Synthesis and structural characterization of (Bi2O3)1?x (Y2O3)x and (Bi2O3)1?x (Gd2O3)x solid solutions

Solid solution series, (Bi₂O₃)_1−x (Y₂O₃)_x and (Bi₂O₃)_1−x (Gd₂O₃)_x, forx = 0.10, 0.20, 0.30 and 0.40 were synthesized by standard ceramic technique. The structural phase characterization was carried out using X-ray powder diffraction technique. It was found that the solid solution containing 20–40 mole% of Y₂O₃ had face-centred cubic structure. All samples of the solid solution series, (Bi₂O₃)_1−x (Gd₂O₃)_x, had rhombohedral single phase in the concentration range 0.10 ≤x ≤ 0.40. Lattice parameters offcc phase of Y₂O₃ doped samples were calculated from the X-ray diffraction data. The lattice constant ‘a’ gradually decreases with increasing content of dopant concentration (x) for the Y₂O₃ doped system and obeys Vegard’s rule. The unit cell parameters for the (Bi₂O₃)_1−x (Gd₂O₃)_x doped samples showing rhombohedral phase were obtained on hexagonal setting.     

Surface and bulk properties of Cu nanocluster composites in LiNbO3

Implantation of 60 keV Cu⁻ ions into LiNbO₃ resulted in formation of complex nanocomposites consisting of metal Cu nanoparticles distributed among nanodomains of the host medium. The nanodomains of the host medium correspond to regions of a few hundred naometers in diameter with a constant refractive index. Distributions of the Cu nanoparticles and nanodomains in the implanted region do not correlate with each other. Variations of linear and non-linear optical absorption of the nanocomposites are mainly determined by the change of chemical composition and structure of implanted regions of LiNbO₃.     

Optical properties of Sm doped Mg:LiNbO3 and Zn:LiNbO3 single crystals

Sm³⁺ doped Mg:LiNbO₃ and Zn:LiNbO₃ are grown by Czochralski method. Optical transmittance and emission spectra are measured and Judd-Ofelt theory is applied to determine phenomenological intensity parameters, oscillator strengths, radiant transition rates, total radiant lifetimes, and branching ratios. The calculations show that Judd-Ofelt parameters with the relation of Ω₄ > Ω₂ > Ω₆ exist, and ΣΩ_ξ (ξ = 2, 4 and 6) in Sm:Zn:LiNbO₃ decreases. Fluorescence spectra indicate that visible fluorescence of Sm³⁺ is made up of 570, 606, 613 and 654 nm emission bands in these crystals under 409 nm excitation.     

Microstructure and wear properties of laser melted γ-Ni/Mo2Ni3Si metal silicide “in situ” composite

Wear resistant γ/Mo₂Ni₃Si metal silicide “in situ” composite consisting of Mo₂Ni₃Si primary phase and lamellar γ/Mo₂Ni₃Si eutectics was fabricated by the laser melting process. The γ/Mo₂Ni₃Si composite has an excellent wear resistance under metallic dry sliding wear test conditions mating with hardened 1.0% C-1.5% Cr bearing steel. The excellent tribological properties are attributed to the high hardness of Mo₂Ni₃Si and the toughening effect of the ductile γ solid solution. Wear of the γ/Mo₂Ni₃Si composite is governed by the micro-cracking and spalling of the dendritic Mo₂Ni₃Si primary phase and the preferential wear of the interdendritic γ/Mo₂Ni₃Si eutectics.     

Synthesis and spectral properties of Ce[Ag(CN)2]3

Cerium ion luminescence in crystalline hosts forms the basis of many blue phosphor and scintillator technologies. We report the synthesis of luminescent single crystals of cerium dicyanoargentate. The luminescence properties are characterized using both steady-state and time-resolved spectroscopy. The broad, overlapping dicyanoargentate and Ce³⁺ emissions are decomposed into three Gaussians, revealing the characteristic dicyanoargentate emission at 350 nm while the Ce³⁺ 5d–4f transitions are observed at 359 nm and 391 nm. Excitation measurements show that the 4f–5d Ce³⁺ absorption overlaps the 320 nm emission of the dicyanoargentate ions, leading to a strong coupling between the dicyanoargentate energy donors and Ce³⁺ acceptors. We conclude that the cerium is excited through an energy transfer process from the dicyanoargentate species, resulting in strong room temperature luminescence.     

复合氧化物Ln0.67Sr0.33MnO_3(Ln=La、Pr、Nd、Sm)的制备、结构与电性

本文通过共沉淀工艺会成了复合氧化物Ln_0.67Sr_0.33MnO₃(Ln=La、Pr、Nd、Sm）与传统陶瓷制各方法相比，成相温度降低约450℃．经X射线衍射分析表明，所得复合氧化物为立方钙钛矿结构，晶胞参数随稀土离子半径变化而呈规律性变化．样品的四极法电阻率测试结果表明：样品中的稀土离子Ln的离子半径对其本身的导电性起决定性的作用．应用双交换理论，只能部分地解释该实验结果．由此推测稀土离子中的4f层电子在电导过程中起一定作用．     

LiNi0.8Co0.15Al0.05O2/石墨锂离子电池高荷电存储老化机理研究

高荷电存储寿命对锂离子电池的使用性能具有重要影响, 但是相关研究却较为缺乏。本研究通过高温加速实验, 研究了LiNi_0.8Co_0.15Al_0.05O₂(NCA)/石墨锂离子电池在55 ℃下的存储寿命, 分析了正负极材料在电池寿命终点时的电化学性能和界面变化。研究结果表明, 在55 ℃、高荷电状态下NCA/石墨锂离子电池的存储寿命约为90 d。在寿命终点时, 正负极活性材料的容量有一定下降, 但不是电池容量衰减的主要原因。界面分析表明, 存储后负极表面固体电解质界面(SEI)膜增长明显, 而正极表面固体电解质界面(PEI)膜无明显变化。SEI膜的增长主要是由于电解液溶剂和锂反应, 造成石墨内锂损失, 使电池内可循环锂减少, 这是NCA/石墨电池在存储过程中容量损失的主要原因。     

Role of La0.5Sr0.5CoO3 template layers on dielectric and electrical properties of pulsed-laser ablated Pb(Nb2/3Mg1/3)O3-PbTiO3 thin films

Relaxor ferroelectric thin films of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) deposited on platinized silicon substrates with and without template layers were studied. Perovskite phase (80% by volume) was obtained through proper selection of the processing conditions on bare Pt/Ti/SiO₂/Si substrates. The films were initially grown at 300 °C using pulsed-laser ablation and subsequently annealed in a rapid thermal annealing furnace in the temperature range of 750-850 °C to induce crystallization. Comparison of microstructure of the films annealed at different temperatures showed change in perovskite phase formation and grain size etc. Results from compositional analysis of the films revealed that the films initially possessed high content of lead percentage, which subsequently decreased after annealing at temperature 750-850 °C. Films with highest perovskite content were found to form at 820-840 °C on Pt substrates where the Pb content was near stoichiometric. Further improvement in the formation of perovskite PMN-PT phase was obtained by using buffer layers of La_0.5Sr_0.5CoO₃ (LSCO) on the Pt substrate. This resulted 100% perovskite phase formation in the films deposited at 650 °C. Dielectric studies on the PMN-PT films with LSCO template layers showed high values of relative dielectric constant (3800) with a loss factor (tan δ) of 0.035 at a frequency of 1 kHz at room temperature.     

Electrical and optical properties of (Pb0.9La0.1)TiO3 films prepared by the sol–gel method with ultrasound application

(Pb_0.9La_0.1)TiO₃ thin films were deposited onto indium tin oxide-coated glass and Pt/Ti/SiO₂/Si substrates by spin coating. One set of the solutions was sonication-treated during the sol preparation, while the other remained untreated for comparison. The results were analyzed in terms of perovskite developments, dielectric constants and losses, polarization behavior, and optical properties. Perovskite formation temperatures became lower by application of the sonication process. Furthermore, dielectric/ferroelectric and optical transmittance properties were improved substantially.     

Electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics modified with WO3

Ferroelectrics 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) + x mol% WO₃ (x=0.1, 0.5, 1, 2) were prepared by columbite precursor method. Electrical properties of WO₃-modified ferroelectrics were investigated. X-ray diffraction (XRD) was used to identify crystal structure, and pyrochlore phase were observed in 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃+2 mol% WO₃. Dielectric peak temperature decreased with WO₃ doping, indicating that W⁶⁺ incorporated into PMN-PT lattice. Lattice constant, pyrochlore phase and grain size contribute to the variation of K_max. Both piezoelectric constant (d₃₃) and electromechanical coupling factors (k_p) were enhanced by doping 0.1 mol% WO₃, which results from the introduction of “soft” characteristics into PMN-PT, while further WO₃ addition was detrimental. We consider that the two factors, introduction of “soft” characteristics and the formation of pyrochlore phase, appear to act together to cause the variation of piezoelectric properties of 0.67PMN-0.33PT ceramics doping with WO₃.     

Ionic conductivity of a gel polymer electrolyte based on Mg(ClO4)2 and polyacrylonitrile (PAN)

Magnesium ion containing gel polymer electrolytes based on polyacrylonitrile (PAN) have been synthesized and characterized using ac impedance measurements. The electrolyte composition having the highest room temperature conductivity was found by varying the ratios propylene carbonate/ethylene carbonate (PC/EC) and PAN/Mg(ClO₄)₂. The corresponding composition was 18 mol% PAN:64 mol% EC:14 mol% PC:4 mol% Mg(ClO₄)₂. The ac conductivity measurements were carried out from room temperature upto 70 °C with blocking (stainless steel) electrodes. The room temperature conductivity is 3.2×10⁻³ S cm⁻¹ and the activation energy is 0.24 eV over the temperature range used. The high conductivity and the low activation energy of the material could possibly be due to the liquid electrolyte, Mg(ClO₄)₂ in EC/PC trapped in a matrix of PAN, as suggested by previous workers. According to dc polarization measurements, the gel electrolyte appears to be predominantly an anionic conductor.     

Electrical properties of glasses in the Na2O–MoO3–P2O5 system

A range of coloured electronic or mixed ionic–electronic glasses has been evidenced in the Na₂O–MoO₃–P₂O₅ system. The properties of these glasses have been studied along different composition lines corresponding either to a fixed Na₂O content or a constant Mo/P ratio. An EPR spectroscopy investigation of these glasses has allowed to determine the Mo⁵⁺ ion percentages in these materials. The electrical properties of these glasses have been studied by impedance spectroscopy, and the electronic and ionic contributions have been evaluated. The properties of these sodium glasses have been compared with those of lithium glasses with the same compositions.     

Magnetic field induced ferroelectric and dielectric properties in Pb(Zr0.5Ti0.5)O3 films containing Fe3O4 nanoparticles

About 1.05 µm-thick Pb(Zr_0.5Ti_0.5)O₃ (PZT) films containing Fe₃O₄ nanoparticles were deposited on LaNiO₃-coated silicon substrates through a sol-gel technique. Fe₃O₄ nanoparticles were effectively dispersed into PZT solution under the involvement of polyvinylpyrrolidone. X-ray diffraction confirmed the coexistence of PZT and Fe₃O₄ phases without other impurity phases. Scanning electron microscope revealed that the thick composite films possess well-defined and crack-free microstructure. The composite films exhibit good ferroelectric and ferromagnetic properties at room temperature. An obvious magnetodielectric effect has been demonstrated in the Pb(Zr_0.5Ti_0.5)O₃/Fe₃O₄ composite films. Magnetic field induced change in ferroelectric polarization loop may support the possible magnetoelectric coupling between PZT and Fe₃O₄ phases.     

单晶铌酸锂薄膜光波导的制备研究

为了优化单晶铌酸锂薄膜光波导的性能,研究了基于单晶铌酸锂薄膜材料的光波导刻蚀工艺。虽然Ar⁺物理刻蚀能够达到最高95 nm/min的刻蚀速率,但难以获得光滑的波导侧壁,且以Cr作为掩膜的刻蚀选择比为1∶1,这意味着较差的选择性使其难以实现铌酸锂的深刻蚀。而采用反应离子刻蚀(RIE)得到的刻蚀速率较低,但是以Cr作为掩膜的刻蚀选择比能够达到6∶1以上,同时能够获得光滑、陡直的侧壁形貌。最终在450 nm厚度的单晶铌酸锂薄膜上,采用RIE制备了宽度为4μm、高度为370 nm的脊型光波导,并以端面耦合的方法进行测试,得到该波导的传输损耗约为5.2 dB/cm。     

Interfacial characteristics and dielectric properties of Ba0.65Sr0.35TiO3 thin films

Ba_0.65Sr_0.35TiO₃ (BST) thin films were deposited on Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) depth profiling data show that each element component of the BST film possesses a uniform distribution from the outermost surface to subsurface, but obvious Ti-rich is present to BST/Pt interface because Ti⁴⁺ cations are partially reduced to form amorphous oxides such as TiO_x (x < 2). Based on the measurement of XPS valence band spectrum, an energy band diagram in the vicinity of BST/Pt interface is proposed. Dielectric property measurements at 1 MHz reveal that dielectric constant and loss tangent are 323 and 0.0095 with no bias, while 260 and 0.0284 with direct current bias of 25 V; furthermore, tunability and figure of merit are calculated to be 19.51% and 20.54, respectively. The leakage current density through the BST film is about 8.96 × 10^− 7 A/cm² at 1.23 V and lower than 5.66 × 10^− 6 A/cm² at 2.05 V as well as breakdown strength is above 3.01 × 10⁵ V/cm.     

An investigation on electrochromic properties of (WO3)1−x-(Fe2O3)x thin films

In this research, the effect of Fe₂O₃ content on the electrochromic properties of WO₃ in thermally evaporated (WO₃)_1−x-(Fe₂O₃)_x thin films (0 ≤ x ≤ 0.4) has been studied. The atomic composition of the deposited metal oxides was determined by X-ray photoelectron spectroscopy analysis. The surface morphology of the thin films has been examined by atomic force microscopy. The surface roughness of all the films was measured about 1.3 nm with an average lateral grain size of 30 nm showing a smooth and nanostructured surface. The electrochromic properties of (WO₃)_1−x-(Fe₂O₃)_x thin films deposited on ITO/glass substrate were studied in a LiClO₄ + PC electrolyte by using ultraviolet-visible spectrophotometry. It was shown that increasing the Fe₂O₃ content leads to reduction of the optical density (ΔOD) of the colored films and also leads to increasing the optimum coloring voltage from 4 to 6 V in which ΔOD shows its maximum values, in our experimental conditions. Furthermore, by using this procedure, it is possible to make an electrochromical filter which behaves similar to the colored WO₃ film in the visible region, while it can be nearly transparent for near-infrared wavelengths, in contrast of the pure colored WO₃ film.     

Y3+掺杂Li4Ti5O12负极材料的电荷输运特性及电化学性能研究

以Li₂CO₃与锐钛矿型TiO₂为原料,六水合硝酸钇（Y（NO₃）₃·6H₂O）为钇源,采用球磨辅助固相法合成了Li₄Ti_5-xY_xO₁₂（x=0,0.05,0.10,0.15,0.20）负极材料。通过X射线衍射分析（XRD）、扫描电镜（SEM）、能谱仪（EDS）与X射线光电子能谱（XPS）分别对材料的物相与形貌进行表征分析,并利用电化学工作站对材料的电化学性能与电荷输运特性进行测试。结果表明,Y³⁺掺杂没有影响尖晶石型Li₄Ti₅O₁₂（LTO）材料的尖晶石结构,x=0.15时,Li₄Ti_4.85Y_0.15O₁₂样品的离子与电子电导率分别为2.68×10^-7 S·cm^-1和1.49×10^-9 S·cm^-1,比本征材料提升了1个数量级,表现出良好的电荷输运特性。电化学测试表明,Li₄Ti_4.85Y_0.15O₁₂样品在0.1 C倍率首次放电比容量可达171 mAh·g^-1,且在10 C与20 C高倍率下仍然拥有102 mAh·g^-1和79 mAh·g^-1的较高比容量,循环200周次后容量保持率分别为92.6%和89.1%,表现出良好的倍率特性。     

Phase developments in the Pb(Zn1/2W1/2)O3-Pb(Zn1/3Ta2/3)O3-Pb(Zn1/3Nb2/3)O3 pseudo-ternary system

The phase stability ranges in the B-site precursor (Zn_1/2W_1/2)O₂-(Zn_1/3Ta_2/3)O₂-(Zn_1/3Nb_2/3)O₂ were determined by X-ray diffraction (XRD), where wolframite, tri-αPbO₂, and columbite phases were identified. Next attempts were carried out (with the addition of PbO) for the system Pb(Zn_1/2W_1/2)O₃-Pb(Zn_1/3Ta_2/3)O₃-Pb(Zn_1/3Nb_2/3)O₃, where the perovskite phase did not develop in the entire compositions investigated. Instead, only the Pb₂WO₅ and pyrochlore phases (along with ZnO) resulted.     

Electrical properties tailoring in Ni-particle-dispersed (Ba0.95Ca0.05)(Ti0.96Zr0.04)O3 composites

Ni-particle-dispersed (Ba_0.95Ca_0.05)(Ti_0.96Zr_0.04)O₃ (BCTZ/Ni) piezoceramic composites were prepared via sintering at 1300 °C in industrial N₂ gas. Structural characterizations showed that the metallic Ni was not oxidized and the BCTZ preserved the perovskite structure. The Ni particles were uniformly distributed in the BCTZ ceramic matrix. The relative dielectric constant ?_r of the BCTZ/Ni composites increased from 1362 to 3910 with increasing Ni content from 0 to 20 vol.%, which is explained by the Maxwell equation as well as the micro-capacitor model. The percolation theory of insulator–metal transitions is also applied to correlate the rapid increase of dielectric constant with Ni content. The piezoelectric constant d₃₃ gradually decreased from 230 to 50 pC N⁻¹, giving a gradient profile of piezoelectric property. We demonstrate that the electrical properties can be effectively tailored by dispersing metal particles into piezoceramics.     

Microstructure, domain structures and ferroelectric properties in (Pb0.8,La0.1,Ca0.1)TiO3/Pb(Zr0.2,Ti0.8)O3 bilayered thin film

Ferroelectric (Pb_0.8,La_0.1,Ca_0.1)TiO₃/Pb(Zr_0.2,Ti_0.8)O₃ (PLCT/PZT) bilayered thin film was prepared on Pt(111)/Ti/SiO₂/Si(100) substrate by RF magnetron sputtering technique. Pure perovskite crystalline phase, determined by X-ray diffraction, was formed in the PLCT/PZT bilayer. The bilayered film exhibited a very dense and smooth surface morphology with a uniform grain size distribution. The ferroelectric domain structures were investigated by a combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively). It is demonstrated by both VPFM and LPFM observations that out-of-plane and in-plane lamellar ferroelectric domains coexist in the bilayered thin film. The PLCT/PZT bilayered film possesses good ferroelectric properties with relatively high spontaneous polarization (2P_s = 82 µC/cm²) and remnant polarization (2P_r = 26.2 µC/cm²).