Ion tracks and microstructures in barium titanate irradiated with swift heavy ions: A combined experimental and computational study

Tetragonally structured barium titanate (BaTiO₃) single crystals were irradiated using 635 MeV ²³⁸U⁺ ions to fluences of 1 × 10⁷, 5 × 10¹⁰ and 1.4 × 10¹² ions cm^?2 at room temperature. Irradiated samples were characterized using ion channeling, X-ray diffraction, helium ion microscopy and transmission electron microscopy. The results show that the ion-entry spot on the surface has an amorphous core of up to ～10 nm in diameter, surrounded by a strained lattice structure. Satellite-like defects around smaller cores are also observed and are attributed to the imperfect epitaxial recrystallization of thermal-spike-induced amorphization. The critical value of the electronic stopping power for creating observable amorphous cores is determined to be ～22 keV nm^?1. Molecular dynamics simulations show an amorphous track of ～1.2 nm in radius under thermal energy deposition at 5 keV nm^?1; the radius increases to ～4.5 nm at 20 keV nm^?1. A linear fit of the core diameter as a function of the square root of the energy deposition rate suggests a reduction in the diameter by an average of ～8.4 nm due to thermal recrystallization if electron–phonon coupling efficiency of 100% is assumed. The simulation also reveals details of the bonding environments and shows different densities of the amorphous zones produced at different energy deposition rates.     

Structure, dielectric and electrical properties of cerium doped barium zirconium titanate ceramics

Rare-earth doped barium zirconium titanate (BZT) ceramics, Ba(Zr_0.25Ti_0.75)O₃ + xCeO₂, (x = 0-1.5 at%) were obtained by a solid state reaction route. Perovskite-like single-phase compounds were confirmed from X-ray diffraction data and the lattice parameters were refined by the Rietveld method. It is found that, integrating with the lattice parameters and the distortion of crystal lattice, there is an alternation of substitution preference of cerium ions for the host cations in perovskite lattice. Morphological analysis on sintered samples by scanning electron microscopy shows that the addition of rare-earth ions affects the growth of the grain and remarkably changes the grain morphology. The effect of rare-earth addition to BZT on dielectric and electrical properties is analyzed. High values of dielectric tunability are obtained for cerium doped BZT. Especially, the experimental results on the effect of the contents of rare-earth addition on the resistivity of BZT ceramics were investigated, demonstrating that the samples with x = 0.4 and x = 0.6 could be semiconducting in air atmosphere.     

粉末-凝胶法制备铌酸锶钡/钛酸锶钡陶瓷及其表征(英文)

钛酸锶钡(SrxBa1-xTiO3, BST)和铌酸锶钡(SrxBa1-xNb2O6, 0.25≤x≤0.75, SBN)是重要的铁电材料,具有优良的热电、介电和红外快速响应性能。使用廉价的 Nb2O5粉末,应用粉末-溶胶工艺合成铌酸锶钡/钛酸锶钡复相陶瓷(SBN/SBT)。XRD 结果表明:钨青铜相和钙钛矿相共存于体系之中。复相陶瓷形成过程中形成了 TiO2、BaNb2O6(BN)、SrNb2O6(SN)等中间相。干凝胶在800°C下预烧3h,X射线光电子能谱(XPS)分析表明,随着体系组分的变化,Ti元素只存在+4价的化合态,而Nb元素的价态和体系的组分有关。     

Mg-10Li-1Zn合金锡酸盐转化膜的制备及其耐蚀性能研究

采用含有锡酸钠和磷酸二氢钾两种成分的转化液,在Mg-10Li-1Zn合金表面上得到锡酸盐化学转化膜,研究了该转化膜的微观结构、成膜机制及抗腐蚀性能。结果表明,此膜层均匀、连续,主要由MgSnO3、Mg3（PO4）2和SnO组成。腐蚀试验结果显示,该转化膜改善了基体合金的抗腐蚀能力。     

Preparation and performance of titanate nanotube by hydrothermal treatment

Titanate nanotubes were synthesized by hydrothermal treatment in concentrated NaOH solution followed by HCl washing. The as-prepared nanotubes were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and N2 adsorption-desorption isotherm measurements （BET）. The results displayed that the hydrothermal treatment temperature within 110-160℃ not only affected the structure of the nanotube, but also the anatase-to-rutile transformation temperature. The nanotube could be obtained only in an appropriate concentration of NaOH solution. The diameter of the nanotube was 6-10 nm. The surface area of the product initially increased with increasing treatment temperature, to reach a maximum of about 630 m^2/g at 130℃, and then decreased with a further increase in temperature.     

Ba（Sn0．1Ti0．9）O3粉体的熔盐法制备与性质

采用熔盐法研究了Ba（Sn0．1Ti0．9）O3铁电体粉体的制备工艺和粉体性质。探讨了在熔盐催化下，合成温度对Ba（Sn0．1Ti0．9）O3反应完全程度及粉体形态的影响。结果表明，当反应温度达到900℃时，在熔盐环境下即可合成单相固体Ba（Sn0．1Ti0．9）O3，随着反应温度提高，粉体尺寸变化不大，但当温度超过950℃时出现晶粒异常长大趋势。烧结陶瓷的形貌和介电性质显示陶瓷粉体烧结活性好且介电性质优良。     

Structural, compositional and electrical properties of co-precipitated zinc stannate

Zinc stannate (Zn₂SnO₄) powders were synthesized by chemical co-precipitation method using stannic chloride pentahydrate (SnCl₄·5H₂O) and zinc acetate (Zn(CH₃COO)₃·4H₂O) as precursors in aqueous medium. The influence of sintering temperatures on the structural, compositional, dielectric, electrical and impedance properties has been studied. X-ray diffraction study reveals that samples sintered at 400-1200 °C show combined phases viz. ZnO, SnO₂, Zn₂SnO₄. The observed binding energies of Sn 3d_5/2, Zn 2p_3/2 and O 1s reveal that Sn and Zn are present in oxidized state (Sn-O-Zn). We studied interparticle interactions like grains, grain boundary effects using complex impedance spectroscopy.     

Dielectric properties and point defect behavior of antimony oxide doped Ti deficient barium strontium titanate ceramics

The microstructures and dielectric properties of Sb₂O₃-doped Ti deficient barium strontium titanate ceramics prepared by solid state method were investigated with non-stoichiometric level and Sb₂O₃ content by SEM, XRD and LCR measure system. It is found that with the increase of δ, (Ba_0.75Sr_0.25)Ti_1–δO_3–2δ ceramics transform from single phase solid solutions with typical cubic perovskite structure to multiphase compounds while (Ba_0.75Sr_0.25)Ti_0.998O_2.996 ceramics remain to be single-phase with the increasing Sb₂O₃ content. The distortion of the ABO₃ perovskite lattice caused by V_Ti″″ and V_o^?? induces the drop of Curie temperature and the rise of relative dielectric constant in (Ba_0.75Sr_0.25)Ti_1–δO_3–2δ ceramics with increasing δ value. The orientation of V_o^?? elastic dipoles results in the domain-wall pinning and thus the reduction of the dielectric loss. With increasing Sb₂O₃ content, the relative dielectric constant, dielectric constant maximum and Curie temperature of (Ba_0.75Sr_0.25)Ti_0.998O_2.996 ceramics decrease dramatically while the dielectric loss increases.     

镍-磷-钛酸钾晶须化学复合镀层的制备及性能

采用化学复合镀方法制备镍-磷-钛酸钾晶须复合镀层,用扫描电镜和金相显微镜观察复合镀层的表面形貌和断面结构,用XRD研究时效温度对镀层组织结构的影响,并解释时效温度对镀层显微硬度的影响机制。采用交流阻抗技术和中性盐雾实验研究镀层的耐腐蚀性能。在销-盘式摩擦磨损试验机上进行复合镀层的摩擦磨损性能测试。结果表明：镀层的显微硬度随温度的变化曲线呈单峰形态,在400℃时达到最大值;复合镀层具有良好的耐腐蚀性能和摩擦磨损性能,在同等实验条件下,复合镀层的磨损率只有Ni-P镀层的1/4。     

Structural and optical characterization of BaSnO3 nanopowder synthesized through a novel combustion technique

Nanocrystalline Barium stannate (BaSnO₃) was synthesized through auto-ignited combustion technique. The X-ray diffraction studies of BaSnO₃ nanoparticles reveals that the nanopowder is single phase, crystalline, and has a cubic perovskite structure with a lattice constant a = 4.115 Å. The average particle size calculated from full width half maximum (FWHM) using Scherer formula is ∼25 nm. The phase purity of the powder was further examined using Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopic techniques. XRD pattern of BaSnO₃ was refined for atomic coordinates, lattice parameters and occupancies using Rietveld analysis. Vibrational analysis of sample shows that there is a phase transition from distorted cubic to ideal cubic structure during heat treatment. The thermal stability of BaSnO₃ nanopowder has been confirmed using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The particle size of the as-prepared powder from transmission electron microscopy was found to be in the range 20-30 nm. The absorption spectra and photoluminescence spectra of the sample were also studied. The band gap determined was 2.887 eV and found to be a semiconductor.     

钛酸钾晶须/聚丙烯导热抗静电复合材料的制备与性能

采用热压成型工艺制备了导电钛酸钾晶须(PTWs)/聚丙烯(PP)复合材料,研究了晶须用量对复合材料导热性能、抗静电性能和力学性能的影响。结果表明,随着PTWs用量的增加,PTWs/PP复合材料的热导率提高、体积电阻率和摩擦静电荷下降;材料的拉伸强度、弯曲强度均随PTWs用量的增加呈先增大后减小的趋势;而熔体流动速率则呈增大趋势。当PTWs体积分数达到0.38%时,材料的热导率达到最大值0.5105 W.m-1.K-1,电阻率降低到109Ω.cm以下,满足一般抗静电材料的要求。     

锆钛酸铅压电陶瓷的流延法制备及其性能

流延法工艺具有工艺便捷、尺寸可调、成膜质量好等优势。采用流延法制备PZT压电陶瓷,通过扫描电子显微镜观察压电陶瓷微观形貌,通过准静态d33测量仪测试压电陶瓷的压电应变常数d33。探究粉末粒径以及流延工艺参数包括刮刀高度、流延速度、热压压力等对PZT压电陶瓷性能的影响,获得的PZT压电陶瓷其压电应变常数d33最高可达454 pC/N,致密度最高可达97.68%。该方法适用于制备大尺寸压电器件。     

锂离子电池极材料钽掺杂钛酸锂的制备及电化学性能

通过固相合成制备了钽掺杂材料Li4Ti4.95Ta0.05O12。通过XRD和SEM来表征Li4Ti4.95Ta0.05O12的结构和形貌。钽掺杂并没有改变本体材料的结构和形貌,而且显著提高了材料的循环性能和倍率性能。Li4Ti4.95Ta0.05O12在10C和30C倍率时的放电容量分别是116.1mA.h/g和91.0mA.h/g。Ta掺杂取代了Li4Ti5O12中的Ti的位置,产生了Ti4＋/Ti3＋混合价态,从而提高了钛酸锂的电导率。故具有优异的高倍率性能,是一种优异的锂离子电池负极材料。.     

Correlation between nanostructural and electrical properties of barium titanate-based glass-ceramic nano-composites

Glasses in the system BaTiO₃-V₂O₅-Bi₂O₃ have been transformed into glass-ceramic nano-composites by annealing at crystallization temperature T_cr determined from DSC thermograms. After annealing they consist of small crystallites embedded in glassy matrix. The crystallization temperature T_cr increases with increasing BaTiO₃ content. XRD and TEM of the glass-ceramic nano-composites show that nanocrystals were embedded in the glassy matrix with an average grain size of 25 nm. The resulting materials exhibit much higher electrical conductivity than the initial glasses. It was postulated that the major role in the conductivity enhancement of these nanomaterials is played by the developed interfacial regions between crystalline and amorphous phases, in which the concentration of V⁴⁺-V⁵⁺ pairs responsible for electron hopping, has higher than values that inside the glassy matrix. The experimental results were discussed in terms of a model proposed in this work and based on a “core-shell” concept. From the best fits, reasonable values of various small polaron hopping (SPH) parameters were obtained. The conduction was attributed to non-adiabatic hopping of small polaron.     

Dielectric and ferroelectric properties and electric conductivity of sol-gel derived PBZT ceramics

(Pb_1−xBa_x)(Zr_1−yTi_y)O₃ (PBZT) is a solid solution in which ferroelectric, relaxor or antiferroelectric properties are observed depending on composition. The substitution of Ba²⁺ into A position of the perovskite structure leads to the decrease in phase transition temperature and it gradually leads to relaxor properties. The majority of papers describe PBZT obtained from oxides. We report the results of the investigation of the properties and phase transitions of (Pb_1−xBa_x)(Zr_0.65Ti_0.35)O₃ ceramics with x = 0.09, 0.25 and 0.35 obtained by the sol-gel method with final free sintering (FS) at 1573 K/4 h and by the hot pressing (HP) method at 1473 K/2 h/20 MPa. Unlike pure PZT, the properties of HP-PBZT samples obtained at lower (1473 K) temperature are a little inferior than FS samples. It is probably related to the fact that barium requires higher final sintering temperatures.We present the results of XRD and dielectric measurements vs. temperature for PBZT ceramics. On the basis of dielectric measurements a.c. conductivity and activation energies have been calculated. In agreement with earlier literature data, we note that with the increasing Ba content T_m decreases and the maximum of ?(T) is wider. However, we do not observe a shift of T_m with increasing frequency. The room P(E) hysteresis loops become more narrow and the polarization is smaller. The increase in dielectric losses with increasing temperature makes the measurement of hysteresis loops at low frequencies and high temperatures difficult.     

Investigation of physicochemical transformation at mechanochemical, hydrothermal and microwave treatment of barium titanyloxalate

The effect of mechanochemical (in air and water) as well as hydrothermal and microwave treatment on physicochemical transformations of barium titanyloxalate was studied. The samples were examined using XRD and thermal analysis, FTIR spectroscopy, argon thermodesorption and granulometry. Barium metatitanate is already formed during mechanochemical treatment of barium titanyloxalate in air atmosphere and the following thermal treatment at 550 °C improves its crystal structure. At the same time barium metatitanate is only formed at 800 °C in the case of usual thermal decomposition of barium titanyloxalate.Hydrothermal and microwave treatment of barium titanyloxalate promotes formation of the barium orthotitanate (Ba₂TiO₄) and barium carbonate (BaCO₃) mixture.     

Preparation and properties of the barium borate glassy matrix composite materials containing fused silica and monoclinic zirconia

In this work, the LTCC composite materials containing fused silica and monoclinic zirconia ceramic particles, respectively, which based on the composite matrix composed of the barium borate glassy matrix and α-alumina ceramic particles, were prepared by traditional solid-state preparation process at a sintering temperature of 900 °C. Sintering mechanism and physical properties, e.g. dielectric properties and coefficient of thermal expansion (CTE), of the LTCC composite ceramics are investigated and discussed in detail in terms of their mineral phase composition. The results indicate that a barium borate glassy phase can be easily formed from a barium borate compound, which is obtained by the chemical combination of barium hydroxide octahydrate and an aqueous solution of boric acid, at a sintering temperature of 900 °C. In turn, the barium borate glassy melts can supply a liquid phase sintering aid for the fabrication of the LTCC composite ceramics with the sintering temperature of 900 °C during sintering. The introduction of the α-alumina ceramic particles to the barium borate glassy matrix can improve the sintering behavior whereas the presence of fused silica or monoclinic zirconia particles in the composite ceramics is important to adjust the dielectric, thermal and mechanical properties of the LTCC composite materials. The work may be referenced for the fabrication of multi-layer LTCC structures with tailored physical properties.     

Synthesis and characterization of metastable Ag-B solid solutions

1　INTRODUCTIONMechanicalalloying (MA) [1] hasbecomeawide lyusedtechniquetosynthesizeavarietyofmaterials ,suchasamorphousalloys ,nanocrystallinematerials ,compounds ,solidsolutionsandsoforth .Especially ,theformationofnonequilibriummaterialscomposedofimmiscibleelementsbyMAhasreceivedincreasedattention .Anumberofbinarysystemshavebeenin vestigated ,includingAg Cu[2 4 ] ,Ag Fe[5] ,Fe Cu[6 ] ,Ag Ni[7] andothers .Comparisonwithothersynthesismethods ,suchasrapidlyquenching ,MAhasadvantages…     

Fabrication and electrical characterization of 15% yttrium-doped barium zirconate—nitrate freeze drying method combined with vacuum heating

We applied a nitrate freeze-drying method to obtain a fine synthesized powder of 15% yttrium-doped barium zirconate. Fine 15% yttrium-doped barium zirconate powder of particle size about 30 nm was obtained by synthesizing at 500 °C in vacuum from a powder mixed by the nitrate freeze-drying method. However, we could not obtain such fine powder by synthesizing in air. Using the powder synthesized in vacuum, large and homogeneous grains of 15% yttrium-doped barium zirconate were easily obtained after sintering. Then, the bulk and grain boundary resistance were evaluated by AC 2-terminal measurement of sample in the form of bar and pellet and DC 4-terminal measurement of bar-shape sample. The grain boundary resistance was not inversely proportional to the grain size as theoretically expected. We concluded that specific grain boundary conductivity varies with samples. Some impurities, evaporation loss of barium oxide and/or other unexpected reasons might affect the grain boundary resistance in 15% yttrium-doped barium zirconate.     

草酸镍钴固溶体的制备与鉴别

以可溶性氯化镍、氯化钴和草酸或草酸铵为原料,氨水为pH值调节剂,采用液相共沉淀法合成草酸镍钴共沉淀产物,借助X射线衍射(XRD)、热重-差热分析(TG-DTA)和扫描电镜(SEM)对共沉淀产物进行表征,并将结果与机械混合物进行比较.结果表明:在共沉淀过程中,当溶液pH≤5.0时,钴离子易进入草酸镍晶格中形成置换固溶体,得到的共沉淀产物为草酸镍钴单相固溶体,其热分解行为明显不同于具有相同配比的机械混合物;当pH＞5.0时,镍离子和钴离子与草酸根离子的共沉淀过程为分步沉淀,得到的共沉淀产物为组分分布均匀的复杂混合物,而非单相固溶体.