of ethylene glycol (EG) and urea played a critical role in the formation of the tubular nanostructures. These Bi₂O₃ and (BiO)₂CO₃ nanotubes exhibited excellent Cr^VI‐removal capacity. Bi₂O₃ nanotubes, with a maximum Cr^VI‐removal capacity of 79 mg g^?1, possessed high removal ability in a wide range of pH values (3–11). Moreover, Bi₂O₃ and (BiO)₂CO₃ nanotubes also displayed highly efficient photocatalytic activity for the degradation of RhB under visible‐light irradiation. This work not only demonstrates a new and facile route for the fabrication of Bi₂O₃ and (BiO)₂CO₃ nanotubes, but also provides new promising adsorbents for the removal of heavy‐metal ions and potential photocatalysts for environmental remediation.     

Highly efficient photocatalytic NO removal and in situ DRIFTS investigation on SrSn（OH）6

A novel SrSn（OH）₆ photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method.The photocatalytic activity of the SrSn（OH）₆ was evaluated by the removal of NO at ppb level under UV light irradiation.Based on the ESR measurements,SrSn（OH）₆ photocatalyst was found to have the ability to generate the main active species of O₂^·-,^·OH and ¹ O₂ during the photocatalyti...     

Structural characterization and photocatalytic properties of novel Bi<Subscript>2</Subscript>FeVO<Subscript>7</Subscript>

Bi₂FeVO₇ was prepared by a solid-state reaction technique for the first time and the structural and photocatalytic properties of Bi₂FeVO₇ were studied. The results shows that this compound crystallized in the tetragonal crystal system with space group I4/mmm. Moreover, the band gap of Bi₂FeVO₇ was estimated to be about 2.22(6) eV. For the photocatalytic water splitting reaction, H₂ or O₂ evolution was observed from pure water with Bi₂FeVO₇ as the photocatalyst by ultraviolet light irradiation. Degradation of aqueous methylene blue (MB) dye by photocatalytic way over this compound was further studied under visible light irradiation. Bi₂FeVO₇ shows higher catalytic activity compared to TiO₂ (P-25) for MB photocatalytic degradation under visible light irradiation. Complete removal of aqueous MB was realized after visible light irradiation for 170 min with Bi₂FeVO₇ as the photocatalyst. The reduction of the total organic carbon (TOC) and the formation of inorganic products, SO ₄ ²⁻ and NO ₃ ⁻ revealed the continuous mineralization of aqueous MB during the photocatalytic course.     

Retracted: Bi5O7I Nanobelts: Synthesis,Modification, and Photocatalytic Antifouling Activity

Bi₅O₇I nanobelts were prepared by a facile hydrothermal method to study the crystal phase transformation and morphology evolution. Based on these results, a crystal growth mechanism of Bi₅O₇I nanobelts was proposed. To enhance the photocatalytic antifouling activity, ethanol or TiCl₃ was used to modify the Bi₅O₇I nanobelts. The resulting BiOI/Bi₂O₂CO₃/Bi₅O₇I and TiO₂/BiOCl/Bi₅O₇I micro-nanostructures show excellent degradation activity of malachite green and bactericidal effects against Pseudomonas aeruginosa, which may be attributed to the higher charge carrier separation efficiency of these heterojunction structures. The results indicate that the formation of semiconductor composites is a very effective strategy to design high-performance photocatalyst systems.     

Untersuchungen zu Bismutseltenerdoxidhalogeniden der Zusammensetzung Bi2SEO4X (X = Cl,Br, I)

Investigations on the Bismuth Rare‐Earth Oxyhalides Bi₂REO₄X (X = Cl, Br, I) Compounds of the composition of Bi₂REO₄X (RE = Y, La–Lu; X = Cl, Br, I) have been prepared by solid state reaction of stoichiometric mixtures of BiOX, Bi₂O₃, and RE₂O₃. They were characterized by X‐ray powder diffraction, IR spectroscopy, mass spectrometry and DTA/TG measurements as well. The crystal structure (tetragonal, P4/mmm, a ≈ 3.9 Å, c ≈ 9 Å) was determined by the Rietveld method. In the structure [M₃O₄]⁺ layers are interleaved by single halogen layers. Rare‐earth and bismuth atoms in Bi₂REO₄X are 8‐coordinated. The structure can be derived from the LiBi₃O₄Cl₂ type structure. The enthalpies of formation are derived from heats of solution. The standard entropies were calculated from low‐temperature measurements of the specific heat capacities.     

Thin Coatings of α- and β-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light

Thin coatings of Bi₂O₃ were deposited on glass substrates by ultrasonic spray coating of THF solutions of the molecular precursor [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉] ⋅ 2DMSO ⋅ 7H₂O (OMc=O₂CC₃H₅) followed by hydrolysis and subsequent annealing. Depending on the synthetic protocol, the bismuth oxido cluster was transformed into either α- or β-Bi₂O₃. The as-synthesized Bi₂O₃ coatings were characterized by powder X-ray diffraction (PXRD), thickness measurements, diffuse reflectance UV-Vis spectroscopy (DRS), photoluminescence (PL) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The thin coatings (thickness: 5–16 μm) were compared with regard to their performance in photocatalytic rhodamine B (RhB) decomposition under visible light irradiation. The β-Bi₂O₃ coatings, that showed the highest photocatalytic activity, were used for the photocatalytic decomposition of other pollutants such as triclosan and ethinyl estradiol. In addition, the interplay between the photooxidation that is induced by the excitation of the catalyst using visible light and the photosensitized decomposition pathway was studied by degradation experiments of aqueous rhodamine B solutions using β-Bi₂O₃ coatings.     

In-situ construction of amorphous/crystalline contact Bi2S3/Bi4O7 heterostructures for enhanced visible-light photocatalysis

Constructing a heterojunction photocatalyst is a significant method to enhance photocatalytic activity because it can promote the separation of photogenerated carriers. Herein, amorphous/crystalline contact Bi₂S₃/Bi₄O₇ heterostructure was successfully synthesized by in-situ sulfidation of Bi₄O₇. The amorphous Bi₂S₃ is diffused on the surface of Bi₄O₇ rod, enhancing the visible light response and improving the transport of photogenerated carriers. Various characterizations confirm that the rapid separation of photogenerated carriers leads to increased photocatalytic performance. The optimized Bi₂S₃/Bi₄O₇ heterostructure photocatalyst (BiS-0.15) exhibits the highest Cr(VI) reduction (0.01350 min⁻¹) and RhB oxidation (0.08011 min⁻¹) activity, which is much higher than that of pure Bi₄O₇ and Bi₂S₃/Bi₄O₇ mixture under visible light irradiation. This work provides new insights into the construction of efficient novel photocatalysts.     

Facile Fabrication of Bi24O31Br10 Nanosheets with Phosphorus Sulfide Quantum Dots for Highly Photocatalytic Treating Organic Dyes

Herein, we report the synthesis of novel narrow band gap phosphorus sulfide quantum dots (PSQDs)-modified bismuth oxybromide (Bi₂₄O₃₁Br₁₀) heterojunction (noted as BOB/PS) for the highly efficient photo-degradation of hazardous organic pollutants including rhodamine B (RhB), methyl orange (MO), and malachite green (MG). Such a high photocatalytic activity of BOB/PSQDs heterojunction derives from the improved visible-light response capacity, high surface area/pore volume, and suitable band structure for efficient electron transfer to generate reactive oxygen species (ROS). ROS trapping experiments demonstrate that hydroxy (⋅OH) and superoxide radicals (⋅O₂⁻) play important roles in the photo-degradation. A possible S-scheme mechanism for the enhanced photocatalytic activity of BOB/PS is proposed.     

Bi@Bi2Sn2O7/TiO2等离子体复合纤维的制备及增强的光催化产氢活性

以电纺TiO_2纳米纤维为基质,采用一步水热法合成了Bi@Bi_2Sn_2O_7/TiO_2等离子体复合纤维光催化剂。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、高分辨透射电镜(HRTEM)、紫外-可见漫反射(UV-Vis DRS)和光致发光光谱(PL)等分析测试手段对样品的物相、形貌和光电性能等进行表征。以三乙醇胺为电子给体,研究了Bi@Bi_2Sn_2O_7/TiO_2复合纤维光催化裂解水制氢的反应过程。结果表明:在水热过程中,Bi_2Sn_2O_7构筑在TiO_2纳米纤维表面形成p-n结的同时,部分Bi3+被葡萄糖还原成金属Bi沉积在Bi_2Sn_2O_7上。金属Bi的等离子体共振效应与p-n结的协同作用,有效提高了样品的光催化活性,产氢速率达到7.26 mmol·h~(-1)·g~(-1)。     

Electrophysical properties of bismuth titanates with the pyrochlore structure Bi<Subscript>1.6</Subscript>M<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ti<Subscript>2</Subscript>O<Subscript>7–δ</Subscript> (M = In,Li)

Lithium-containing bismuth titanates with the pyrochlore-type structure Bi_1.6Li_xTi₂O_7–δ were obtained for the first time. The formation of the pyrochlore phase was confirmed by X-ray diffraction analysis, scanning electron microscopy and local microanalysis. In Bi_1.6M_xTi₂O_7–δ, the lithium and indium are occupied the bismuth sites, primarily. The electrophysical properties of doped bismuth titanates were studied by impedance spectroscopy in the frequency range 1–10⁶ Hz. In the low-temperature range (of up to ~400°C), electron conductivity predominates; above 400°C, the oxygen-ion type of conductivity is revealed. In the range p(O₂) = 0.21–1 atm, the average value of the sum of ion transport numbers is 0.5 at 500–550°C. The relaxation process was found from the frequency dependences of the dielectric parameters (ε', tan δ, M''), which was of the same type for systems with different dopants (In, Li) probably due to the hopping mechanism of oxygen conductivity.