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The formation of an electric double‐layer (EDL) is an important phenomenon for many research areas, including energy storage technology. Although EDL is well‐known in electrochemistry, most of the studies involve the characterization of liquid electrolyte/electrode interfaces, and only a limited number of studies in solid‐solid contacts, such as solid electrolyte/electrode interface are available. This paper employed electrochemical impedance spectroscopy (EIS) to systematically investigate the influence of experimental factors in the interfacial capacitance arising from the electrode polarization in a lithium disilicate glass/gold electrode interface. It analyzed the influence of a.c. input voltage amplitude, samples' roughness (mechanical and chemomechanical polishing) and thickness, range of applied frequency and temperature, and the number of impedance cycles. In short, it was found that an input voltage range of 15–60 mV is indicated to minimize potential electrochemical processes during electrode polarization, where the data is reproducible from the second measurement cycle onward. Smoother surfaces closely approximated ideal electrode spike behavior, with surface treatment exhibiting influence on interfacial capacitance values. Moreover, as expected, we observed an increase in relative permittivity values with increasing thickness, accompanied by decreased capacitance values. Finally, by employing optimal experimental conditions and analyzing the inflection frequency (finflection${{f}_{inflection}}$) of the ε′$\varepsilon ^{\prime}$ versus log(f$f$) curve, we determined that the ratio between effective charge carriers (ne${{n}_e}$) and the total number of charge carriers (nt${{n}_t}$) nent$\frac{{{{n}_e}}}{{{{n}_t}}}$ falls within the range of 5–12% between 130°C and 280°C. [ABSTRACT FROM AUTHOR]

The sodium ion–based materials have interesting physical properties which make them suitable for industrial applications. In this paper, we focus our work on sodium ytterbium phosphate NaYbP2O7, prepared by the solid-state method. It is found that NaYbP2O7 crystallizes in the monoclinic system with P121/n1 space group. Impedance analysis shows that this compound exhibits semiconductor behavior and that the conduction mechanism is thermally activated. AC conductivity measurements show that NaYbP2O7 can be a good ionic conductor with an activation energy value up to 0.94eV. The frequency dependence of conductivity is probably caused by the jump of Na ions between octahedral sites of the olive framework. Such properties of NaYbP2O7 make it suitable as an ionic conductor. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

MgO-doped partially stabilized zirconia (xMgPSZ, with x = 8 or 10 mol%) materials sintered at 1700°C, were characterized with respect to structure, microstructure, thermal expansion and electrical performance. The monoclinic (M) phase content is almost vestigial in 10MgPSZ, unlike in 8MgPSZ. Combined powder XRD and customized thermal expansion data analysis, allowed a separation between M and tetragonal (T) particles, outside or imbedded in cubic grains. Combination of thermal expansion and impedance spectroscopy data provided novel insights on the totally distinct roles of fine and dispersed T or M particles within the PSZ cubic matrix grains. [ABSTRACT FROM AUTHOR]

The design and production features of a solid oxide fuel cell greatly impact its microstructure and performance; however, these factors are frequently omitted in related studies. In this work, the influence of the design and formation factors of a solid oxide fuel cell on its performance and long-term stability is studied. The sintering process of multilayer half-cells is studied by heating microscopy and the optimal sintering strategy is identified. We show here the importance of the sintering strategy and suggest an approach for SOFC design that results in a stable in time performance. The electrochemical performance is evaluated by impedance spectroscopy and the distribution of relaxation times (DRT) technique. It is shown that the absence of the barrier layer leads to a decrease in the SOFC performance by 22.5% as-sintered and continues to drop down during the exposure of 850 °C for 400 h. The impregnation of the cathode and anode by Pr(NO3)3 and Ce(NO3)3 improves electrochemical performance by 15% and this increase withstands a heat treatment at least for 215 h without any noticeable degradation. The most stable in time performance of the cell with impregnated electrodes and the barrier layer is 515.3 mW × cm−2 (H2 + 3% H2O used as fuel, air + 3% H2O as oxidizer). [ABSTRACT FROM AUTHOR]

The Li content and anion lattice of Li 4 SiO 4 were modified to improve ionic conductivity. Li 2 CO 3 and Si 3 N 4 were mixed in a ratio of Li/Si = 4.5 and heated in NH 3 at 820 °C, which resulted in the formation of the oxynitride, Li 4.1 SiO 3.9 N 0.1 . Powder X-ray diffraction analyses revealed Li 4.1 SiO 3.9 N 0.1 and Li 4 SiO 4 to be isostructural with a subtle variation in the lattice constants. Diffuse-reflectance absorption spectroscopy, however, showed a significant decrease in the band gap, from 5.6 eV in Li 4 SiO 4 to 4.8 eV in Li 4.1 SiO 3.9 N 0.1 . X-ray photoelectron spectra of the Li 1 s and Si 2 p levels revealed enhanced lattice covalency in Li 4.1 SiO 3.9 N 0.1 compared to the oxide phase. The ionic conductivity of Li 4 SiO 4 and Li 4.1 SiO 3.9 N 0.1 were measured by ac impedance spectroscopy over the temperature range 100–400 °C. Non-linear fitting analysis of the equivalent circuit revealed that the ionic conductivity of Li 4.1 SiO 3.9 N 0.1 was approximately one order of magnitude higher than that of Li 4 SiO 4 . [ABSTRACT FROM AUTHOR]

The disk-shaped sintered compacts consisting mainly of c -axis-aligned lanthanum silicate oxyapatite (LSO) polycrystals doped with K 2 O and Al 2 O 3 were prepared by templated grain growth method. The tabular single crystals of K 2 O- and F-doped LSO were used as template particles, and the Al 2 O 3 -doped LSO as matrix powder. The chemical formula derived from the average chemical composition of the constituent LSO crystal grains was (La 9.60 K 0.16 □ 0.24) Σ=10 (Si 5.48 Al 0.38 □ 0.14) Σ=6 O 26 , where □ denotes vacancies in La and/or Si sites. One of the doped LSO grains was examined by single-crystal X-ray diffraction to confirm that the crystal structure was isomorphous to those previously reported. Other coexisting phases were 0.16 mol% LaAlO 3 and 0.34 mol% SiO 2 -rich interstitial material (probably in a liquid state at high temperature). With increasing temperature from 773 to 1073 K, the total oxide-ion conductivity (σ total) along the grain-alignment direction steadily increased from 1.31 × 10−4 to 3.21 × 10−3 S cm−1, each value of which was, at the same temperature, more than 7.7 times larger than that of the randomly grain-oriented polycrystal with the same bulk chemical composition. The larger σ total -value of the former polycrystal would be due to the significantly higher oxide-ion conductivity along the c -axis direction of the doped LSO. A solid oxide fuel cell (SOFC) using the textured polycrystal as the electrolyte was constructed and tested for power generation. The maximum power density was satisfactorily high at 873 K, indicating that the c -axis-aligned polycrystals of doped LSO would be potentially applicable as electrolytes for the SOFCs operating at medium to low temperatures. • Textured polycrystal of doped LSO successfully prepared by TGG method • Crystal structure of doped LSO is determined by single-crystal XRD • Grain alignment and doping effectively enhance the conductivity of LSO polycrystal • Textured polycrystal is potentially used as electrolytes of low-temperature SOFCs [ABSTRACT FROM AUTHOR]

In this manuscript, preparation, crystal structure and electrical properties of two types of A I M III (PO 3) 4 metaphosphates, namely LiCe(PO 3) 4 and LiPr(PO 3) 4 (monoclinic, C 2/ c), and NaCe(PO 3) 4 (monoclinic, P 2 1 / n) have been reported. All the compounds were prepared by conventional solid-state reaction and characterized by powder X-ray diffraction. The electrical properties of these materials were studied by impedance spectroscopy. The dc- conductivity (σ d c ) of all compounds show similar increasing trend with temperature and is attributed mainly to the alkali metal ion diffusion. However, a discontinuity in the temperature dependent σ d c is observed at higher temperature in all of them. The activation energy (eV) for alkali ion conductivity in LiCe(PO 3) 4 , LiPr(PO 3) 4 and NaCe(PO 3) 4 respectively, is 1.14, 1.18 and 0.84, up to certain temperature (∼973K), and increases to 1.31, 1.35 and 1.51 at higher temperature. The analysis of ac -conductivity and modulus spectra indicated a correlated movement of ions in the structure. It is observed that structure and electrical properties of these metaphosphates are dependent more on the nature and ionic radii of the alkali ions than the rare-earth ions. [Display omitted] • Structure & electrical properties of A I M III (PO 3) 4 (A = Li, Na; M = Ce, Pr) are studied. • Structure and electrical properties depend more on the AI than AIII ions. • The materials show appreciably higher alkali ion conductivity at high temperature. • A corelated movement of alkali ions in all these compounds is concluded. [ABSTRACT FROM AUTHOR]

The lithiation of tungsten bronze oxide β-SrTa 2 O 6 was accomplished by the solid state ion exchange of Sr 2+ → 2Li + , which led to a solid solution of Li x Sr 1−0.5 x Ta 2 O 6 ( x = 0–0.31). For the above conversion, β-SrTa 2 O 6 was reacted with various amounts of Li 2 CO 3 at 600 °C in air. With increasing x in Li x Sr 1−0.5 x Ta 2 O 6 , an orthorhombic-to-tetragonal symmetry transition was observed along with a gradual decrease in lattice volume. As observed from scanning electron microscopy and transmission electron microscopy, the grains of Li x Sr 1−0.5 x Ta 2 O 6 phases with x = 0.17 and 0.25 were formed from columnar bundles aligned along the c -axis. Solid state 7 Li nuclear magnetic resonance (NMR) spectroscopy revealed the presence of two different Li environments in Li x Sr 1−0.5 x Ta 2 O 6 , and their respective populations. The ionic conductivity of Li x Sr 1−0.5 x Ta 2 O 6 was measured by ac impedance spectroscopy as functions of the temperature and composition x . Regardless of the composition, the conductivity of Li x Sr 1−0.5 x Ta 2 O 6 displayed an Arrhenius type temperature dependence, and the highest Li + conductivity was found from x ≈ 0.17. At temperatures between 75 and 268 °C, the Li + ionic conductivity of Li 0.17 Sr 0.92 Ta 2 O 6 increased from 10 −8.8 S/cm to 10 −5.0 S/cm with an activation energy of 0.74 eV. [ABSTRACT FROM AUTHOR]

We present electrical conductivity measurements of BIFEVOX Bi4V2-xFexO11-y (0≤x≤0.9; 0≤y≤1), in which V (IV) ions have been systematically substituted by Fe (III) ions. Conductivity shows a power law frequency dependence described by the form σ*(ω)=σdc[1+(jω/ωp)n], known as universal dynamic response. Conversely, the electric modulus shows asymmetric peaks, characterized by stretched exponentials relaxation functions in time domain of the form φ(t)=exp(-(t/τσ)β). β is determined by the degree of correlation in the ionic motion. It´s value, β=0.56±0.03, is almost independent of temperature and iron content. Increasing Fe content leads to an exponential decrease of the conductivity and to an increase of the activation energy of the conduction process from 0.20 to 0.97 eV. These results are discussed in terms of oxygen vacancy ordering upon Fe (III) substitution.Presentamos medidas de la conductividad eléctrica del sistema BIFEVOX Bi4V2-xFexO11-y (0≤x≤0.9; 0≤y≤1), en el que se realiza la sustitución de iones V (IV) por Fe (III) de forma sistemática. La conductividad muestra un comportamiento potencial con la frecuencia, descrito por σ*(ω)=σdc[1+(jω/ωp)n], y conocido como respuesta dieléctrica universal. Análogamente, el módulo eléctrico presenta picos asimétricos, cuya función de relajación en el dominio del tiempo puede describirse mediante exponenciales “estiradas” de la forma φ(t)=exp(-(t/τσ)β). β da cuenta del grado de correlación del transporte iónico, siendo su valor, β=0.56±0.03, casi independiente de la temperatura y del contenido en Fe. Con el aumento en el contenido de Fe, la conductividad disminuye exponencialmente y la energía de activación del proceso de conducción aumenta de 0.20 a 0.97 eV. Estos resultados se discuten en términos de la ordenación de vacantes oxígeno al dopar con Fe (III).

Abstract: A theoretical model for quantifying the number of three phase boundary sites using the impedance spectrum of porous electrodes is presented and validated in exhaust gas sensors. The sensing responses and impedance spectra are registered before and after polarizing the sensors at high temperatures under different atmospheres and elapsed times. After polarizing under an oxidant atmosphere, the sensors do not modify their output response neither their impedance spectra. When polarizing for 3min at 680°C and under a reducing atmosphere, the sensing parameters improve (higher sensitivity and lower response times) and the impedance spectrum of the sensors changes. In this case, fitting with the proposed impedance model suggests that the number of three phase boundary sites in the electrode increases after polarizing. [Copyright &y& Elsevier]

Atomic force microscopy (AFM)-based impedance spectroscopy provides localized impedance information of materials and interfaces at the nanoscale by utilizing the conductive AFM tip as a moving electrode to detect current response as a function of time and frequency under controlled environments. This capability enables AFM-based nanoscale impedance measurements to play a unique role in enhancing our understanding of many electronic and electrochemical devices. This article introduces the central concepts of AFM-based impedance measurement and reviews recent examples applying this technique to a variety of functional materials systems, in particular focusing on fuel cells, lithium-ion batteries, photoactive biomembranes, as well as other application examples. [ABSTRACT FROM PUBLISHER]

Abstract: We report the first synthesis of pyrochlore-like Ln2TiO5 with Ln=Er–Lu via cooling at a rate as slow as 5°C/h in the range 1600–820°C. The materials thus prepared differ in structure from the oxygen-ion-conducting Ho2TiO5 pyrochlore: the X-ray diffraction patterns of the pyrochlore-like Ln2TiO5 (Ln=Er–Lu) show weak 511 and 531 pyrochlore superstructure peaks and an unidentified peak at 2θ =19.6° (Cu Kα) (5% intensity). The Ln2TiO5 (Ln=Er, Tm) pyrochlores prepared via very slow cooling followed by quenching in liquid nitrogen from 840°C contain, in addition to a pyrochlore-like phase, a small amount (up to 5%) of the low-conductivity high-temperature hexagonal phase β-Ln2TiO5. The pyrochlore Ho2TiO5 contains microdomains of the hexagonal phase β-Ho2TiO5, which does not affect its high oxygen ion conductivity. The conductivity of the pyrochlore-like Ln2TiO5 with Ln=Er and Yb is substantially lower than that of the fluorite-like Ln2TiO5 (Ln=Er, Yb) and oxygen-ion-conducting pyrochlore Ho2TiO5 obtained via furnace cooling (130°C/h), which can be understood in terms of oxygen ordering in these compounds and the presence of the low-conductivity high-temperature phase β-Ln2TiO5 in the pyrochlore-like Ln2TiO5 (Ln=Er, Yb) at measurement temperatures (∼500–840°C). [Copyright &y& Elsevier]

Glassy-crystalline composites have been prepared by infiltrating highly conducting silver vanadate glasses into diamond powder compacts. The process of infiltration was carried out at a high isostatic pressure (from 1.5 to 8 GPa) and temperatures up to 800 °C. The resulting composites have conductivities comparable to those of glasses used for infiltration, but exhibit a wider range of thermal stability (up to 300 °C) than glasses. Additionally, they have much better mechanical properties, in particular, being less brittle and exhibiting higher microhardness than glasses. [ABSTRACT FROM AUTHOR]

The system LiDyO2 has been prepared by solid state reaction method. X-ray diffractograms confirms the formation of the sample. The conductivity, impedance and modulus analysis of the samples have been carried out for different temperatures and frequencies. The bulk conductivity obtained from the impedance plot is found to be 1.7×10−5 Ω−1 cm−1 at 300 °C. The relaxation characteristics are discussed in terms of both the power law formalisms of the conductivity spectra and electrical modulus formalism. [Copyright &y& Elsevier]

Much of the research effort in the past decade has been closely focused on finding suitable solid electrolytes with high ionic conductivity for various applications. In this context, the compound Na 3 La(AsO 4) 2 was synthesized using the molten salt (flux) method and its structure was solved from the single-crystal X-ray diffraction data for the first time. Na 3 La(AsO 4) 2 crystallizes in the monoclinic space group P2 1 /c (#14) with a ​= ​19.451(4)Å; b ​= ​5.554(1)Å; c ​= ​14.365(3)Å; β ​= ​90.035(2)°. Its crystal structure consists of an open 3D network built of [LaO 8 ] polyhedra sharing oxygen corners and edges with neighboring [AsO 4 ] tetrahedra. Tunnels in the [010] direction accommodate Na+ cations. The ionic conductivity was investigated experimentally and computationally. High-temperature ac-conductivity measurements yielded the highest ionic conductivity of 1.93 ​× ​10−4 ​S ​cm−1 ​at 700 ​°C with the apparent activation energy E a ​= ​0.85eV. A complementary analysis through the bond valence site energy calculation (BVSE), revealed that the structure of Na 3 La(AsO 4) 2 favors a 3D ionic diffusion pathway with the empirical activation energy of 1.061 ​eV for the long-range migration of Na+ ions. 3D bond-valence sum energy maps of Na 3 La(AsO 4) 2 with all possible Na+ ​diffusion pathways. [Display omitted] • A novel arsenate Na 3 La(AsO 4) 2 was synthesized using the molten salt (flux) method. • Its crystal structure was determined by single-crystal X-ray diffraction. • The purity of the powder was verified by conventional Rietveld refinement. • The ionic conductivity of Na 3 La(AsO 4) 2 was probed by Electrochemical Impedance Spectroscopy (EIS). • Probable diffusion pathways of Na ​+ ​are simulated by means of Bond valence site energy (BVSE) model. [ABSTRACT FROM AUTHOR]