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Latest Articles Include:

• Editorial Board
  - Solid State Ionics 180():IFC (2009)
  
• Characterization of low temperature protonic conductivity in bulk nanocrystalline fully stabilized zirconia
  - Solid State Ionics 180():297-301 (2009)
  We investigated the conductivity of samples of bulk nanometric cubic yttria stabilized zirconia (YSZ 8%) with a grain size of about 16 nm and a relative density above 98%. In an oxygen atmosphere the material showed a large grain boundary resistivity. However, when exposed to a moist atmosphere at temperatures below 150 °C it showed a high conductivity, several orders of magnitude higher than the corresponding extrapolated ionic conductivity. A fairly high conductivity was measured even at room temperature. The conductivity was strongly dependent on the water partial pressure and showed a distinct isotopic effect, suggesting a protonic conductivity mechanism. This effect was not observed in samples with grain size above 50 nm, suggesting the possibility that nanostructure can induce drastic modification in the conduction mechanism of ceramic electrolytes.
• Mechanically induced decrease of the Li conductivity in an alumosilicate glass
  - Solid State Ionics 180():302-307 (2009)
  In the present work β-spodumene LiAlSi2O6 and the corresponding glass form a model system highly suitable to study the influence of particle size on Li ion dynamics. The nanostructured samples were prepared by high-energy ball milling of the coarse grained starting material and the corresponding glass, respectively. Diffusion parameters and electrical conductivity were measured by 7Li spin-lattice relaxation nuclear magnetic resonance (NMR) and impedance spectroscopy. As reported previously, the Li diffusivity in the glassy sample is larger than that in the coarse grained crystalline material of the same chemical composition [Franke et al., Ber. Bunsenges. Phys. Chem. 96, 1674 (1992).] which is quite often observed also for other materials. Decreasing the particle size down to the nm-regime causes an enhancement of the Li conductivity of β-spodumene LiAlSi2O6 reaching an upper limit which is, however, still lower than the conductivity of the corresponding glass. Surp! risingly, when the glassy material is mechanically treated under the same conditions, the Li diffusivity is slowed down. The Li conductivity of such a sample resembles that of nanocrystalline LiAlSi2O6. This is astonishing since one might expect that mechanical treatment of a glassy sample does not further influence the transport parameters. A possible structural description trying to explain the observed convergence of the transport parameters of the crystalline and glassy materials as a result of milling is briefly presented.
• Evolution of the electrochemical processes vs. Li in RuO2 as a function of crystallite size
  - Solid State Ionics 180():308-313 (2009)
  Rutile-type RuO2 powders with different crystallite sizes were obtained by annealing of a nanometric precursor, prepared by a precipitation method, at different temperatures. The effect of crystallite size on the electrochemical Li-intercalation reactivity has been studied. For this type of material the size decrease is detrimental as parasitic reactions become prominent. Furthermore, for samples with crystallite size from 3 to 40 nm, the reaction still proceeds through a triphasic process as underlined by PITT and in situ XRD measurements.
• Quantification of local oxygen defects around Yttrium ions for yttria-doped ceria–zirconia ternary system
  - Solid State Ionics 180():314-319 (2009)
  Local coordination structure around Yttrium ions in CeO2–Y2O3 binary and [(CeO2)x(ZrO2)1−x]0.8(YO1.5)0.2 (x = 0.0 ~ 1.0) ternary system has been investigated by 89Y MAS-NMR. NMR spectra are found to be consisted of multiple peaks that can be assigned to 6-, 7- and 8-oxygen coordinated Yttrium ions. Compositional dependence of the spectrum was observed and compared with the previous results for ZrO2–Y2O3 binary system. The present investigation suggested the degree of localization of the oxygen vacancy around the cation is in the order of Zr4+ > Y3+ > Ce4+. The degree of the oxygen vacancy preference for each cation was quantitatively determined for CeO2–ZrO2–Y2O3 ternary system the first time.
• Anisotropic properties in textured lead barium niobate compositions around the morphotropic phase boundary
  - Solid State Ionics 180():320-325 (2009)
  Partially textured PbxBa1 − xNb2O6 ceramics, with compositions around the morphotropic phase boundary, were obtained by the hot forging technique. Scanning electron microscopy revealed that the grains were arranged with their lengthwise direction preferentially in the direction of the forging. From the differences of the X ray diffraction profiles between the samples analyzed in the direction of forging and those analyzed in the pressing direction it was possible to confirm the crystallographic growth habit of the PBN ceramics for the tetragonal and orthorhombic symmetry compositions. The identification of a mixture of tetragonal and orthorhombic symmetry phases in a whole range of studied compositions was also possible. The phase transformation around the morphotropic phase boundary (in this case, tetragonal (4mm) to orthorhombic (m2m)) could be analyzed through the direction change of the polarization vector in partially textured PBN ceramics.
• Conductivity relaxation patterns of mixed conductor oxides under a chemical potential gradient
  - Solid State Ionics 180():326-337 (2009)
  Chemical diffusivity of a mixed ionic–electronic conductor compound is often measured by monitoring the relaxation of electrical conductivity with time under a component's chemical potential gradient. Conductivity relaxations were systematically examined on undoped polycrystal BaTiO3, acceptor-doped polycrystal BaTiO3, donor-doped polycrystal BaTiO3, and undoped single crystal TiO2 upon oxidation and reduction, and on proton-conducting, acceptor-doped polycrystal SrCeO3 and BaCeO3 upon oxidation/reduction or hydration/dehydration at elevated temperatures. It has been found that there are three patterns of relaxation: single-fold (single relaxation time) monotonic, twofold (two relaxation times) monotonic and twofold non-monotonic relaxation. The inner working for each pattern is discussed and a general solution to the relaxations is presented in closed form, together with the chemical diffusivities as evaluated thereby.
• Structure, defect chemistry, and proton conductivity in nominally Sr-doped Ba3La(PO4)3
  - Solid State Ionics 180():338-342 (2009)
  The AC conductivity of eulytite-structured Ba3La(PO4)3 with 2 mol% Sr substituted for La has been investigated in the range 300–1300 °C at different oxygen and water vapor (H2O or D2O) partial pressures. The overall sample impedance has contributions from bulk (grain interior) and grain boundaries. It is concluded from the H/D isotope effect that the bulk conductivity is mainly protonic. The defect chemistry leading to a content of protons is discussed.
• Proton conductivity of Al(H2PO4)3–H3PO4 composites at intermediate temperature
  - Solid State Ionics 180():343-350 (2009)
  Composites of Al(H2PO4)3 and H3PO4 were synthesised by soft chemical methods with different Al/P ratios. The Al(H2PO4)3 obtained was found to have a hexagonal symmetry with parameter a = 13.687(3)Å, c = 9.1328(1)Å. The conductivity of this material was measured by a.c. impedance spectroscopy between 100 °C and 200 °C in different atmospheres. The conductivity of pure Al(H2PO4)3 in air is in the order of 10− 6–10− 7 S/cm between 100 and 200 °C. For samples containing small excess of H3PO4, much higher conductivity was observed. The impedance responses of the composites were found to be similar with AlH2P3O10·nH2O under different relative humidity. The conductivity of Al(H2PO4)3–H3PO4 composite with Al/P = 1/3.5 reached 6.6 mS/cm at 200 °C in wet 5% H2. The extra acid is found to play a key role in enhancing the conductivity of Al(H2PO4)3–H3PO4 composite at the surface region of the Al(H2PO4)3 in a core shell type behaviour. 0.7% excess of H3PO4 can incr! ease the conductivity by three orders of magnitude. These composites might be alternative electrolytes for intermediate temperature fuel cells and other electrochemical devices. Conductivity (9.5 mS/cm) changed little, when the sample was held at 175 °C for over 100 h as the conductivity stabilised.
• Structure of Na2S–GeS2 glasses studied by using neutron and X-ray diffraction and reverse Monte Carlo modeling
  - Solid State Ionics 180():351-355 (2009)
  Neutron and X-ray diffraction measurements were performed to investigate the structure of Na2S–GeS2 glasses synthesized by mechanical alloying. The Ge–S coordination numbers calculated from the total correlation functions show that GeS4 tetrahedra form the basic framework structure of Na2S–GeS2 glasses. In addition, a three-dimensional structural model of the (Na2S)50(GeS2)50 glass was obtained by using reverse Monte Carlo (RMC) simulation on neutron and X-ray diffraction data, and it was compared with the RMC model previously obtained for a (Li2S)50(GeS2)50 glass. The results show that the Ge–S framework structures in the two glasses are almost the same in the short and intermediate ranges; that is, the Ge–S framework structures are formed mainly by the connection of corner-sharing GeS4 tetrahedra. Many of the Na ions are coordinated by four S atoms, which are non-bridging S atoms and/or bridging S atoms.
• Conductivity and dielectric relaxation phenomena in (NH4)2SO4 single crystal
  - Solid State Ionics 180():356-361 (2009)
  AC impedance measurements have been carried out on (NH4)2SO4 single crystals for the temperatures from 300 to 473 K and frequency range between 100 Hz and 4 MHz. The results reveal two distinct relaxation processes in the sample crystal. One is the dipolar relaxation with a peak at frequency slightly higher than 4 × 106 Hz. The other is the charge carrier relaxation at lower frequencies. The frequency dependence of conductivity is described by the relation σ(ω) = Bωn, and n = 1.32 is obtained at temperatures below 413 K. This value drops to 0.2 and then decreases slightly with increasing temperature. The dipolar response of the (NH4)2SO4 single crystal under an ac field is attributed to the reorientation of dipoles. The contribution of charge carriers is increasing substantially with increasing temperature at temperatures above 413 K. The temperature variation of conductivity relaxation peaks follows the Arrhenius relation. The obtained activation energy for migrat! ion of the mobile ions for (NH4)2SO4 single crystal was 1.24 eV in the temperature range between 433 and 468 K in this intrinsic region. It is proposed that the NH4+ in the sample crystal has the contribution to the electrical conduction.
• Effect of thermal history and characterization of plasticized, composite polymer electrolyte based on PEO and tetrapropylammonium iodide salt (Pr4N+I-)
  - Solid State Ionics 180():362-367 (2009)
  The search for anionic conductors based on solid polymer electrolytes is important for the development of photo-electrochemical (PEC) solar cells due to their many favourable chemical and physical properties. Although solid polymer electrolytes have been extensively studied as cation, mainly lithium ion, conductors for applications in secondary batteries, their use as anionic conductors have not been studied in greater detail. In a previous paper we reported the application of a PEO based iodide ion conducting electrolyte in a PEC solar cell. This electrolyte had the composition PEO: Pr4N+I− = 9:1 with 50 wt.% ethylene carbonate (EC). In this work we have studied the effect of incorporating alumina filler on the properties of this electrolyte. The investigation was extended to electrical and dielectric measurements including high frequency impedance spectroscopy and thermal analysis. In the DSC themograms two endothermic peaks have been observed on heating, one of these peaks is attributed with the melting of the PEO crystallites, while the other peak with a melting temperature ~ 30 °C is attributed to the melting of the EC rich phase. The melting temperature of both these peaks shows a marked variation with alumina content in the electrolyte. The temperature dependence of the conductivity shows that there is an abrupt conductivity increase in the first heating run evidently due to the melting of the EC rich phase. High conductivity values are retained at lower temperatures in the second heating. Conductivity isotherms show the existence of two maxima, one at ~ 5% Al2O3 content and the other at ~ 15%. The occurrence of these two maxima has been explained in terms of the interactions caused by alumina grains, the crystallinity and melting of the PEO rich phase. As seen from latent heat of melting, the crystallinity of the electrolyte has reduced consider! ably during the first heating run. In contrast to the conductivity enhancement caused by ceramic fillers in PEO-based cation containing electrolytes, no conductivity enhancement has been observed in the present PEO based anionic conducting materials by adding alumina except at low temperatures.
• Oxygen nonstoichiometry and defect equilibrium in La2 − xSrxNiO4 + δ
  - Solid State Ionics 180():368-376 (2009)
  Nonstoichiometric variation of oxygen content in La2 − xSrxNiO4 + δ (x = 0, 0.1, 0.2, 0.3, 0.4) and decomposition P(O2) were determined by means of high temperature gravimetry and coulometric titration. The measurements were carried out in the temperature range between 873 and 1173 K and the P(O2) range between 10− 20 and 1 bar. La2 − xSrxNiO4 + δ showed the oxygen excess and the oxygen deficient compositions depending on P(O2), temperature, and the Sr content. The value of partial molar enthalpy of oxygen approaches zero as δ increases in the oxygen excess region, which indicate that the interstitial oxygen formation reaction is suppressed as δ increase. The relationship between δ and logP(O2) were analyzed by two types of defect equilibrium models. One is a localized electron model, and the other is a delocalized electron model. Both models can well explain the oxygen nonstoichiometry of La2 − xSrxNiO4 + δ with a regular solution approximation.
• The study of novel multi-doped spinel Li1.15Mn1.96Co0.03Gd0.01O4 + δ as cathode material for Li-ion rechargeable batteries
  - Solid State Ionics 180():377-380 (2009)
  Novel spinel Li1.15Mn1.96Co0.03Gd0.01O4 + δ was synthesized by high temperature solid-state reaction method. The product was identified as well-defined spinel phase by X-ray diffraction (XRD); the SEM images illustrated that the particle distribution was well-proportioned. The initial special capacity was 126.5 and 128.1 mAh g− 1 at 25 and 50 °C. The fading rate was 0.017% and 0.098% per cycle under 0.5 °C at 25 and 50 °C, respectively. The results showed that Li1.15Mn1.96Co0.03Gd0.01O4 + δ displayed excellent capacity and cycleability.
• Lithium insertion behavior of carbon nanowalls by dc plasma CVD and its heat-treatment effect
  - Solid State Ionics 180():381-385 (2009)
  Lithium insertion behavior of carbon nanowall (CNW), which is a two-dimensional carbon nanostructures, was studied by cyclic voltammetry and charge/discharge measurements. It was found that CNW had reversible capacities of more than 200 mAh/g with stable charge/discharge potential like that of graphite even though the materials were produced at low temperature of 973 K. It was also found that CNW showed good responses of lithium insertion/extraction reaction because of their small and uniform particle size with well oriented graphene in nanometer scale. Heat treatment of CNW was found to purify the CNW from by-product amorphous carbon phase and the effect on their charge/discharge property was also clarified.
• Rapid synthesis of LiFePO4/C composite by microwave method
  - Solid State Ionics 180():386-391 (2009)
  A highly crystalline LiFePO4/C phase was successfully synthesized by a microwave irradiation method in 4 min. SEM and particle size analysis indicate that the particle size of resulting LiFePO4/C is much smaller than that of the solid-state derived sample and that it mostly distributes in the range of 160–600 nm. Cycling tests show that the sample prepared by microwave method can deliver 150 mAh g− 1 at 17 mA g− 1(0.1C). Further AC impedance measurements reveal that the LiFePO4 electrode can be well activated after the first cycle as reflected by the dramatic decrease in the charge transfer resistance.
• New nanocomposite polymer electrolyte comprising nanosized ZnAl2O4 with a mesopore network and PEO-LiClO4
  - Solid State Ionics 180():392-397 (2009)
  A novel poly(ethylene oxide) (PEO)-based nanocomposite polymer electrolyte (NCPE) has been developed by using nanosized, high surface area ZnAl2O4 with a mesopore network as the filler. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM) were used to characterize the NCPE. The results showed that the presence of the nanosized ZnAl2O4 powder leads to a reduction in the crystallinity of the PEO phase. The ionic conductivity and lithium ion transference number of the PEO-based polymer electrolyte were enhanced by the addition of the nanosized ZnAl2O4 powder. A broad electrochemical stability window suggests that the PEO-LiClO4-ZnAl2O4 NCPE is a viable candidate for the electrolyte material in lithium polymer batteries.
• Structural and electrochemical properties of LiNi0.5Mn0.5 − xAlxO2 (x = 0, 0.02, 0.05, 0.08, and 0.1) cathode materials for lithium-ion batteries
  - Solid State Ionics 180():398-404 (2009)
  Layered LiNi0.5Mn0.5 − xAlxO2 (x = 0, 0.02, 0.05, 0.08, and 0.1) series cathode materials for lithium-ion batteries were synthesized by a combination technique of co-precipitation and solid-state reaction, and the structural, morphological, and electrochemical properties were examined by XRD, FT-IR, XPS, SEM, CV, EIS, and charge–discharge tests. It is proven that the aliovalent substitution of Al for Mn promoted the formation of LiNi0.5Mn0.5 − xAlxO2 structures and induced an increase in the average oxidation number of Ni, thereby leading to the shrinkage of the lattice volume. Among the LiNi0.5Mn0.5 − xAlxO2 materials, the material with x = 0.05 shows the best cyclability and rate ability, with discharge capacities of 219, 169, 155, and 129 mAh g− 1 at 10, 100, 200, and 400 mA g− 1 current density respectively. Cycled under 40 mA g− 1 in 2.8–4.6 V, LiNi0. 5Mn0.45Al0.05O2 shows the highest discharge capacity of about 199 mAh g− 1 for the first cycle, ! and 179 mAh g− 1 after 40 cycles, with a capacity retention of 90%. EIS analyses of the electrode materials at pristine state and state after first charge to 4.6 V indicate that the observed higher current rate capability of LiNi0. 5Mn0.45Al0.05O2 can be understood due to the better charge transfer kinetics.
• The investigation of electrochemical properties and ionic motion of functionalized copolymer electrolytes based on polysiloxane
  - Solid State Ionics 180():405-411 (2009)
  The effect of EO side chain functionalization on the transport and electrochemical properties of polysiloxane electrolytes has been examined in this report. First, a study of the electrochemical stability of the electrolytes by linear sweep voltammetry shows that the polymer electrolytes have a negligible effect on the electrolyte stability windows. In addition, the parameters of cation mobility in polysiloxane electrolytes, such as ionic transference numbers and diffusion coefficients, were increased by increasing the lengths of the EO side chain. However, cation mobility in polymer structures is quite different compared to liquid-based systems and is probably suppressed, resulting in their polymer structure. Therefore, Positron Annihilation Lifetime Spectroscopy (PALS) was used to study the relationship between orthopositronium (o-Ps) lifetime, free volume radius, free volume of micro voids and EO side chain affection at different temperatures. Finally, a battery app! lication with LiCoO2 and LiFePO4/polymer electrolyte/lithium metal electrode was monitored for its potential use in the future.
• A ceria layer as diffusion barrier between LAMOX and lanthanum strontium cobalt ferrite along with the impedance analysis
  - Solid State Ionics 180():412-417 (2009)
  A thin interlayer of samarium doped ceria (SDC) is applied as diffusion barrier between La1 − xSrxCoyFe1 − yO3x = 0.1–0.4, y = 0.2–0.8 (LSCF) cathode and La1.8Dy0.2Mo1.6W0.4O9 (LDMW82) electrolyte to obstruct Mo–Sr diffusion and solid state reaction in the intermediate temperature range of SOFC. We demonstrate the effectiveness of the diffusion barrier through contrasting the clearly defined interfaces of LSCF/SDC/LDMW82 against a rugged growing product layer of LSCF/LDMW82 in 800 °C thermal annealing, and analyze the product composition and the probable new phase. In addition, the measured polarization resistance is considerably lower for the half-cell with a diffusion barrier. Therefore, the electrochemical performance of the LSCF cathode is investigated on the SDC-protected LDMW82. The cell with LSCF (x = 0.4) persistently outperforms the one with x = 0.2 in polarization resistance because of its small low-frequency contribution. The activation energy of ! polarization resistance is also lower for La0.6Sr0.4CoyFe1 − yO3 (112–135 kJ/mol), than that for La0.8Sr0.2CoyFe1 − yO3 (156–164 kJ/mol). La0.6Sr0.4CoyFe1 − yO3y = 0.4–0.8 is the proper composition for the cathode interfaced to SDC/LDMW82.
• Element interdiffusion at electrolyte–cathode interfaces in ceramic high-temperature fuel cells
  - Solid State Ionics 180():418-423 (2009)
  Ceramic high-temperature fuels cells (or solid-oxide fuel cells, SOFCs) directly convert hydrogen and also hydrocarbons into electrical energy. Recently developed functional materials to be used as cathodes show excellent performance, but they suffer from interfacial reactions with adjacent layers. These reactions lead to a rapid degradation of the fuel cells which limits their potential for application. Therefore, these reactions must be prevented by protective interlayer coatings, for instance by a ceramic (Ce,Gd)O2-δ (CGO) diffusion barrier. This paper discusses selected cathode–interlayer–electrolyte interdiffusion phenomena analysed by transmission electron microscopy (TEM). Different techniques for the application of the CGO diffusion barrier screen-printing and subsequent sintering, and physical vapour deposition–were employed to probe the influence of the processing on the diffusion of chemical species from the functional layers. Moreover, some model exp! eriments were carried out to evaluate the significance of element diffusion on the power density.
• Synthesis and characterization of nanoparticulate films for intermediate temperature solid oxide fuel cells
  - Solid State Ionics 180():424-430 (2009)
  Nanocrystalline strontium-doped lanthanum manganite (LSM) with a high specific surface area of 70 m2/g was synthesized via spray pyrolysis. The as prepared powder was characterized by ex-situ X-ray diffraction (XRD), in-situ high temperature X-ray diffraction (HTXRD), ex-situ nitrogen adsorption and high resolution scanning electron microscopy (HRSEM). LSM nanopowders with a mean particle size of 40 nm were dispersed in water-based media using ultrasonication. Nanocomposite LSM-GDC (gadolinium doped ceria) thin films were prepared by single step spin coating of co-stabilized LSM and GDC dispersions. The thickness of these thin films (≤ 1 μm) is more than 10 times lower than conventional cathode layers prepared by screen printing. The interfacial polarization resistances were 68, 118 and 220 mΩ cm2 at 850, 800 and 750 °C, respectively. The high performance is attributed to small grain size, high porosity and large specific surface area. This method offers a very co! st effective approach for the preparation of electrochemically highly active porous thin films, particularly applicable for micro solid oxide fuel cells.
• Three-phase-boundary dynamics at the Ni/ScYSZ interface
  - Solid State Ionics 180():431-438 (2009)
  Chronoamperometry using a three-electrode cell configuration was undertaken with a nickel point-electrode acting as the working electrode on a polished ScYSZ electrolyte in a hydrogen atmosphere at 750–850 °C. High anodic overpotentials resulted in the occurrence of distinct sawtooth oscillation patterns in the measured current signal. The current oscillations indicated that a dynamic electrode process was taking place. Decreasing the water content in the measurement atmosphere as well as lowering the applied anodic overpotential had the effect of lowering the frequency and the amplitude of the current oscillations. A mechanism accounting for the observed phenomena and possible implications for solid oxide fuel cell operation are presented.
• Calendar
  - Solid State Ionics 180():439-440 (2009)