An impedance spectroscopy study in poly(butylene adipate) ionomers

Poly(butylenes adipate) ionomers (PBAi) were synthesized using dimethyl 5‐sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. We have investigated electrical and dielectric properties of the ionomers to evaluate alternating current (AC) parameters such as impedance, conductance, dielectric constant, admittance, susceptance, dielectric loss, and resistance by an impedance spectroscopy. It is seen that the ionic conductances of the ionomers increase with increasing content of DMSI. The AC conductance for the ionomers was found to vary as ω^s with the index s ≥ 1. A decrease in the relative dielectric constant of the ionomers is observed with the increase in the ionic content. The electrical relaxation in the dielectric spectra of the ionomers was not observed due to the orientation polarization of the dipoles. It is also observed that the tangent loss increases with the increase in the ionic content.     

Kapitza resistence of low acoustic impedance solids (ice and bismuth)

Results of the Kapitza resistance between ice and bismuth and superfluid helium in the 1–2K range are presented. Reasonable agreement with theory is obtauned, consistent with the comparatively good acoustic matching between these solids and liquid helium.     

Electric impedance study of elastic alternating propylene-carbon monoxide copolymer (PCO-200)

The electrical properties of elastic alternating propylene-carbon monoxide copolymer (PCO-200) were investigated using the impedance spectroscopy technique. The results revealed a phase transition at about 70 °C where the material transforms from its insulating phase of conductivity in the order of 6×10⁻⁹ to about 9×10⁻⁵ (Ω m)⁻¹, The second phase is characterized by temperature dependent electrical relaxation phenomena. The plot of the complex electric modulus and the complex impedance yields semicircles in the temperature range 70 up to 110 °C and a decreasing radius with increasing temperature. The activation energy was found to be in the order of 0.8 eV.     

Vibrational and impedance spectroscopic analysis of poly(vinyl alcohol)-based solid polymer electrolytes

Solid polymer electrolytes based on poly(vinyl alcohol) (PVA) doped with NH₄Br have been prepared by the solution-casting method. The complex formation between the polymer and the salt has been confirmed by Fourier transform infrared spectroscopy. The highest conductivity at 303 K has been found to be of the order of 10⁻⁴ Scm⁻¹ for 25 mol% NH₄Br-doped PVA system. The ionic transference number of polymer electrolyte has been estimated by Wagner’s polarization method, and the results reveal that the conducting species are predominantly ions. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Surface impedance models for high impedance surfaces

Different analytical and numerical methods for calculating the surface impedance of a high impedance surface (HIS) structure have been studied and compared. In this article, two new approaches are proposed for calculating the surface impedance for general 2D-spatial periodic HIS structures, which include both the symmetric and asymmetric planar structures. Different comparisons are made, among analytical, numerical and experimental results, to validate our numerical calculation.     

About impedance spectra and dynamics of charge carriers in neat poly(ethylene oxide) structures

Impedance spectra of linear and cross-linked poly(ethylene oxide) (PEO) are analyzed in a wide range of temperature. Dielectric responses differ at low and high temperature due to tendency of PEO to crystallization below melting temperature. Extent of crystallization depends on cross-linking density. The network in PEO with high cross-linking density is rigid and morphology transition shifts to very low temperature. Debye-like relaxation appears at low temperature similar as in ionic liquids. Onset of polarization relaxation shifts to higher temperature with increasing mesh size that is coupling of electric and structural relaxation appears. This is also nicely reflected by scaled conductivity. It demonstrates that the structure in cross-linked systems is a superposition of chemical and physical networks. They relax separately at low temperature and frequency under condition of sufficient rigidity.     

The ac conductivity and complex impedance of CuO-doped (Ba0.5Sr0.5)TiO3 ceramic

The AC conductivity and complex impedance spectroscopy of CuO-doped (Ba_0.5Sr_0.5)TiO₃ ceramic were investigated. X-ray diffraction analysis showed that CuO-doped (Ba_0.5Sr_0.5)TiO₃ has a perovskite structure without any pyrochlore phase. Frequency dependent dielectric permittivity was discussed at a different temperature range. The activation energy was calculated and discussed through the Arrehnius equation from the ac conductivity with different frequency plots. CuO-doped (Ba_0.5Sr_0.5)TiO₃ ceramics have a negative temperature coefficient of resistivity. Dependence of impedance spectroscopy on frequency and temperature showed that the conduction process in the CuO-doped (Ba_0.5Sr_0.5)TiO₃ ceramic follows the thermally activated conduction mechanism.     

AC impedance studies on proton conducting polymer electrolyte complexes (PVA+CH3COONH4)

A proton conducting polymer electrolytes of pure polyvinyl alcohol and polyvinyl alcohol complexed with ammonium acetate having different compositions have been prepared by solution cast technique. FTIR spectrum confirms the complexation process. The conductivity of the pure polyvinyl alcohol is in the order 10⁻¹⁰ S/cm at ambient temperature and its value increases 10⁴ times when complexed with 20% ammonium acetate. The Arrhenius plot for all electrolyte shows two different regions above and below the glass transition temperature. A high dielectric loss value is observed for the case of complexed PVA in comparison to pure PVA. Based on the study of relaxation spectra, it is found that the relaxation time decreases with increase in temperature and dopant concentration. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

换能器的阻抗匹配设计

本文从基本的电学原理，详细推导出变压吕的互耦阻抗及变压器的阻抗变换关系，提出了换能器阻抗匹配较理想的设计方法，在工程设计中较好的实用价值。     

Thermal stability and impedance spectroscopy studies of (Cu, Ni) substituted Bi4V2O11 ceramics

Polycrystalline samples of the oxygen ion conductor Bi₂V_0.9Cu_0.1−xNi_xO_5.35 with various contents of nickel (0 ≤ × ≤ 0.1) were investigated. The X-ray powder diffraction revealed the tetragonal structure of all compositions. DTA curves exhibit effects due to phase transition, one endothermic effect during heating and one exothermic one during cooling. The impedance of the ceramics with Pt electrodes was measured in the frequency range 10⁻¹–10⁷ Hz at constant temperatures between 350 and 920 K. The conductivity was determined by nonlinear least-squares analysis of the impedance spectra. Separation of the total resistance into grain interior and grain boundary components was feasible at temperatures below 580 K. The transition temperatures observed in DTA coincide with those observed in conductivity measurements. A phase transition, involving a reordering process of the oxygen ions is considered to be responsible for this phenomenon. The frequency dependent part of the intragrain conductivity was modeled by a constant phase admittance. The effective hopping rate was estimated by comparing the frequency dependent part and the dc limit of the intragrain conductivity. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997.     

Quasi-optical theory of amplification of surface waves propagating above corrugated structures by a relativistic electron beam (impedance approximation)

The impedance model that describes the amplification of a monochromatic wave by a relativistic electron beam that propagates rectilinearly over a corrugated structure is constructed based on quasi-optical approach. In this model, the electric field component acting on electrons is written taking into account induced rf fields of the space charge of the beam. The dispersion equation used to determine the instability increments in various ranges of parameters has been obtained in the weak signal approximation. The efficiency of the energy exchange at the saturation stage of amplification is determined using a 2D nonlinear model in which the propagation of the wave has been described by a parabolic equation with a radiative boundary condition. The possibility of using the system under investigation to amplify submillimeter radiation has been demonstrated.     

Structural,XPS and impedance analysis of LixCoVO4 (x = 0.8, 1.0, 1.2)

Lithium cobalt vanadate Li_xCoVO₄ (x = 0.8; 1.0; 1.2) has been prepared by a solid state reaction method. The XRD analysis confirms the formation of the sample. A new peak has been observed for Li_1.0CoVO₄ and for Li_1.2CoVO₄ indicating the formation of a new phase. The XPS analysis indicates the reduction in the oxidation of vanadium and oxygen with the addition of Li in Li_xCoVO₄ (x = 0.8, 1.0, 1.2). The impedance analysis gives the conductivity value as 2.46 × 10^− 5, 6.16 × 10^− 5, 9 × 10^− 5 Ω^− 1 cm^− 1 for Li_xCoVO₄ (x = 0.8; 1.0; 1.2), all at 623 K. The similarity in the bulk activation energy (E_a) and the activation enthalpy for migration of ions (E_ω) indicate that the conduction in Li_1.2CoVO₄ has been due to hopping mechanism.     

Dielectric and impedance properties of Bi(Zn2/3V1/3)O3 electronic material

A polycrystalline vanadium doped lead free dielectric material of Bi(Zn_2/3V_1/3)O₃ (BZV) has been prepared using a standard high-temperature solid state reaction technique. Its temperature and frequency dependent capacitive, conductive and resistive characteristics are outlined though experimental investigation. The formation of single phase compound of BZV material with orthorhombic crystal symmetry is identified through X-ray diffraction data analysis, and the homogeneous distribution of grains are realized through scanning electron micrograph. The acquaintance of frequency–temperature dependent electrical parameters with the obtained micrograph provides the experimental evidence of contributions of grain as well as grain boundary in its capacitive and resistive characteristics. The negative temperature coefficient of resistance behaviour of the material is revealed from impedance characteristic, and non-Debye type relaxation has been realized from the Nyquist plot. The charge carriers of this electronic compound have both long & short range order that has been validated from the complex modulus and impedance analysis. The prepared electronic material substantiate some important dielectric features which props up the material as promising component for electronic devices.