The influence of adsorption phenomena on the impedance spectroscopy of an electrolytic cell

In this work we investigate the influence of the adsorption of ions on the impedance spectroscopy of an electrolytic cell. We consider that the positive and negative ions present in a dielectric liquid are adsorbed in the electrode surfaces with different adsorption energies. This difference in adsorption energies causes an additional plateaux in the limit of the low-frequency range of the real part of the impedance Z . In the same frequency range, a second minimum in the imaginary part of Z is predicted. The theory is illustrated with measurements of the impedance of an electrolytic solution in the frequency range from 10^-2Hz to 1KHz. A comparison between the present model and others from the literature to describe the experimental results is also made.     

Piezo-Optical Effect of Excitons in CuCl

We calculated the stress-induced variations in real part and imaginary part of the dielectric functions in copper chloride (CuCl) by Kramers-Kronig analysis from the piezoreflectance measurements of the 1s Z₃ and 1s Z₁₂ excitons in two configurations of the applied stress X // [001] and X // [110]. From the data of the deduced stress-induced variations in real part and imaginary part of the dielectric functions, the three independent complex components W ₁₁ , W ₁₂ , and W ₄₄ of the fourth-rank linear piezo-optical tensor were determined.     

Equivalent parameters of a Josephson junction in a microwave SQUID structure

The equivalent parameters of a Josephson junction in a microwave SQUID structure are calculated on the basis of relations obtained as a result of an analysis of the operation of an rf SQUID. This analysis is based on the sawtooth variation of the voltage on the resonator as a function of the constant flux bias. The quantitative characteristics permit regarding the Josephson junction as a linear impedance in the rf or microwave circuit, whose real and imaginary parts are controlled by the constant magnetic flux passing through the SQUID loop. Zh. Tekh. Fiz. 69, 106–112 (November 1999)     

The transverse acoustic impedance of an inhomogeneous viscous fluid

The transverse acoustic impedance Z of a fluid can be determined from measurements of the complex reflection coefficient of a transverse ultrasonic wave incident on a plane solid/fluid interface. Inhomogeneities in the fluid close to the solid surface may have a significant effect on the measured values of Z. We have derived the Riccati equation which determines Z in an inhomogeneous viscous fluid, using transmission line theory. This equation was integrated numerically to obtain the impedance of viscous films and for inhomogeneities due to healing lengths and van der Waals forces near the solid/fluid interface. The results show that the measurement of both the real and imaginary parts of Z can be a powerful technique for investigating any inhomogeneities which occur on a length scale comparable with the viscous penetration depth in the fluid.     

Peculiarities of the Giant Magnetoimpedance in Permalloy-Based Film Structures in the Important Temperature Range for Practical Applications

Multilayer structures based on Fe19Ni81 films have been obtained by ion-plasma sputtering and investigated on an impedance spectroscopy apparatus equipped with a temperature unit. An increase in the magnetoimpedance ratios for the total impedance and its real part has been found for the multilayer structure (Cu/FeNi)₅/Cu/(Cu/FeNi)₅ upon heating from 25 to 50°C. The maximum of the giant magnetoimpedance ratio of the total impedance ΔZ/Z = 56% has been observed at a frequency of 80 MHz with a sensitivity of 18%/Oe, while the maximum of the real part ΔR/R = 170% was observed at the frequency of 10 MHz with the sensitivity of 46%/Oe. Magnetization and resistivity at the direct current have been found to depend insignificantly on the temperature and, hence, the relaxation mechanism due to the magnetoelastic anisotropy was proposed as the most probable mechanism of increasing the value and sensitivity of the magnetoimpedance effect.     

Study on ionic conductivity and dielectric properties of PEO-based solid nanocomposite polymer electrolytes

The ionic conductivity and dielectric properties of the solid nanocomposite polymer electrolytes formed by dispersing a low particle-sized TiO₂ ceramic filler in a poly (ethylene oxide) (PEO)-AgNO₃ matrix are presented and discussed. The solid nanocomposite polymer electrolytes are prepared by hot press method. The optimum conducting solid polymer electrolyte of polymer PEO and salt AgNO₃ is used as host matrix and TiO₂ as filler. From the filler concentration-dependent conductivity study, the maximum ionic conductivity at room temperature is obtained for 10 wt% of TiO₂. The real part of impedance (Z′) and imaginary part of impedance (Z″) are analyzed using an LCR meter. The dielectric properties of the highest conducting solid polymer electrolyte are analyzed using dielectric permittivity (ε′), dielectric loss (ε″), loss tangent (tan δ), real part of the electric modulus (M′), and imaginary part of the electric modulus (M″). It is observed that the dielectric constant (ε′) increases sharply towards the lower frequencies due to the electrode polarization effect. The maxima of the loss tangent (tan δ) shift towards higher frequencies with increasing temperature. The peaks observed in the imaginary part of the electric modulus (M″) due to conductivity relaxation shows that the material is ionic conductor. The enhancement in ionic conductivity is observed when nanosized TiO₂ is added into the solid polymer electrolyte.     

Bi0.5Ba0.5FeO3 陶瓷的电性能及阻抗分析

以传统的固相反应法制备了Bi_0.5Ba_0.5FeO₃陶瓷,并采用X射线衍射仪、扫描电子显微镜、直流阻温测试仪和交流阻抗分析仪测试了Bi_0.5Ba_0.5FeO₃陶瓷的微结构和电性能.分析结果表明:Bi_0.5Ba_0.5FeO₃陶瓷具有立方钙钛矿结构,颗粒尺寸约1.0 μm;在16—280 ℃范围内,Bi_0.5Ba_0.5FeO₃陶瓷表现出明显的负温度系数热敏效应,其热敏常数、活化能分别为6490 K及0.558 eV;介电温谱揭示,在280 ℃下Bi_0.5Ba_0.5FeO₃陶瓷材料没有出现相变行为.对于交流阻抗谱,采用3个串联的RQ(R与Q为并联)等效部件来拟合分析,拟合结果表明拟合数据与实验数据高度匹配,且这3个等效部件分别代表晶界、晶粒和晶壳的贡献.3个部件中,晶粒对陶瓷电阻阻值的影响最大,晶壳贡献次之,晶界最小,且3个部件电阻值都显示出负温度系数效应.在25—115 ℃范围内,电学模量虚部峰频与阻抗虚部峰频始终不匹配,意味着Bi_0.5Ba_0.5FeO₃陶瓷体内部一直表现出局域导电机理. 关键词： 0.5Ba_0.5FeO₃陶瓷')" href="#">Bi_0.5Ba_0.5FeO₃陶瓷 电性能 阻抗分析     

A FEM-based method to determine the complex material properties of piezoelectric disks

Numerical simulations allow modeling piezoelectric devices and ultrasonic transducers. However, the accuracy in the results is limited by the precise knowledge of the elastic, dielectric and piezoelectric properties of the piezoelectric material. To introduce the energy losses, these properties can be represented by complex numbers, where the real part of the model essentially determines the resonance frequencies and the imaginary part determines the amplitude of each resonant mode. In this work, a method based on the Finite Element Method (FEM) is modified to obtain the imaginary material properties of piezoelectric disks. The material properties are determined from the electrical impedance curve of the disk, which is measured by an impedance analyzer. The method consists in obtaining the material properties that minimize the error between experimental and numerical impedance curves over a wide range of frequencies. The proposed methodology starts with a sensitivity analysis of each parameter, determining the influence of each parameter over a set of resonant modes. Sensitivity results are used to implement a preliminary algorithm approaching the solution in order to avoid the search to be trapped into a local minimum. The method is applied to determine the material properties of a Pz27 disk sample from Ferroperm. The obtained properties are used to calculate the electrical impedance curve of the disk with a Finite Element algorithm, which is compared with the experimental electrical impedance curve. Additionally, the results were validated by comparing the numerical displacement profile with the displacements measured by a laser Doppler vibrometer. The comparison between the numerical and experimental results shows excellent agreement for both electrical impedance curve and for the displacement profile over the disk surface. The agreement between numerical and experimental displacement profiles shows that, although only the electrical impedance curve is considered in the adjustment procedure, the obtained material properties allow simulating the displacement amplitude accurately.     

Line profile of the Q01(1) vibrational resonance in H2 in the zone of dicke narrowing

A new method of high resolution non-linear spectroscopy based on the detection of the anti-Stokes intensity arising from a resonant four-photon coherent interaction is applied to the determination of the line profile of the Raman resonance Q₀₁(1) in hydrogen gas. The real part as well as the imaginary part of the non-linear Raman susceptibility has been observed in a thermodynamical condition for the gas in which the Dicke narrowing process and the dephasing collision-broadening effect determine competitively the shape of the resonance line.     

Structural and ac electrical properties of a newly synthesized single phase rare earth double perovskite oxide: Ba2CeNbO6

A single phase rare earth double perovskite oxide Ba₂CeNbO₆ (BCN) is synthesized by solid-state reaction technique for the first time. The X-ray diffraction pattern of the sample at room temperature shows monoclinic structure, with the lattice parameters, a=5.9763 Å, b=5.975 Å and c=8.48 Å and β=90.04°. Impedance spectroscopy is used to study the ac electrical behavior of this material as a function of frequency (10²-10⁶ Hz) at various temperatures (30-450 °C). A relaxation is observed in the entire temperature range. Conduction mechanism is investigated by fitting the complex impedance data to Cole-Cole equation. Complex impedance plane plots show only one semicircular arc, indicating only the grain contribution of dielectric relaxation. The scaling behavior of imaginary part of electric modulus (M″) and imaginary part of electrical impedance (Z″) suggests that the relaxation describes the same mechanism at various temperatures. The frequency dependence of conductivity is interpreted in terms of the jump relaxation model and is fitted to Jonscher's power law. The values of dc conductivities extracted from the Jonscher power law varies from 2.79×10⁻⁷ to 3.5×10⁻⁵ Sm⁻¹ with the increase in temperature from 100 to 450 °C. The activation energies (0.37 eV) extracted from M″(ω) and Z″(ω) peaks are found to follow the Arrhenius law.     

Synthesis and electrical properties of Y2O3: Dy3+ & Eu3+ nanoparticles

Yttrium oxide (Y₂O₃) doped with Dy³⁺ & Eu³⁺ nanoparticle has been synthesized by solution combustion method. The formation of the compounds has been checked by X-ray diffraction method. The crystallite/particle size has been measured using Scherrer formula as well as by transmission electron microscopy which show that the size of the particles are in the nanorange. The frequency and temperature dependent variation of impedance Z*, dielectric constant (ε′), dielectric loss (ε″) and AC conductivity (σ) of Y₂O₃: Dy³⁺ & Eu³⁺ nanoparticles were also measured. The real and imaginary part of complex impedance makes semicircle in the complex plane. The center of semicircle arc is found to be shifted toward higher value of real part of impedance with increasing temperature. This indicates that the conductivity of the material increases with the increase in temperature. Cole–Cole plots demonstrate that the dielectric relaxation process occurs in the material. The AC conductivity (σ _AC) increases with the increase in temperature within the frequency range of 10³–10⁷ Hz confirming the hopping of the electrons in the conduction process. The value of impedance decreases sharply with increasing frequency and attains minimum value after 10⁵ Hz at all temperatures.     

场分析法与阻抗叠加方法在速调管输出腔间隙阻抗计算中的应用

 从分析速调管输出回路的电磁场分量入手，结合微波电路理论，提出了计算速调管输出回路间隙阻抗的场分析法。对于在谐振模式交叠频带上，群聚电子束电流同时与各模式的阻抗相作用，总阻抗是各模式阻抗的代数叠加的情况，提出了阻抗叠加方法。该方法原则上可求解任意给定间隙电阻所对应的间隙电抗值。计算表明，场分析法与等效间隙阻抗法计算结果最大相对误差为1.5％，阻抗叠加方法计算结果与冷测数据最大相对误差为10％。分析表明，多个谐振模式的引进是速调管输出腔加载滤波器展宽频带的物理实质。     

Restoring good high energy behaviour in Higgs production via W fusion at the LHC

The W-fusion scattering process for off-shell W bosons is studied, focusing on the issue of its high-energy behaviour which is known to be anomalous. It is shown that the unitarity violating terms can be isolated and extracted in a well-defined and efficient way using the pinch- technique. This restores the good high energy behaviour of the cross section and, in particular, makes possible the identification of the Higgs resonance in the invariant mass distribution of the Z pair. The discarded terms, which are proportional to the off-shellness of the W bosons, cancel against similar terms originating from the remaining diagrams for the full physical process . This cancellation ensures the gauge invariance of our result, which therefore constitutes a meaningful separation between signal andbackground when they both contribute coherently. Equipped with this result, we are able to define a resonant approximation for the process which circumvents the problem of good high energy behaviour without having to resort to the lengthy calculation of the complete set of diagrams. In this approximation only the W- and Z-fusion signal graphs are included, i.e. the ones which contain the Higgs resonance. We have verified that the approximate resonant cross section describes very well the full result not only close to the resonance but also beyond it. Received: 30 January 1999 / Published online: 20 May 1999     

Resonantly enhanced real hyperpolarizability

We show theoretically and experimentally how the first hyperpolarizability of a three-level molecule at a two-photon resonance can obtain a real value with strong resonant enhancement. This phenomenon arises from destructive interference of the usually dominant imaginary parts of the resonant hyperpolarizability.     

NMR Mössbauer double resonance in tantalum

Absorption spectra of Mössbauer ¹⁸¹Ta¹(W) radiation in tantalum have been measured with the source placed in a static magnetic field H_O ≈ 3400 Oe with a rf magnetic field resonant with respect to the frequency of the excited state 3 MHz with amplitude of 300 and 360 Oe, a rf field of 4 MHz with an amplitude of 300 Oe and without rf field. The dramatic change of the spectrum in the resonant field of 300 and 360 Oe, consistent with the theoretical prediction, is evidence for the observation of the NMR Mössbauer double resonance.     

Electrical conductivity of BaTi4O9 film prepared by laser chemical vapor deposition method

A BaTi₄O₉ film was prepared on a Pt/Ti/SiO₂/Si substrate by a laser chemical vapor deposition method and was investigated by impedance spectroscopy over ranges of temperature (300–1073 K) and frequency (10²–10⁷ Hz). Plots between real and imaginary parts of the impedance (Z′ and Z′′) suggest the presence of two relaxation regimes, which were attributed to grain and grain boundary responses. The conduction of both grains and grain boundaries obeys the Arrhenius format with activation energies of respectively 1.45 and 1.24 eV. The close activation energies indicate that the conduction in BaTi₄O₉ film is mainly by oxygen vacancies.     

Optical detection of Yb+ trapped in an rf trap

The fluorescence from Yb⁺ ions trapped in an rf trap was detected by driving the²S_1/2−²P_1/2 transition at 369.52 nm with the radiation generated by sum-frequency mixing of diode-laser and argon-ion-laser radiation. The rf resonance absorption signal as well as the fluorescence signal, when the Yb⁺ ions were continuously irradiated by the resonant uv radiation, faded out with a decay time shorter than the storage time. This observation suggests that the Yb⁺ ions disappeared from the trap with the irradiation of the resonant uv radiation.     

Bi0.5Ba0.5Fe0.5Ti0.49Nb0.01O3热敏陶瓷的微结构和电学性能研究

采用固相合成工艺,制备了Bi_05Ba_05Fe_05Ti_049Nb_001O₃（BBFTN）热敏陶瓷,借助X射线衍射仪、扫描电子显微镜、阻温测试仪和交流阻抗谱考察其微结构、直流电阻、介电特性、阻抗和电学模量方面的电学性能. 结果表明：BBFTN材料依然为立方钙钛矿结构,平均晶粒尺寸约为10 μm,晶格常数相对于BaTiO₃的晶格常数有所变大;室温电 关键词： 05Ba_05Fe_05Ti_049Nb_001O₃')" href="#">Bi_05Ba_05Fe_05Ti_049Nb_001O₃ 微结构 电学性能     

Contribution of the tensor component to the light shift of the rf optical microwave resonance frequency in rubidium vapor

We have calculated the tensor component of the light shift for the frequency of the rf optical microwave resonance on the magnetically independen 0−0 and 1, −1 transitions in rubidium-87 atoms under conditions of isotope filtering of the resonant pump light. We have observed a difference between the temperatures of the filter cell at which a zero frequency shift is achieved for the rf optical resonance for these transitions. We have noted that selective optical pumping on theD ₁ lines is advisable when using a two-photon microwave transition in rubidium vapor in applications. St. Petersburg State Technical University, St. Petersburg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 2, pp. 86–90, February, 1999.     

Al和N共掺对Zn_(1-x)Mg_xO光学性质的影响

基于密度泛函理论第一性原理方法计算了Al和N共掺对Zn1-xMgxO在紫外光波段和可见光波段光学性质的影响.计算结果表明:光学性质变化主要发生在低能区,在高能区光学性质基本保持不变.介电函数虚部、吸收光谱和消光系数计算表明,Al和N共掺后Zn1-xMgxO的光学吸收边产生红移,对部分紫外光和可见光的吸收增强.介电函数实部和反射光谱计算表明,Al和N共掺后Zn1-xMgxO的反射峰强度增大,静态介电常数ε1(0)从2.64增大为3.23.能量损失谱的计算表明,Al和N共掺后Zn1-xMgxO的等离子体共振频率发生蓝移,共振频率的振幅增大.