Anomalous d.c. conductance in Nd+3-doped ferroelectric lead germanate single crystal

Pure lead germanate (LG), 0·1 wt% Nd⁺³-doped lead germanate (LG.1Nd⁺³), 0·2wt% Nd⁺³-doped lead germanate (LG.2Nd⁺³) were grown by controlled cooling of melt. Variation of d.c. conductivity was studied in the temperature range 293°K–523°K. Conductivity increases with increasing temperature, showing semiconducting behaviour for all the compositions under study. The activation energy in ferroelectric phase is larger than in paraelectric phase for all the compositions. The result suggests polaron hopping to be a significant contributor to conduction mechanism.     

Preparation,sintering and electrical behaviour of cobalt,nickel and zinc germanate

Cobalt, nickel and zinc germanate were prepared by solid state reactions between the relevant oxides in air. Ceramics with monophase structures could be obtained by adopting the optimum temperature and time. The as-fired ceramics exhibited insulating properties; however, by an additional heat treatment under reducing conditions, variable electrical conductivity could be induced in the ceramic bodies. Temperature/resistivity characteristics of these materials showed typical semiconducting behaviour. X-ray studies showed that despite the changes in electrical behaviour, and apparent changes in colour after annealing, the structures remained unaltered. Microstructural studies using scanning electron microscopy also showed that there were no substantial changes due to the reductive annealing processes.     

Electrical conductivity and optical absorption studies on NiPc-substituted borate glass matrix

Electrical conductivity and optical absorption of nickel phthalocyanine (NiPc)-substituted borate glass is reported here for the first time. We have successfully prepared NiPc-substituted lithium borate glass at 850 °C and some preliminary studies on this glass are reported. Activation energy and optical band gap were determined for the glass from the Arrhenius plot of conductivity and optical absorption spectra, respectively.     

Interfacial Interaction of Multifunctional GQDs Reinforcing Polymer Electrolytes For All-Solid-State Li Battery

Solid-state polymer electrolytes are highly anticipated for next generation lithium ion batteries with enhanced safety and energy density. However, a major disadvantage of polymer electrolytes is their low ionic conductivity at room temperature. In order to enhance the ionic conductivity, here, graphene quantum dots (GQDs) are employed to improve the poly (ethylene oxide) (PEO) based electrolyte. Owing to the increased amorphous areas of PEO and mobility of Li⁺, GQDs modified composite polymer electrolytes achieved high ionic conductivity and favorable lithium ion transference numbers. Significantly, the abundant hydroxyl groups and amino groups originated from GQDs can serve as Lewis base sites and interact with lithium ions, thus promoting the dissociation of lithium salts and providing more ion pathways. Moreover, lithium dendrite is suppressed, associated with high transference number, enhanced mechanical properties and steady interface stability. It is further observed that all solid-state lithium batteries assembled with GQDs modified composite polymer electrolytes display excellent rate performance and cycling stability.     

Transparent conducting films

We present here a new technique, called vapour phase spray pyrolysis, for deposition ofto andito films. Undopedto film showed semiconducting nature, a sheet resistance of 1088 Ω/□, a donor ionization energy level of 40 meV, average visible transmittance of 75·4% andn-type conductivity. The indium doped (ito) film 10 wt % showed metallic nature, a sheet resistance of 15 Ω/□, average visible transmittance of 80·4 % andp-type conductivity. Thus theto andito films showed fairly good electro-optical qualities, comparable to those obtained by sophisticated and costly techniques.     

Composition dependence of lithium ionic conductivity in lithium nitride-lithium iodide system

Two minima in the lithium ionic conductivity vs. composition curve in the lithium nitride-lithium iodide system are observed at Li₅NI₂ and Li₇N₂I. It is shown that ionic conductivity minimum at the stoichiometric Li₅NI₂ is caused by the increase in the lithium ion concentration.     

Calcium germanate nanowires by vanadium doping with improved photocatalytic activity

Vanadium-doped calcium germanate nanowires were prepared by a simple hydrothermal method. The samples were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and solid UV–Vis diffuse reflectance spectrum. The photocatalytic activity of the vanadium-doped calcium germanate nanowires was investigated by the degradation of methylene blue (MB) under solar light irradiation. The results show that the vanadium-doped calcium germanate nanowires are composed of rhombohedral Ca₃GeO₅ and orthorhombic CaV₃O₇ phases. The nanowires have the diameter and length of 50–200 nm and several dozens of micrometres, respectively. The band gap of the vanadium-doped calcium germanate nanowires strongly depends on the vanadium doping mass percentage. The absorption spectrum can be broadened to visible light region. The photocatalytic activity of the vanadium-doped calcium germanate nanowires is remarkably improved. Vanadium-doped calcium germanate nanowires with the vanadium doping mass percentage of 10% have the highest photocatalytic activity for MB degradation under solar light irradiation.     

溶胶—凝胶法合成Li2＋xBxSi1—xO3及其离子导电性能的研究

用溶胶－凝胶法合成了Ｌｉ２＋ｘＢｘＳｉ１－ｘＯ３（ｘ＝０－０．５）,发现形成固溶体的范围是０〈ｘ≤０．２。对其离子导电性的研究发现,当ｘ＝０．３时出现电导率极大值。     

Lithium garnets: Synthesis,structure, Li+ conductivity,Li+ dynamics and applications

Inorganic solid fast Li⁺ conductors based batteries are expected to overcome the limitations over safety concerns of flammable organic polymer electrolytes based Li⁺ batteries. Hence, an all-solid-state Li⁺ battery using non-flammable solid electrolyte have attracted much attention as next-generation battery. Therefore, in the development of all-solid-state lithium rechargeable batteries, it is important to search for a solid electrolyte material that has high Li⁺ conductivity, low electronic conductivity, fast charge transfer at the electrode interface and wide electrochemical window stability against potential electrodes and lithium metal. Hence, significant research effort must be directed towards developing novel fast Li⁺ conductors as electrolytes in all-solid-state lithium batteries. Among the reported inorganic solid Li⁺ conductive oxides, garnet-like structural compounds received considerable attention in recent times for potential application as electrolytes in all-solid-state lithium batteries. The focus of this review is to provide comprehensive overview towards the importance of solid fast lithium ion conductors, advantages of lithium garnets over other ceramic lithium ion conductors and understanding different strategies on synthesis of lithium garnets. Attempts have also been made to understand relationship between the structure, Li⁺ conduction and Li⁺ dynamics of lithium garnets. The status of lithium garnets as solid electrolyte in electrochemical devices like all-solid state lithium battery, lithium-air battery and sensor are also discussed.     

Infra-red study of polymerisation in silver,thallium, and thallium aluminogermanate glasses

The infra-red spectra of silver germanate, thallium germanate, and thallium aluminogermanate glasses are presented for the 1100 cm^–1 to 400 cm^–1 region. The pseudo rare gas type Tl⁺ and Ag⁺ ions produce spectral shifts in binary germanate glasses that are similar to those reported for alkali ions. Differences for Tl⁺ may be due to its high atomic weight and polarising power. The infra-red spectral shifts observed for thallium aluminogermanate glasses are those expected if GeO₆ octahedra disappear while AlO₄ tetrahedra engage in network repair. A structurally sensitive technique for displaying ternary oxide glass infra-red spectra is outlined. This technique is capable of discerning different modes of network depolymerisation and polymerisation in ternary germanate and silicate glasses.     

Aliphatic Polycarbonate‐Based Solid‐State Polymer Electrolytes for Advanced Lithium Batteries: Advances and Perspective

Conventional liquid electrolytes based lithium‐ion batteries (LIBs) might suffer from serious safety hazards. Solid‐state polymer electrolytes (SPEs) are very promising candidate with high security for advanced LIBs. However, the quintessential frailties of pristine polyethylene oxide/lithium salts SPEs are poor ionic conductivity (≈10⁻⁸ S cm⁻¹) at 25 °C and narrow electrochemical window (<4 V). Many innovative researches are carried out to enhance their lithium‐ion conductivity (10⁻⁴ S cm⁻¹ at 25 °C), which is still far from meeting the needs of high‐performance power LIBs at ambient temperature. Therefore, it is a pressing urgency of exploring novel polymer host materials for advanced SPEs aimed to develop high‐performance solid lithium batteries. Aliphatic polycarbonate, an emerging and promising solid polymer electrolyte, has attracted much attention of academia and industry. The amorphous structure, flexible chain segments, and high dielectric constant endow this class of polymer electrolyte excellent comprehensive performance especially in ionic conductivity, electrochemical stability, and thermally dimensional stability. To date, many types of aliphatic polycarbonate solid polymer electrolyte are discovered. Herein, the latest developments on aliphatic polycarbonate SPEs for solid‐state lithium batteries are summarized. Finally, main challenges and perspective of aliphatic polycarbonate solid polymer electrolytes are illustrated at the end of this review.     

Intrinsically Optimizing Charge Transfer via Tuning Charge/Discharge Mode for Lithium–Oxygen Batteries

Lithium–oxygen batteries have an ultrahigh theoretical energy density, almost ten times higher than lithium‐ion batteries. The poor conductivity of the discharge product Li₂O₂, however, severely raises the charge overpotential and pulls down the cyclability. Here, a simple and effective strategy is presented for regular formation of lithium vacancies in the discharge product via tuning charge/discharge mode, and their effects on the charge transfer behavior. The effects of the discharge current density on the lithium vacancies, ionic conductivity, and electronic conductivity of the discharge product Li₂O₂ are systematically investigated via electron spin resonance, spin‐alignment echo nuclear magnetic resonance, and tungsten nanomanipulators, respectively. The study by density functional theory indicates that the lithium vacancies in Li₂O₂ generated during the discharge process are highly dependent on the current density. High current can induce a high vacancy density, which enhances the electronic conductivity and reduces the overpotential. Meanwhile, with increasing discharge current, the morphology of the Li₂O₂ changes from microtoroids to thin nanoplatelets, effectively shortening the charge transfer distance and improving the cycling performance. The Li₂O₂ grown in fast discharge mode is more easily decomposed in the following charging process. The lithium–oxygen battery cycling in fast‐discharge/slow‐charge mode exhibits low overpotential and long cycle life.     

锂磷氧氮电解质在无机薄膜锂电池中的应用

锂磷氧氮(LiPON,lithium phosphorous oxynitride)薄膜具有较高的离子电导率,极低的电子电导率,很宽的电化学稳定窗口等优点而成为全固态无机薄膜锂电池首选的电解质材料.简要介绍了LiPON薄膜的特性与制备方法,综述了国内外LiPON薄膜为电解质的薄膜锂电池的研究情况,并简要评述了目前薄膜锂电池制备中遇到的困难和今后的研究方向.     

Preparation and characterization of metalorganic chemical vapor deposited nickel oxide and lithium nickel oxide thin films

Thin films of nickel oxide and lithium nickel oxide were deposited through the pyrolysis of nickel acetylacetonate and lithium nickel acetylacetonate, respectively in the temperature range 350–420 °C. The single solid source precursors, nickel acetylacetonate and lithium nickel acetylacetonate were prepared and characterized using Energy Dispersive X-Ray Fluorescence (EDXRF), X-Ray Diffraction (XRD) and infrared spectroscopy. The composition, optical and electrical properties of the prepared thin films were analysed using a variety of techniques, including, Rutherford Backscattering Spectroscopy (RBS), EDXRF, XRD, UV–Visible Spectrophotometry and van der Pauw conductivity method. The amount of metals in the prepared thin films did not reflect the ratio of the metals in the precursor but was found to depend on the deposition temperature. The energy gaps of the nickel oxide and lithium nickel oxide thin films are 3.7 and 3.2 eV, respectively. The electrical conductivity showed that lithium nickel oxide thin film has an activation energy of 0.11 eV. The conduction was explained by a hopping mechanism.     

Factors affecting the magnitudes and anisotropies of the thermal and electrical conductivities of poly(l-lactic) acid composites with carbon fibers of various sizes

Investigation of the thermal and electrical conductivities of poly(l-lactic acid) composites containing carbon fibers (CFs) of various sizes has revealed that the thermal conductivity depends largely on the length of the CFs in the composites and that the electrical conductivity depends largely on the aspect ratio of the CFs. These different dependencies are due to the effect of the number of interfaces between the CFs in a percolation network formed in the composites, where electron transport is enhanced but phonon thermal conduction is limited by phonon scattering at the interfaces between the CFs. The anisotropy of each conductivity is also influenced by the length of the CFs, which could determine the alignment of the CFs in the molded composites.     

Bulk ac conductivity studies of lithium substituted layered sodium trititanates (Na<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>7</Subscript>)

Lithium mixed sodium trititanates with 0.3, 0.5 and 1.0 M percentage of Li₂CO₃ (general formula Na_2−X Li _X Ti₃O₇) have prepared by a high temperature solid-state reaction route. EPR analysis, high temperature range (473–773 K) and variable frequency range (100 Hz–1 MHz) ac conductivity measurements were carried out on prepared sample. The lithium ions are accommodated with the sodium ions in the interlayer space. The EPR specta of lithium mixed sodium Trititanates confirm the partial reduction of Ti⁴⁺ ions to Ti³⁺. Four distinct regions have identified in the LnσT versus 1,000/T plots. Various conduction mechanisms which dependence on concentration, frequency and temperature are reported in this paper for lithium mixed layered sodium Trititanates. The dilation of interlayer space has further been proposed to occur due to inclusion of lithium ions in the interlayer space. The conductivity increases as the concentration of lithium increases. The increase of ionic conductivity in these compounds is due to accommodation of lithium ions with sodium ions in interlayer space.     

Effect of complexing salt on conductivity of PVC/PEO polymer blend electrolytes

Solid polymer electrolyte membrane comprising poly(vinyl chloride) (PVC), poly(ehylene oxide) (PEO) and different lithium salts (LiClO₄, LiBF₄ and LiCF₃SO₃) were prepared by the solution casting technique. The effect of complexing salt on the ionic conductivity of the PVC/PEO host polymer is discussed. Solid polymer electrolyte films were characterized by X-ray diffraction, FTIR spectroscopy, TG/DTA and ac impedance spectroscopic studies. The conductivity studies of these solid polymer electrolyte (SPE) films are carried out as a function of frequency at various temperatures ranging from 302 K to 353 K. The maximum room temperature ionic conductivity is found to be 0·079 × 10^?4 S cm^?1 for the film containing LiBF₄ as the complexing salt. The temperature dependence of the conductivity of polymer electrolyte films seems to obey the Vogel-Tamman-Fulcher (VTF) relation.     

Effect of annealing on the electrical and optical properties of V2O5-GeO2 glasses

Increases in the electrical conductivities of vanadium germanate glasses on annealing have been reported recently in the literature. The increases were attributed to the formation of microstructure on annealing. In the present work we report a study of the V₂O₅-GeO₂ glass system using electron paramagnetic resonance, optical absorption, differential scanning calorimetry and electron diffraction techniques. The V₂O₅-GeO₂ glass system consists of an equimolar mixture of vanadium pentoxide and germanium dioxide. One sample was unannealed and the other was annealed at 300° C for about 24 h. The results revealed that the increase in the electrical conductivity of the annealed samples could be attributed to the increase of reduced valence states of vanadium ions which accompany the microstructure formation and not solely to the structural change. Afzal Sheikh in electron diffraction studies is appreciated.     

Chemical insertion in the perovskite solid solutions Pr0.5+x−yLi0.5−3xBiy□2xTiO3: Implications on the electrical properties

Chemical insertion and de-insertion of lithium in pellet samples of the solid solutions Pr_0.5+x?yLi_0.5?3xBi_y□_2xTiO₃ were studied. Two regions of the phase diagram are studied: one having constant composition of bismuth and the other of lithium. The amount of inserted lithium depends on both the number of vacancies and the amount of bismuth in the original samples. The conductivity of the samples is directly related to the amount of inserted lithium and the activation energy depends on the unit cell volume. An analysis of the electronic and ionic components of the conductivity reveals that the untreated materials are pure ionic conductors, while after Li-insertion an additional electronic conductivity (t < 10^?2) occurs, due to a polaron mechanism, with an activation energy of 0.8 eV.     

Experimental study of the thermal conductivity of lithium vapor

The thermal conductivity of lithium vapor is measured. Equations are derived for calculation of the effective thermal conductivity and its components over a wide range of temperature and pressure.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 4, pp. 634–640, October, 1985.