Dependences on the Composition and a Comparison of Electrolytic Properties of Some Germanium-Containing Quasi-binary Salt Systems

Germanium-containing quasi-binary salt systems GeSe-GeI₂ and NaI-GeI₂ (GeI₂ is a dopant) are studied by methods of electroconductance and x-ray diffraction analysis (XRDA). The conductivity isotherms combined with the XRDA data show that the domain of restricted solid solutions in these systems comes to 3 and 1 mol % GeI₂, respectively. The maximal electrolytic admittance is observed at 2 and 0.25 mol % GeI₂ in GeSe-GeI₂ and NaI-GeI₂ systems. The GeSe system has better ceramic properties, is less susceptible to water traces, and has higher conductivity and lower activation energy for conduction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 616–619.Original Russian Text Copyright © 2005 by Leushina, Danilov, Zlomanov.     

Ionic conductivity of superionic conducting glasses in the pseudobinary system AgIAg2MoO4

The ionic conductivity was measured in the temperature range 250–300 K as a function of composition of superionic conducting glasses in the pseudobinary system AgIAg₂MoO₄. The conductivity, ranging from 10^?2 to 10^?4 Ω^?1 cm^?1 at room temperature, increases linearly in logarithmic scale with increasing AgI content, while the total silver ion concentration remains nearly constant in the whole glass-forming region of the present system. Such a composition dependence of conductivity is considered to be evidence that only a fraction of the silver ions in glass contributes to the ionic conduction. The conductivity and the activation energy for conduction differ slightly between bulk glasses and pressed pellets of pulverized glasses. The close agreement in bulk glasses and pellets suggests that bulk rather than grain boundary or surface diffusion dominates the conduction process in the present glasses.     

Use of solid electrolyte GeSe-GeI<Subscript>2</Subscript> for electrochemical doping with germanium

Lead tellurite is study to show that solid electrolyte GeSe-GeI₂, which has the optimum composition and contains 5 mol % of GeI₂, can in principle be used for electrochemical doping of semiconducting materials with germanium by the coulometric titration method. Some parameters of the coulometric titration are considered. The doping efficiency is monitored by determining variations in the concentration of charge carriers using the Hall method and by measuring the EMF of corresponding galvanic cells.     

Ionic conductivity in KCl-doped polycrystalline SrCl2

Conductivity studies on polycrystalline SrCl₂ doped with KCl have been carried out. The results are in substantial agreement with published results for single crystal work on SrCl₂, the activation energies being 1.8 eV for the intrinsic region, 0.35 eV for the extrinsic region, and 0.45 eV for the regions in which association of defects occurs. Most significant was the discovery of metastable electrolytes (4–5 mole% KCl in SrCl₂) having a conductivity of 1 × 10^?6 ohm^?1 cm^?1 at room temperature. These supersaturated solutions could be heat cycled up to 72°C, and they retained their initial conductivity after storage for 6 months at room temperature. This indicates that the equilibrium solubility of a dopant is not necessarily the limiting factor for extrinsic conductance in a solid material.     

Few‐Layer Nanosheets of n‐Type SnSe2

Layered p‐block metal chalcogenides are renowned for thermoelectric energy conversion due to their low thermal conductivity caused by bonding asymmetry and anharmonicity. Recently, single crystalline layered SnSe has created sensation in thermoelectrics due to its ultralow thermal conductivity and high thermoelectric figure of merit. Tin diselenide (SnSe₂), an additional layered compound belonging to the Sn‐Se phase diagram, possesses a CdI₂‐type structure. However, synthesis of pure‐phase bulk SnSe₂ by a conventional solid‐state route is still remains challenging. A simple solution‐based low‐temperature synthesis is presented of ultrathin (3–5 nm) few layers (4–6 layers) nanosheets of Cl‐doped SnSe₂, which possess n‐type carrier concentration of 2×10¹⁸ cm^?3 with carrier mobility of about 30 cm² V^?1 s^?1 at room temperature. SnSe₂ has a band gap of about 1.6 eV and semiconducting electronic transport in the 300–630 K range. An ultralow thermal conductivity of about 0.67 Wm^?1 K^?1 was achieved at room temperature in a hot‐pressed dense pellet of Cl‐doped SnSe₂ nanosheets due to the anisotropic layered structure, which gives rise to effective phonon scattering.     

Microstructure and protonic conductivity of H3PO4‐doped polyethylenimine–siloxane chemically covalently organic–inorganic hybrids

The chemically covalent polyethylenimine–siloxane hybrids doped with various amounts of ortho‐phosphoric acid (H₃PO₄) were prepared and characterized by FTIR, DSC, TGA, and solid‐state NMR spectra. The protonic conduction behavior of these materials was also investigated by means of impedance measurements. These observations indicate that the hydrogen bonding and protonic interactions exist between the dopant H₃PO₄ and the hybrid host, resulting in an increase in T _g of polyethylenimine segments. These hybrids are thermally stable up to 200 °C from TGA analysis. Conductivity studies show an Arrhenius behavior characteristic and the Grotthus‐like proton conduction, and a high conductivity of 10^?2–10^?3 S cm^?1 at 110 °C in dry atmosphere for the hybrid membrane with H₃PO₄/EI of 0.5. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2135–2144, 2006     

Eosin photodegradation over TiO2 modified by γ-ray irradiation

TiO₂ thin films are elaborated by sol gel on glass substrates and irradiated with ⁶⁰Co γ-rays. The X-ray diffraction, UV-Visible spectroscopy and transport properties are investigated. The films are nominally non stochiometric and the conductivity occurs by thermally activated hopping of lattice polaron. The oxygen vacancies induced by γ-ray irradiation at lower dose (<10 kGy) generate mixed valences Ti⁴⁺/³⁺, thus altering the transport properties. The photo-electrochemical characterisation is undertaken to evaluate the photo catalytic performance. The Mott-Schottky plots are characteristic of n type conduction from which a flat band potential of ?0.62 V _SCE and a donor density of 5 × 10¹⁷ cm^?3 are determined for the most active film. The Nyquist plot exhibits a semi-circular arc whose center lies below the real axis, due to the constant phase element (CPE). The energy band diagram shows the potentiality of the films for the eosin photodegradation. 68% of initial concentration (10 mg L^?1) disappears after 2 h of exposure to the solar light. TiO₂ irradiated with gamma dose of 10 kGy shows the best efficiency, due to the resistance decrees and high electron mobility (25 cm² V^?1 s^?1). The eosin oxidation follows a first order kinetic with a rate constant of 6 × 10^?2 min^?1.     

Ba1.03Ce0.8 Ho0.2O3-α固体电解质的制备和电性能

采用高温固相反应法制备了非化学计量组成的Ba1.03Ce0.8 Ho0.2O3-α 固体电解质,用XRD和SEM对其相组成和表面及断面形貌进行了表征。用气体浓差电池方法测定了材料在600～1000 ℃温度范围内,干燥空气、湿润空气和湿润氢气气氛中的离子迁移数;用交流阻抗谱技术测定了它们在各实验气氛中的电导率。研究了材料的离子导电特性,并与BaCe0.8Ho0.2O3-α 和Ba0.97Ce0.8Ho0.2O3-α 的性能进行了比较。结果表明：该材料为单相钙钛矿型斜方晶结构。在600～1000 ℃温度范围内、干燥空气中,是氧离子与电子空穴的混合导体,氧离子迁移数为0.10～0.36;在湿润空气中,是质子、氧离子与电子空穴的混合导体,质子迁移数为0.11～0.01,氧离子迁移数为0.34～0.30;在湿润氢气气氛中,是纯质子导体,质子迁移数为1。在600～1000 ℃温度范围内,干燥空气、湿润空气和湿润氢气气氛中,非化学计量组成材料(x = 1.03,0.97)的电导率高于化学计量组成材料(x = 1)的电导率,其中,Ba1.03Ce0.8 Ho0.2O3-α的电导率最高 (1000 ℃时、在干燥空气气氛中：3.92×10-2 S·cm-1;在湿润空气气氛中：3.46×10-2 S·cm-1;在湿润氢气气氛中：2.10×10-2 S·cm-1)。Ba1.03Ce0.8 Ho0.2O3-α材料的离子导电性优于BaCe0.8Ho0.2O3-α 和Ba0.97Ce0.8Ho0.2O3-α。     

Electric properties of oxyfluorides Ba2In2O5−0.5x F x with brownmillerite structure

Synthesis of fluoro-substituted substances based on brownmillerite Ba₂In₂O₅ is carried out. The width of the homogeneity region of the Ba₂In₂O_5?0.5x F _x (0 < x ≤ 0.25) solid solution was established using X-ray analysis. Measurement of temperature dependences of conductivity in atmospheres with different partial pressure of water vapor (pH₂O = 3.3 and 2 × 10³ Pa) showed an increase in conductivity at T ≤ 550°C in a humid atmosphere, which is due to appearance of proton transport. The dependence of conductivity on partial oxygen pressure (pO₂ = 0.21 × 10⁵ to 10^?15 Pa) is studied in the temperature range of 500–1000°C; ion transport numbers are calculated. The method of polarization measurements was used to determine transport numbers of fluoride. Total conductivity is divided into ion (proton, oxygen, and fluoride ion) and electron components. Analysis of concentration dependences of conductivities showed that low concentrations of fluoride allow increasing both the total and partial conductivities (oxygen-ion and proton) and, besides, allow shifting the “order-disorder” phase transition by 100°C to the low temperature range.     

Rubidium-cationic conductivity of Rb2−2x Ga2−x A x O4 (A = P, V, Nb, Ta) solid electrolytes

Solid solutions based on rubidium monogallate RbGaO₂ with a general formula Rb_2?2x Ga_2?x A _x O₄ (A = P, V, Nb, and Ta) are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The highest rubidium-cationic conductivity is (1.8–3.9) × 10^?3 S cm^?1 at 400°C and (1.4–2.1) × 10^?2 S cm^?1 at 700°C. These results are compared with the data for rubidium monogallate doped with four-charged cations and solid solutions based on RbAlO₂.     

Superionic Conduction over a Wide Temperature Range in a Metal–Organic Framework Impregnated with Ionic Liquids

Most molecules in confined spaces show markedly different behaviors from those in the bulk. Large pores are composed of two regions: an interface region in which liquids interact with the pore surface, and a core region in which liquids behave as bulk. The realization of a highly mobile ionic liquid (IL) in a mesoporous metal–organic framework (MOF) is now reported. The hybrid shows a high room‐temperature conductivity (4.4×10^?3 S cm^?1) and low activation energy (0.20 eV); both not only are among the best values reported for IL‐incorporated MOFs but also are classified as a superionic conductor. The conductivity reaches over 10^?2 S cm^?1 above 343 K and follows the Vogel–Fulcher–Tammann equation up to ca. 400 K. In particular, the hybrid is advantageous at low temperatures (<263 K), where the ionic conduction is superior to that of bulk IL, making it useful as solid‐state electrolytes for electrochemical devices operating over a wide temperature range.     

Enhanced zinc ion transport in gel polymer electrolyte: effect of nano-sized ZnO dispersion

The effect of the dispersion of zinc oxide (ZnO) nanoparticles in the zinc ion conducting gel polymer electrolyte is studied. Changes in the morphology/structure of the gel polymer electrolyte with the introduction of ZnO particles are distinctly observed using X-ray diffraction and scanning electron microscopy. The nanocomposites offer ionic conductivity values of >10^?3 S cm^?1 with good thermal and electrochemical stabilities. The variation of ionic conductivity with temperature follows the Vogel–Tamman–Fulcher behavior. AC impedance spectroscopy, cyclic voltammetry, and transport number measurements have confirmed Zn²⁺ ion conduction in the gel nanocomposites. An electrochemical stability window from ?2.25 to 2.25 V was obtained from voltammetric studies of nanocomposite films. The cationic (i.e., Zn²⁺ ion) transport number (t ₊) has been found to be significantly enhanced up to a maximum of 0.55 for the dispersion of 10 wt.% ZnO nanoparticles, indicating substantial enhancement in Zn²⁺ ion conductivity. The gel polymer electrolyte nanocomposite films with enhanced Zn²⁺ ion conductivity are useful as separators and electrolytes in Zn rechargeable batteries and other electrochemical applications.     

Lithium-cationic conductivity in the Li4 − 2x Cd x GeO4 system

The lithium-conducting solid electrolytes in the Li_{4 ? 2x} Cd _x GeO₄ (0 ≤ x ≤ 0.6) system are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The specimens with the highest conductivity have a γ-Li₃PO₄-derivative structure. The solid solutions with x = 0.15–0.25 are stable at the room temperature, whereas the specimens with x ≥ 0.3 decompose yielding Li₂CdGeO₄ below 310 ± 10°C. Li_3.6Cd_0.2GeO₄ solid solution exhibits the highest conductivity (5.25 × 10^?2 S cm^?1 at 300°C). The factors, which affect the conductivity of synthesized solid electrolytes, are considered.     

Conductivity and thermal expansion of the Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>1.9</Subscript> solid electrolyte in the oxidizing and reducing atmospheres

Highly compact (99%) solid electrolyte Ce_0.8Gd_0.2O_1.9 with submicron (0.3 μm) grains is synthesized. The dilatometric (20–850°C) and conductivity (180–350°C) measurements are performed on the electrolyte in air and as a function of the partial oxygen pressure \(p_{O_2 } \) (0.21?1×10^?25 atm) at 600, 700, and 800°C. An inflection is found in the temperature dependences of the thermal coefficient of linear expansion and conductivity (impedance measurements) at ～230°C, which is the evidence for a phase transition. The activation energies for conduction in the grain bulk and boundaries differ only slightly, indicating that the grain boundaries’ resistance is caused not by the precipitation of the second phase at the boundaries, but most probably by the presence of intergranular nanopores. The dilatometric measurements confirm a significant increase in the linear dimensions of Ce_0.8Gd_0.2O_1.9 in the reducing atmospheres with a parallel increase in its electron conductivity. The electron conductivity and specific elongation increase proportionally to \(p_{O_2 }^{ - 1/4} \) at all temperatures. The \(p_{O_2 } \) values, at which the transport numbers of ions t _i = 0.5, are determined. They are 10^?22.5, 10^?20, and 10^?18 atm at 600, 700, and 800°C, respectively.     

A Self‐Binding,Melt‐Castable,Crystalline Organic Electrolyte for Sodium Ion Conduction

The preparation and characterization of the cocrystalline solid–organic sodium ion electrolyte NaClO₄(DMF)₃ (DMF=dimethylformamide) is described. The crystal structure of NaClO₄(DMF)₃ reveals parallel channels of Na⁺ and ClO₄^? ions. Pressed pellets of microcrystalline NaClO₄(DMF)₃ exhibit a conductivity of 3×10^?4 S cm^?1 at room temperature with a low activation barrier to conduction of 25 kJ mol^?1. SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55–65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO₄(DMF)₃, permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles.     

Studies on Synthesis and Effect of Dopants on Conductivity and Morphology of Organically Soluble Poly(o-anisidine)

Synthesis of poly(o-anisidine) doped with various protonic acids by using ammonium persulphate as oxidizing agent were carried out in aqueous acid media. Influences of protonic acids on the physicochemical properties were investigated. The various process parameters were optimized to obtain poly(o-anisidine) in the conducting salt phase form. The results are discussed with references to different protonic acids. It was observed that poly(o-anisidine) is highly soluble in organic solvents, such as m-cresol and N-methyl pyrrolidinone (NMP). The polymers were characterized by UV-Visible, FTIR, SEM, XRD and conductivity measurements. A result shows that, different types of dopant acids HCl, H₂SO₄ and HClO₄ affect the morphology and electrical conductivity of the polymer. The electrical conductivity of the polymer follows the order HCl >H₂SO₄>HClO₄. Thus the effect of dopant ion type and the size of its negative ions influence the physico-chemical properties. UV-Vis absorption spectra shows peaks at 740–783 nm with shoulder at 380–420 nm as characteristic peaks for the emeraldine salt (ES) phase of poly(o-anisidine) POA. The FTIR spectra show a broad and intense band at ～2800–3001 cm^?1 and ～1159–1170 cm^?1 that account for the formation of ES phase of the polymer. The X-ray diffraction spectra show a characteristic peak at 20–30^o, 2θ range which reveals partial crystalline structure. The conductivity of the poly(o-anisidne) salt was found to be in the range of 10^?3 to 10^?2 S/cm. SEM studies of poly(o-anisidine) doped with HCl shows the continuous granular uniform morphology with sub-micrometer evenly distributed particles of size ～100–200 nm.     

High-temperature defect structure and electrical conduction in Ni1−xMgxO

The ionic transference number, the electrical conductivity, and Seebeck coefficient of Ni_1?xMg_xO (0.1 ≤ x ≤ 0.9) were measured as functions of temperature (900–1400°C) and oxygen partial pressure (10²–10⁵ Pa). The contribution of ionic conduction to the total conductivity of Ni_0.9Mg_0.1O was of the order of 10^?3?10^?2 at 900–1300°C, which led us to assume that the electronic conduction was predominating in Ni_1?xMg_xO (x ≤ 0.9). The electrical conductivities of both undoped and Al-doped Ni_1?xMg_xO depended on the $\text{1}\text{4}$ power of P_O2, which indicated a significant impurity effect on the defect equilibria and was interpreted as showing that doubly ionized cation vacancies were the dominant point defects at high temperatures. Analyses of the difference in the temperature dependences of conductivity and Seebeck coefficient showed that band-like conduction took place in the NiO-rich composition range (x ≤ 0.1), while thermally activated hopping of small polarons occurred in Ni_1?xMg_xO with x ≥ 0.3. The calculated drift mobility abruptly decreased in the composition region where the conduction mechanism changed.     

Electrical conductivity of titanium pyrophosphate between 100 and 400 °C: effect of sintering temperature and phosphorus content

The synthesis of titanium pyrophosphate is carried out, and the material is sintered at different temperatures between 370 and 970 °C. Yttrium is added during the synthesis to act as acceptor dopant, but it is mainly present in the material in secondary phases. The conductivity is studied systematically as a function of sintering temperature, pH₂O, pO₂, and temperature (100–400 °C). Loss of phosphorus upon sintering above 580–600 °C is confirmed by energy dispersive spectroscopy and combined thermogravimetry and mass spectrometry. The conductivity decreases with increasing sintering temperature and decreasing phosphorus content. The highest conductivity is 5.3?×?10^?4 S cm^?1 at 140 °C in wet air (pH₂O?=?0.22 atm) after sintering at 370 °C. The conductivity is higher in wet atmospheres than in dry atmospheres. The proton conduction mechanism is discussed, and the conductivity is attributed to an amorphous secondary phase at the grain boundaries, associated with the presence of excess phosphorus in the samples. A contribution to the conductivity by point defects in the bulk may explain the conductivity trend in dry air and the difference in conductivity between oxidizing and reducing atmospheres at 300–390 °C. Slow loss of phosphorus by evaporation over time and changes in the distribution of the amorphous phase during testing are suggested as causes of conductivity degradation above 220 °C.     

Combined Intrinsic and Extrinsic Proton Conduction in Robust Covalent Organic Frameworks for Hydrogen Fuel Cell Applications

Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H₃PO₄, the COFs (H₃PO₄@COFs) realize an ultrahigh proton conductivity of 1.13×10^?1 S cm^?1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H₃PO₄@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm^?2 and a maximum current density of 456 mA cm^?2, which exceeds all previously reported COF materials.     

BaCe0.8Ho0.2O3-a陶瓷的性质与应用

Ceramic BaCe0.8Ho0.2O3-α with orthorhombic perovskite structure was prepared by conventional solid state reaction, and its conductivity and ionic transport number were measured by ac impedance spectroscopy and gas concentration cell methods in the temperature range of 600-1000 ℃ in wet hydrogen and wet air, respectively. Using the ceramics as solid electrolyte and porous platinum as electrodes, the hydrogen-air fuel cell was constructed, and the cell performance at temperature from 600-1000 ℃ was examined. The results indicate that the specimen was a pure protonic conductor with the protonic transport number of 1 at temperature from 600-900 ℃ in wet hydrogen, a mixed conductor of proton and electron with the protonic transport number of 0.99 at 1000 ℃. The electronic conduction could be neglected in this case, thus the total conductivity in wet hydrogen was approximately regarded as protonic conductivity. In wet air, the specimen was a mixed conductor of proton, oxide ion and electron hole. The protonic transport numbers were 0.01-0.09, and the oxide-ionic transport numbers were 0.27-0.32. The oxide ionic conductivity was increased with the increase of temperature, but the protonic conductivity displayed a maximum at 900 ℃, due to the combined increase in mobility and depletion of the carriers. The fuel cell could work stably. At 1000 ℃, the maximum short-circuit current density and power output density were 346 mA/cm^2 and 80 mW/cm^2, respectively.