Solid vitreous electrolytes based on the system Li2O-Li2SO4-B2O3-MoO3 for rechargeable lithium power sources

In the given work with the purpose of improvement of moistening ability of sulfoborate solid vitreous electrolyte (SVE) in their structure entered molybdenum oxide (VI). Reduction of wetting angle, i.e. improvement of electrode wetting by a SVE-melt, accompanied by better electrode (aluminium) /SVE interface contact formation. Accordingly, the interface impedance is reduced. As a result of the carried out experiments is established, that the modifying SVE by molybdenum oxide (VI) renders complex positive influence on its physical-chemical properties, namely: improves X-ray-amorphism, raises ionic conductivity, reduces electronic conductivity and effective energy of ion conductivity activation. At comparison of properties modified SVE and "LiPON", it is visible, that the ratio between ionic and electronic conductivity for modified SVE approximately on the order is higher, than for "LiPON". Ionic conductivity of the modified SVE higher than conductivity of "LiPON". The low value of electronic conductivity investigated SVE on a background ionic is the positive factor from the point of view of their use in lithium power sources. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Thermally activated ionic conduction and local structure in solid LiPON thin films

Compact lithium phosphorous oxynitride (LiPON) thin films, as a solid-state electrolyte for all solid-state Li batteries and electrochromic (EC) devices, with the high ratio of the triply coordinated –N< (N_t) over the doubly coordinated –N= (N_d) structural units was deposited by a conventional reactive RF magnetron sputtering of a Li₃PO₄ target at a low pure N₂ pressure. The effect of heat treatment from 200 to 500 °C on the ionic conductivity and local structure of LiPON thin films were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) core level analysis. A dramatical improvement of ionic conductivity from 1.1 to 3.28 μS/cm and microstructure changes were happened on the LiPON thin films while annealed for 1 h at 300 °C, which was linked to structural differences with a highest ratio of –N< over –N= structural units. The work proves that a proper heat treatment on LiPON thin film can effectively improve its ionic conductivity and change its microstructure.     

Influence of sputtering conditions on ionic conductivity of LiPON thin films

LiPON films were deposited using radio-frequency magnetron sputtering in a pure N₂ gas atmosphere. The influence of rf power, N₂ pressure, target–substrate distance and target density on thin film composition and ionic conductivity has been studied. Impedance measurements performed between 25 and 80 °C have indicated that ionic conductivity increases with nitrogen incorporation into the glass structure. An increase in the deposition rate with the target density has also been observed.     

Effects of lithium phosphorous oxynitride film coating on electrochemical performance and thermal stability of graphite anodes

In this study, we investigated the effects of lithium phosphorus oxynitride (LiPON) solid electrolyte thin-film deposition on the electrochemical performance and thermal stability of pristine graphite and carbon-coated graphite composite anodes. The LiPON film was deposited by radio frequency (rf) magnetron sputtering. We studied the thermal stability of the lithiated electrodes when immersed in the presence of a liquid electrolyte by differential scanning calorimetry (DSC).The LiPON thin-film coating suppressed the impedance growth during the cycling process and inhibited the reaction between the lithiated electrode and the electrolyte, thus improving the cycle performance and thermal stability of the graphite electrode. However, for the carbon-coated graphite electrode, the heat evolution below 250 °C decreased, whereas that below 300 °C increased. We attributed this phenomenon to the low thermal stability of the LiPON thin-film coating owing to an exothermic reaction between the LiPON film and the electrolyte that occurs at approximately 290 °C.     

Roughness effects on the double-layer charge capacitance: the case of Helmholtz layer induced roughness attenuation

For electrical double layers, the presence of a Helmholtz layer could lead to electrode roughness attenuation. The latter is assumed of self-affine type which is characterized by the roughness amplitude w, the correlation length ξ, and the roughness exponent H. For sufficiently rough metal electrode surfaces (H1 and/or ratios w/ξ0.1) the diffuse/Helmholtz layer interface would not have the same roughness parameters with the metal electrode surface. If the latter is smoothened at lateral length scales smaller than a healing length Λ (ξ), the diffuse charge capacitance decreases and approaches values close to that of the Gouy–Chapman theory for flat electrodes.     

A study of the metal-ionic conductor interface capacitances. I. Experimental method

In the study of interface capacitances of metal-ionic conductor contacts, difficulties are often encountered to make a reference electrode. The samples used in this work have two blocking electrodes and a third one, located in the bulk of the ionic material. This arrangement is elaborated by successive depositions of gold, lead fluoride, and gold thin films. Each interface capacitance can be obtained from a frequency analysis of the three-probe system. The results show that the structure is not symmetrical, because of differences in the roughness of the electrodes.     

Ta和TaN底电极对原子层淀积HfO2介质MIM电性能的影响

以Ta,TaN为衬底,采用原子层淀积方法制备高介电常数HfO₂介质,比较研究了不同衬底电极对金属-绝缘体-金属（MIM）电容的性能影响.结果表明,采用TaN底电极能够获得较高的电容密度和较小的电容电压系数（VCC）,在1MHz下的其电容密度为7.47fF/μm²,VCC为356ppm/V²和493ppm/V,这归因于TaN底电极与HfO₂介质之间良好的界面特性.两种电容在3?V时漏电流为5×10^-8关键词： 高介电常数 MIM电容 2薄膜')" href="#">HfO₂薄膜 电极     

沉积工艺对二氧化锆薄膜生长特性影响的研究

利用反应离子束溅射、反应磁控溅射和电子束蒸发在K9基底上沉积ZrO2薄膜，并用原子力显微镜对薄膜表面形貌进行测量。通过数值相关运算，对不同工艺条件下薄膜生长界面进行定量描述，得到了薄膜表面的粗糙度指数、横向相关长度、标准偏差粗糙度等参量。由于沉积条件的不同，薄膜生长具有不同的动力学过程。在反应离子束溅射和反应磁控溅射沉积薄膜过程中，薄膜生长动力学行为均可用Kuramoto-Sivashinsky方程来描述，电子束蒸发制备薄膜的过程可以用Mullins扩散模型来描述，并发现在沉积薄膜过程中基底温度和沉积过程的稳定性对薄膜表面特征影响很大。     

Effect of Pb2Ru2O7-x (PRO) conductive interfacial layers on ferroelectric properties of Pt/Pb(Zr0.35Ti0.65)O3/Pt capacitors for nonvolatile memory applications

A conductive material, Pb₂Ru₂O_7-x (PRO), containing Pb in a cubic structure was introduced into a Pt/PZT interface in an attempt to improve the ferroelectric properties of PZT films. PRO and PZT films were prepared by rf magnetron sputtering and chemical solution deposition, respectively. The resistivity of PRO thin films in a hybrid-type electrode (PRO/Pt) structure was approximately 35–45 μΩ·cm and the surface roughness remained constant with increasing annealing temperature. The PRO interlayers suppressed the loss of Pb in PZT layers by diffusion to the Pt/PZT interface. The increase in remanent polarization was largely dependent on the PRO interlayers inserted at the bottom-Pt/PZT interface rather than at the top-Pt/PZT interface. In addition, the leakage-current behavior of PZT films in a sandwich structure was improved substantially compared to the case of PRO interlayers only at the bottom-Pt/PZT interface. Thus, the PRO interlayers play an important role in improving the ferroelectric properties of PZT thin films for use in nonvolatile memory device applications. PACS 68.55.-a; 73.40.Rw; 73.61.Ng; 77.55.+f; 81.15.Cd     

磁控溅射Al膜的AFM性能分析及其制备工艺研究

用原子力显微镜(AFM)对直流溅射和射频溅射制备铝膜的表面粗糙度及颗粒大小进行了分析比较.实验结果表明:溅射功率和溅射时间对铝膜表面粗糙度有影响,通过延长溅射时间或提高溅射功率可使膜的平均颗粒直径增大.     

Electrochemical characteristics of alumina dielectric layers

The electrochemical characteristics of alumina dielectric layers were studied using a surface roughness factor and an impedance spectroscopy. From the limiting diffusion current method, the surface area factor of the dielectric anodic layer with low electrical conductivity was estimated to be 1.03. As alumina dielectric films on Al have a variable stoichiometry, the electrochemical behavior of Al₂O₃ layer can be monitored by evaluating an equivalent circuit with Young impedance of dielectric constant with a vertical decay of conductivity.     

LiPON as a protective layer on graphite anode to extend the storage life of Li-ion battery at elevated temperature

A thin-film lithium phosphorous oxynitride (LiPON) layer on the top of a graphite anode is synthesized via radio frequency magnetron sputtering, whereas the thickness of the film is about 0.3 ~ 1.3 μm. The field emission scanning electron microscopy on the samples confirms the even-coated layer on the anode, while the thickness of layer is reconfirmed by weighing the area density of sputtered anode. The storage experiment at elevated temperature of LiNi_0.8Co_0.15Al_0.05O₂/graphite cells with and without a LiPON layer on anode reveals that the LiPON layer on the anode would restrain the capacity loss when compared with bare anode. Moreover, it is found that a thicker LiPON layer on anode would provide better capacity retention during storage aging. Meanwhile, the electrochemical impedance spectroscopy is recorded during aging and its equivalent circuit simulation is proposed. Also, the anode surface morphology with and without a LiPON layer is observed before and after aging. Based on these investigations and analysis, we conclude that the LiPON layer on the top of the anode would act as a protective layer and improve the capacity retention during storage aging at elevated temperature.     

Effect of melt compounding temperature on dielectric relaxation and ionic conduction in PEO–NaClO<Subscript>4</Subscript>–MMT nanocomposite electrolytes

Polymer nanocomposite electrolytes (PNCEs) of poly(ethylene oxide) and sodium perchlorate monohydrate complexes with montmorillonite (MMT) clay up to 20 wt.% MMT concentration of poly(ethylene oxide) (PEO) are synthesized by melt compounding technique at melting temperature of PEO (∼70 °C) and NaClO₄ monohydrate (∼140 °C). Complex dielectric function, electric modulus, alternating current (ac) electrical conductivity, and impedance properties of these PNCEs films are investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. The direct current conductivity of these materials was determined by fitting the frequency-dependent ac conductivity spectra to the Jonscher power law. The PNCEs films synthesized at melting temperature of NaClO₄ monohydrate have conductivity values lower than that of synthesized at PEO melting temperature. The complex impedance plane plots of these PNCEs films have a semicircular arc in upper frequency region corresponding to the bulk material properties and are followed by a spike in the lower frequency range owing to the electrode polarization phenomena. Relaxation times of electrode polarization and ionic conduction relaxation processes are determined from the frequency values corresponding to peaks in loss tangent and electric modulus loss spectra, respectively. A correlation is observed between the ionic conductivity and dielectric relaxation processes in the investigated PNCEs materials of varying MMT clay concentration. The scaled ac conductivity spectra of these PNCEs materials also obey the ac universality law.     

Dipolar interaction and its interplay with interface roughness

We present a comparison of the strength of the classical dipolar interaction, relative to quantum-mechanical coupling mechanisms like RKKY and complete confinement, between two ferromagnetic films separated by a paramagnetic spacer. The classical dipolar coupling, which vanishes if the two interfaces are perfectly continuous and flat, builds up strength as the interface roughness grows for several models of interface topography. These numerical estimates, carried out for a Co/Cu/Co trilayer show that, in the presence of substantial surface roughness, the dipole-dipole interaction strength is comparable, and at times even larger, than those obtained using other well established mechanisms. These results are also in qualitative agreement with experimental measurements in a variety of multilayer systems. Thus, for rough interfaces, the dipolar interaction cannot be ignored.     

Capacitance dispersion in electrochemical impedance spectroscopy measurements of iodide adsorption on Au(1 1 1)

Electrochemical interfaces that display dispersive characteristics do not present the purely capacitive behaviour predicted by the theory of ideally polarised interfaces. For interfaces involving solid electrodes, capacitance dispersion phenomena in the double layer region are usually attributed to the structural characteristics of the electrode surface as well as to the interfacial region. This paper presents a study of the dispersive characteristics, in the double layer potential region, related to the iodide adsorption on an Au(1 1 1) electrode. The study was performed by using electrochemical impedance spectroscopy, and the corresponding spectra fitted with an equivalent circuit containing a constant phase element (CPE). The fitting results are compared with capacitance curves obtained by chronocoulometry, in order to analyse the relationship between the CPE and the interfacial capacitance. It was observed the occurrence of dispersive behaviour in the potential regions associated with phase transition processes in the adsorbed layer and to the potential induced reconstruction phenomena. On the other hand, in the potential regions where such phenomena do not occur, the interface presents almost pure capacitive behaviour. These observations provide evidence of the strong contribution of the solution properties to the capacitance dispersion.     

Synthesis and characterization of DSSC by using Pt nano-counter electrode: photosensor applications

Pt electrode prepared by chemical method has been employed as counter electrode in dye-sensitized solar cell. TiO₂ nanomaterial was deposited on fluorine-doped tin oxide substrate to be used as photoanode. Structure of the TiO₂ and Pt films was investigated by atomic force microscope. The effect of illumination intensity on the photovoltaic parameters such as open circuit voltage, short circuit current density, output power, fill factor and efficiency of these cells was investigated in the range 2.5–130 mW/cm^?2. The cell efficiency is stable above 70 mW/cm². The fill factor is almost constant all over the studied range of illumination intensity. Impedance spectroscopy of the studied device as the summary measurements of the capacitance–voltage, conductance–voltage and series resistance–voltage characteristics were investigated in a wide range of frequencies (5 kHz–1 MHz). At low frequencies, the capacitance has positive values with peak around the origin due to the interfaces. At 200 and 300 kHz, the capacitance is inverted to negative with further increasing of the positive biasing voltage. Above 400 kHz, C–V profile shows complete negative behavior. Also, the impedance–voltage and phase–voltage characteristics were investigated. This cell shows a new promising device for photosensor applications due to high sensitivity in low and high illuminations.     

Finite element modeling of reverberation and transmission loss in shallow water waveguides with rough boundaries

A finite element model for the reverberation and propagation in a shallow water waveguide with a sandy bottom was calculated for five different environments at a center frequency of 250 Hz. The various environments included a rough water/sediment interface, a rough air/water interface, roughness at both interfaces and downward and upward refracting sound speed profiles with roughness at both interfaces. When compared to other models of reverberation such as ray theory, coupled modes, and parabolic equations, finite elements predicted higher levels of reverberation. At early times, this is due to the "fathometer" return, energy that is normally incident on the boundaries at zero range. At later times, the increased reverberation was due to high angle scattering paths between the two interfaces. Differences in reverberation levels among the environments indicated that scattered energy from the air/water interface is transmitted into the bottom at steep angles. This led to a large decrease in reverberation for a rough air/water interface relative to a rough water/sediment interface. Sound speed profile effects on reverberation were minimal at this frequency range. Calculations of the scintillation index of the different environments indicated that most of the reverberation was relatively Rayleigh-like with heavier tailed distributions at longer ranges.     

Experimental limitations in impedance spectroscopy: Part VI. Four-point measurements of solid materials systems

Four-point impedance spectroscopy of solid materials systems is severely hampered by unavoidable voltage-divider effects associated with the reference electrodes. As demonstrated by test circuit studies and experiments with Pt/YSZ/Pt cells (with embedded silver reference electrodes), high impedance reference electrodes can produce distorted and erroneous impedance data. The relationships between these data and the sample properties (conductivity, dielectric constant) and instrument limitations (input impedance/capacitance) are derived. Successful four-point impedance measurements on conductive systems require large effective dielectric constants, which may be unattainable in bulk solids, but are often associated with internal interfaces.     

Stability of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al in ionic liquid BMI.BF<Subscript>4</Subscript>/γ-butyrolactone electrolytes for use in electrolytic capacitors

The stability of aluminium oxide has been investigated in mixtures of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF₄) and γ-butyrolactone (GBL) for application as the impregnation electrolyte of aluminium electrolytic capacitors. Ionic conductivity measurements of BMI.BF₄/GBL electrolytes at different temperatures were performed, as well as electrochemical impedance spectroscopy and cyclic voltammetry experiments. The results show that the highest ionic conductivity value of 40 mS cm^?1 (70 °C) is achieved in electrolyte x _BMI.BF4 = 0.2. The total capacitance values, associated with the dielectric oxides, vary between 1 and 8 μF cm^?2 for all studied electrolytes after 30 days of immersion. The polarization resistance and total capacitance of the electrolyte/Al₂O₃/Al system decrease slightly with immersion time, showing the stability of Al₂O₃/Al in ionic liquid BMI.BF₄/GBL electrolytes.