Niobium Doping and Dielectric Anomalies in Bismuth Titanate

A study of the complex permittivity in bismuth titanate was conducted to reveal the nature of an anomaly in the real part of the permittivity, which occurs below the Curie temperature. This anomaly is frequency dependent and is caused by a combination of two relaxation phenomena that appear in the imaginary part of the permittivity. One of the relaxations showed classic characteristics of an ion-jump process. Niobium doping suppressed this relaxation and eliminated the nonferroelectric anomaly in permittivity. Niobium is proposed to affect the ion-jump relaxation through a decrease in the concentration and possibly the mobility of oxygen vacancies.     

Effects of Doping Trivalent Ions in Bismuth Borate Glasses

Bismuth borate glasses from the system: 40Bi₂O₃–59B₂O₃–1Tv₂O₃ (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi₂O₃–60B₂O₃, 37.5Bi₂O₃–62.5B₂O₃ and 38Bi₂O₃–60B₂O₃–2Al₂O₃ were prepared by melt quenching and characterized by density, UV-visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X-ray diffraction (XRD). Bi₃B₅O₁₂ was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare-earth ions promote the formation of metastable BiBO₃–I and BiBO₃–II phases during glass crystallization.     

钼酸铋的掺杂改性研究进展

主要介绍了稀土元素、过渡元素、C族元素、卤族元素和铋自掺杂钼酸铋的研究情况,并对钼酸铋掺杂的发展方向进行了展望。     

铋掺杂对铌酸钾钠无铅压电陶瓷结构和性能的影响

用常压烧结法制备铋掺杂铌酸钾钠无铅压电陶瓷(K0.5Na0.5)1-3xBixNbO3(KNBN)。研究不同铋掺杂量对KNN陶瓷结构、形貌、致密度及电学性能的影响。结果表明:在1 120℃烧结的含铋量为1%(摩尔分数)的陶瓷表现出最好的铁电和压电性能及较好的介电性能,即压电常数最大121pC/N,P-E回线形状达到饱和,且剩余极化为12.67μC/cm2,矫顽场Ec为13.58kV/cm,介电常数为575,损耗为5.82%(频率为1kHz)。陶瓷样品在131℃从正交结构转变到四方结构,Curie温度为400℃。     

Novel Doping Mechanism for Very-High-Permittivity Barium Titanate Ceramics

Barium titanate (BaTiO₃) can be doped with La³⁺ ions via partial substitution for Ba²⁺ ions; charge balance is maintained by the creation of Ti⁴⁺ vacancies. Samples processed in an atmosphere of 1 bar O₂ and a temperature of 1350°C are insulating and free from electronic defects associated with either O₂ loss or reduction of Ti⁴⁺ to Ti³⁺. The Curie temperature ( T _c) decreases approximately linearly as the lanthanum content increases and, at the same time, an increase in the permittivity (ɛ') maximum at T _c occurs. For the composition Ba_{1- x} La _x Ti_{1- x /4}O₃, where x = 0.05, ɛ' has a maximum value of 19000 at 18°C, compared with a typical value of 10000 at 130°C in undoped BaTiO₃ ceramics. This value is the highest value reported for A-site-doped BaTiO₃ and is linked to the mechanism of combined A-site doping and Ti-vacancy creation.     

Mechanism of Grain Orientation During Hot-Pressing of Bismuth Titanate

Grain-oriented Bi₄Ti₃O₁₂ ceramics have been prepared by hot-pressing. Platelike grains align during hot-pressing; the long-axis direction perpendicular to the crystal c axis is oriented perpendicular to the pressing direction. The effects of hotpressing conditions such as temperature, pressure, time, and type of filler on the density, orientation degree, and deformation of hot-pressed compacts were examined. Sharp increases in the density, deformation, and grain orientation occurred during the early stage; the density decreased, and the latter two incresed on prolonged hot-pressing. The grain orientation is closely related to the deformation in the radial direction. The grain-orientation mechanism is discussed referring to mechanisms proposed for high-temperature deformation in ceramics. The compact is deformed by two processes: one accompaines grain orientation, and the other does not. Grain-boundary sliding is proposed for the former process. The contribution of grain-boundary sliding to the deformation increases with increasing temperature and pressure. The filler also influences the contribution. The decrease in density is caused by cavity formation during prolonged hot-pressing.     

铋系超导体的成相过程与机制

本文考察了铋系超导体的成相过程,解释了成相机制及高价离子对成相的影响.     

Al-Sc共掺杂ZnO透明导电薄膜的掺杂机制

采用溶胶-凝胶法制备Al-Sc共掺杂ZnO透明导电薄膜,考察了结晶性、晶界状态、紫外-可见光透射光谱及Hall效应,并讨论其掺杂机制,结果表明:Sc单独掺杂时,晶粒尺寸变小,结晶性变差,晶粒表面包裹一层非晶相,透射光谱存在较大的吸收谷,无导电性;Al-Sc共掺杂时,晶粒表面无非晶相,c轴择优取向性和晶界状态变优,透射光...     

TiO_2光催化剂非金属掺杂的机理研究进展

根据国内外对TiO2光催化剂改性的研究状况,将TiO2光催化剂的改性研究分为金属离子掺杂、贵金属沉积、表面光敏化、复合半导体、非金属离子掺杂等方面.其中,非金属掺杂较其他方式的掺杂优势明显,但其机理研究不够深入.对TiO2光催化剂的各种非金属掺杂的机理研究进展进行了综述.     

TiO2光催化剂非金属掺杂的机理研究进展

根据国内外对TiO2光催化剂改性的研究状况,将TiO2光催化剂的改性研究分为金属离子掺杂、贵金属沉积、表面光敏化、复合半导体、非金属离子掺杂等方面。其中,非金属掺杂较其他方式的掺杂优势明显,但其机理研究不够深入。对TiO2光催化剂的各种非金属掺杂的机理研究进展进行了综述。     

EDTA法测定氯氧铋中铋的研究

氯氧铋作为回收金属粗铋的中间产物,其品位的高低直接影响着后面火法熔炼所产出粗铋的品位。在大量氯氧铋中铋含量的测定实践基础上,讨论了提高EDTA法测定氯氧铋中铋含量的准确度的方法。通过EDTA法测定氯氧铋精矿中铋的测定条件、干扰及消除、回收率等系统试验,拟定了以硫脲为指示剂测定铋的分析方法,该法适用性好,操作简便、准确度高,适用于中高含量铋的测定。     

Ferroelastic Toughening in Bismuth Vanadate

Bismuth vanadate has been used as a model system to examine toughening by stress-induced domain motion in a ferroelastic materials. Fracture toughnesses in the ferroelastic and paraelastic states have been compared. Toughening and R -curve behavior have been observed in the ferroelastic state. Single crystals of BiVO₄ show domain nucleation and propagation under compressive loading and domain generation during fracture. The increase in toughening in the ferroelastic state can be explained by a combination of crack deflection and domain wall motion, the latter contributing to R -curve behavior.     

EDTA法同时测定铋精矿中铋与铁的研究

对EDTA法同时测定铋精矿中铋和铁的测定条件、干扰及消除、沉淀回收率等作了系统试验,拟定了在大量铋存在下测定铁,并可同时测定铋的分析方法,该法适用性好,操作简便、准确度高,适用于各类铋精矿中铋和铁的测定。     

Bismuth electrodeposition in molten salts

The electrodeposition of bismuth from BiCl₃, Bi₂O₃ and BiOCl dissolved in chloride eutectics and borax melts has been studied. The cathodic deposition of the metal from the fused mixture KCl-LiCl-BiCl₃, at 400–600°C, and low mole fractions of BiCl₃, has been determined by a diffusion process. At higher values of the mole fraction, the discharge of ions at the cathode proceeds without polarization. The cathodic current efficiency increases with the mole fraction of the bismuth salt when temperature and cd are kept constant.In molten CaCl₂-NaCl, Bi₂O₃ appears to be slightly soluble, at 600 to 900°C. The polarization curve of a Mo electrode shows concentration polarization; the limiting cd increases with the temperature. The current efficiency is negligible at 600°C but increases considerably at higher temperature.Concentration polarization is also found in the cathodic deposition of bismuth from a BiOClBaCl₂CaCl₂-NaCl mixture at 900°C. Here, the variation of cathode current efficiency as a function of cd shows a maximum.Polarograms obtained with Mo electrodes for dilute solutions of Bi₂O₃ in molten borax, at 800–1000°C, have wave heights proportional to the concentration. At higher mole fraction the diffusion wave tends to disappear. The dependence of the current efficiency upon cd goes through a maximum at 800°C. Using Pt electrodes, polarograms can be obtained only at 800 and 900°C and 0·01 mole fraction. At larger oxide content and higher temperature there is no concentration polarization. In the same way, polarization curves with Bi electrodes show no controlling diffusion process at any mole fraction and temperature.     

Processing of Metallic Bismuth with the Production of Bismuth Oxohydroxotribromophenolate

The hydrolytic processing of metallic bismuth with the production of bismuth oxohydroxotribromophenolate pharmacopeial composition [Bi₆O₆(OH)₂](C₆H₂Br₃O)₄ used to prepare the medical drug Xeroform was studied by chemical, X-ray diffraction, and thermogravimetric analyses and electron microscopy. The results of these studies were confirmed by the industrial tests of the developed technology based on the oxidation of metallic bismuth, the dissolution of synthesized technical oxide in nitric acid, the hydrolytic purification of bismuth from impurity metals by aqueous alkaline hydrolysis with the precipitation of bismuth in the form of oxohydroxonitrate [Bi₆O₄(OH)₄](NO₃)₆?H₂O, the dissolution of bismuth oxohydroxonitrate in nitric acid, and the synthesis of bismuth oxohydroxotribromophenolate by adding an aqueous sodium tribromophenolate solution to the resulting solution in the presence of sodium acetate at a pH of 6.5–7.5 and a temperature of 90–95°C.

     

Bismuth Phosphate Glasses

Homogeneous glasses are formed in the Bi₂O₃-P₂O₅ system up to 35 mol% (63.8 wt%) Bi₂O₃. In property vs composition plots, the thermal expansion coefficient and tan δ exhibit minima, and hardness and activation energy for conduction show maxima at about 20 mol% Bi₂O₃. The deformation temperature of the glasses also increases abruptly at this composition. This anomalous behavior is interpreted in terms of a change in the function of Bi³⁺ ions from network formers to network modifiers.     

用FeCl_3从复杂铋矿中浸出金属铋

从品位低、组成复杂、伴生钼、铜矿物的复杂铋矿石中浸出金属铋,采用常规搅拌浸出法在常温常压下进行浸出,讨论了酸度、FeCl3用量、浸出时间、浸出剂用量等对铋浸出率的影响。实验结果表明:用FeCl3浸出金属铋,铋的浸出率可达95%以上。     

钒酸铋颜料

综述了钒酸铋颜料的性能、用途及其制备方法。