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Li0.4La0.56TiO3 (LLTO) lithium-ion conducting solid electrolyte has been synthesized by aqueous sol-gel synthesis method. The free standing and alumina substrate supported thick films have been prepared from the obtained powder by tape casting. The films and bulk ceramics were studied by impedance spectroscopy in the frequency range from 10 Hz to 10 GHz. The equivalent circuit modelling was implemented in order to determine the electrical parameters of LLTO films and ceramics. The free standing LLTO films grain conductivity was found to be similar to the one of ceramic sample, while the grain boundary conductivity of the free standing film was slightly higher compared to LLTO ceramics.

Comparative studies of the physicochemical and electrochemical properties of BaCe0.9Y0.1O3 and Ba0.95Ca0.05Ce0.9Y0.1O3 sintered ceramics are described. The orthorhombic (Pnma) space group was determined for both investigated samples within the temperature range 25–800 °C, using the X-ray diffraction method. A decrease in the cell volume of Ba0.95Ca0.05Ce0.9Y0.1O3 compared to that of BaCe0.9Y0.1O3 was observed within the investigated temperature range. It was found that the partial substitution of calcium for barium, resulting in Ba0.95Ca0.05Ce0.9Y0.1O3, caused an increase in specific free volume and global instability index compared to the original composition BaCe0.9Y0.1O3. Improvement of the chemical resistance of Ba0.95Ca0.05Ce0.9Y0.1O3 in a CO2 gas atmosphere was observed. It was found that Ba0.95Ca0.05Ce0.9Y0.1O3 exhibited a slightly lower level of electrical conductivity than BaCe0.9Y0.1O3 in air as well as in Ar H2 gas atmospheres. The greater chemical resistance of Ba0.95Ca0.05Ce0.9Y0.1O3 in a CO2 gas atmosphere enhances the suitability of the modified material as an electrolyte for fuel cells with proton-conducting ceramics. The electrochemical response of the interface (La0.60Sr0.40)0.95Co0.20Fe0.80O3−δ|Ba0.95Ca0.05Ce0.9Y0.1O3 was also investigated within the applied potential range from −0.05 to −0.5 V in SOFC mode as well as from 0.05 to 0.5 V in SOEC mode); it was found that the current reached a fairly stable value over time.

Single crystals of (Cu1-хAgx)7GeS5I solid solutions were grown by vertical zone crystallization method. XRD studies have shown that they crystallize in face-centered cubic lattice of the argyrodite structure (space group F 4 ¯ 3 m , Z = 4). Structural studies were performed on the basis of original structure model by means of Rietveld refinement method. Electrical measurements were carried out in the temperature interval 300–360 K and in the range of frequencies 10 Hz–10 GHz. Temperature and frequency dependences of electrical conductivity were analyzed. Influence of cation substitution on the electrical conductivity as well as relationship between structural and electrical properties of (Cu1-хAgx)7GeS5I solid solutions were studied.

Comparative studies were performed on variations in the ABO3 perovskite structure, chemical stability in a CO2-H2 gas atmosphere, and electrical conductivity measurements in air, hydrogen, and humidity-involving gas atmospheres of monophase orthorhombic Ba1−xSrxCe0.9Y0.1O3−δ samples, where 0 < x < 0.1. The substitution of strontium with barium resulting in Ba1−xSrxCe0.9Y0.1O3−δ led to an increase in the specific free volume and global instability index when compared to BaCe0.9Y0.1O3−δ. Reductions in the tolerance factor and cell volume were found with increases in the value of x in Ba1−xSrxCe0.9Y0.1O3−δ. Based on the thermogravimetric studies performed for Ba1−xSrxCe0.9Y0.1O3−δ, where 0 < x < 0.1, it was found that modified samples of this type exhibited superior chemical resistance in a CO2 gas atmosphere when compared to BaCe0.9Y0.1O3−δ. The application of broadband impedance spectroscopy enabled the determination of the bulk and grain boundary conductivity of Ba1−xSrxCe0.9Y0.1O3−δ samples within the temperature range 25–730 °C. It was found that Ba0.98Sr0.02Ce0.9Y0.1O3−δ exhibited a slightly higher grain interior and grain boundary conductivity when compared to BaCe0.9Y0.1O3−δ. The Ba0.95Sr0.05Ce0.9Y0.1O3−δ sample also exhibited improved electrical conductivity in hydrogen gas atmospheres or atmospheres involving humidity. The greater chemical resistance of Ba1−xSrxCe0.9Y0.1O3−δ, where x = 0.02 or 0.05, in a CO2 gas atmosphere is desirable for application in proton ceramic fuel cells supplied by rich hydrogen processing gases.

The lanthanum strontium cobalt ferrite (LSCF)-Ag composite cathode material was prepared in aqueous solution by new one-step method. In this method silver nanoparticles obtained by the reduction of [Ag(NH3)2]+ complex with sucrose were directly deposited onto the surface of LSCF powder. UV–Vis spectra of supernatant solution taken during synthesis showed the presence of a sharp excitation band near 397 nm attributed to the surface plasmon excitation of silver nanoparticles. Obtained composite powder was sintered to samaria doped ceria electrolyte in one step sintering procedure at 1000 °C. The presence of silver in LSCF cathode facilitates the oxygen reduction. The comparison of impedance spectra of LSCF-Ag cathodes with spectra reported in literature for similar LSCF cathodes shows that this effect is important at lower oxygen partial pressures. The analysis of the electrochemical impedance spectra recorded in the range 10−2–1010 Hz reveals that the second high frequency semicircle ascribed to the electrolyte grain boundary impedance is distorted due to process belonging to oxygen reduction reaction.

The gadolinia-doped ceria (GDC) thin films were deposited by pulsed laser deposition. Samples with special geometry were prepared which allowed us to characterize GDC film in across-plane direction. The electrical properties of the films were investigated by means of impedance spectroscopy in the frequency range of 10 Hz to 10 GHz and 380–600 K temperature interval. The data analysis was performed by using appropriate equivalent circuit. The equivalent circuit modeled thin GDC film itself, platinum metal connections (traces) in the dielectric medium of sapphire substrate and interfaces between the film and platinum electrodes. Hence, several factors influenced the impedance spectra, namely the properties of substrate, the oxygen-ion transport in the film, ion blocking at the interface between the film and the electrode, and metal traces. The electrical properties of GDC thin films were compared with these of bulk ceramics and showed similar conductivity and dielectric permittivity values. The study also revealed that measurement data at electrical field frequencies of up to 10 GHz were particularly important to correctly estimate electrical properties of GDC thin films, because at high temperatures the electric response of GDC film shifts to high frequencies (higher than 1 MHz at 600 K). The thin film sample preparation for high frequency measurements and fitting of impedance data by using relatively simple equivalent circuit model is presented.

International audience; Na2MnP2O7 is a promising sodium-ion battery cathode material. In our work we analyse electrical properties of Na2MnP2O7 ceramics by impedance spectroscopy in the broad frequency range from 10 Hz to 10 GHz. Temperature dependencies of conductivity indicated a phase transition taking place in the grains of ceramics at 663 K, which was also evidenced by differential thermal analysis and thermal X-ray diffraction. In addition, close to the room temperature protonic conductivity strongly influences the total conductivity of the ceramics. Both newly observed phenomena may be important for overall sodium battery performance.

NaCsZn 0.5 Mn 0.5 P 2 O 7 powders were prepared by solid state reaction method. The study of the powder structure was conducted by X-ray diffraction (XRD) in temperature range from room temperature (RT) to 700 K. Rietveld analysis of XRD patterns showed that obtained NaCsZn 0.5 Mn 0.5 P 2 O 7 is a mix of three phases: orthorhombic (s.g. Cmc 2 1 ) NaCsMnP 2 O 7 , monoclinic (s.g. P 2 1 /n) NaCsZnP 2 O 7 and monoclinic (s.g. P 2 1 /n) Cs 2 MnP 4 O 12 . In the temperature ranges (400–500) K and (500–600) K the anomalies of lattice parameters for the NaCsMnP 2 O 7 and Cs 2 MnP 4 O 12 phases respectively were found. The electrical properties of the sintered ceramics were investigated from RT to 700 K and in the frequency range 10–3 × 10 9 Hz. The anomalies of electrical conductivity, dielectric permittivity and dielectric losses in investigated temperature ranges in these ceramics were found. This phenomenon can be associated with disordering in the lattices of NaCsMnP 2 O 7 and Cs 2 MnP 4 O 12 compounds.

Pure perovskite structure Li 0.5 − y Na y La 0.5 Nb 2 O 6 compounds with y values of 0, 0.1, 0.2, 0.3, 0.4, 0.43, 0.48 and 0.5 have been synthesized. Ceramics of these compounds were studied by X-ray diffraction and impedance spectroscopy in the frequency range of 10 Hz to 10 GHz and temperature interval from 300 K to 800 K. The linear increase of the lattice parameters with increasing temperature causes the wider opening of bottleneck for lithium migration which leads to ionic conductivity increase. The temperature dependencies of the studied compounds conductivity were described by modified Vogel–Fulcher–Tammann equation. The influence of Li + to Na + substitution to the lithium ionic transport is also analysed. On one hand the lattice parameters of Li 0.5 − y Na y La 0.5 Nb 2 O 6 were found to be bigger for compound with higher sodium concentration, which also increases their ionic conductivity. On the other hand the increase of y leads to decrease of charge carriers, which are lithium ions, concentration. Consequently the conductivity rapidly decreases.

Silver is one of the most promising cathode materials for low temperature (300–500 °C) solid oxide fuel cells. The most important disadvantage of silver is its migration in the electric field. For better understanding of this phenomenon, an in situ observation of the migration mechanism was undertaken with the use of high-temperature microscopes. Scandia stabilised ceria doped zirconia CeScSZ electrolyte prepared from commercial powder was examined before and after silver migration experiments using scanning electron microscope. X-ray diffraction, broadband electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. The silver electrodes for solid oxide fuel cells were prepared using magnetron sputtering. The described cells under polarisation were examined using a high-temperature low energy electron microscope. Reference cells and post-mortem cells were observed using a scanning electron microscope equipped with high temperature stage. Under polarisation, silver moved inside the electrolyte and along the surface towards the region between electrodes. The structures thus formed were similar to those previously described in the literature; however, direct observation of the deposit growth was unsuccessful. In situ scanning electron microscopy observations of the silver electrode at 650 °C revealed neither melting of the smallest silver particles nor movement of silver structures. Silver migration through the electrolyte caused a reduction in grain interior conductivity of the electrolyte, whereas its grain boundary conductivity remained unaffected.

International audience; Often the paramagnetic defects have important impact on the nuclear relaxation even in the “nominally” pure samples. These effects show themselves either by the nearest-neighbors only or by the dipolar long-range interaction. The former are addressed in this paper in which we built a model for calculation of T1, T1Q, T2, T1ρ when there is—or not—a residual quadrupolar interaction. This model shows that the maxima of R2 = 1/T2 and R1ρ = 1/T1ρ are shifted toward the low frequencies (low temperatures with regards to the one of R1 = 1/T1), the maximum of R1ρ is shifted toward the low frequencies with regards to the one of R2, and this model is general and can be applied to any system which relaxes by transferred hyperfine interaction. This model was applied to Li1.3Al0.3Ti1.7(PO4)3. It accounts for all the experimental results of T1 (6Li), T1 (7Li), T1Q (7Li), T2 (7Li), and T1ρ (7Li) which were used to highlight local dynamic properties of the lithium versus temperature. The analysis of these results allows us to conclude that inside the natrium superionic conductor (NASICON) framework the lithium undergoes an anisotropic motion, evidenced both with the residual quadrupolar interaction and the measures of the relaxation times, and the relaxation of the lithium is mainly due to the hyperfine transferred fluctuations. Thus, the motion drives the lithium ions in the neighborhood of the oxygens, and these dynamical results allow confirming structural aspects concerning the conducting pathways.

Gadolinium doped ceria (GDC) has been investigated as a promising material for application as an electrolyte in intermediate temperature solid oxide fuel cells (IT-SOFC). In this work, 10GDC powders (Gd 0.1 Ce 0.9 O 1.95 ) were synthesized by sol–gel combustion and sol–gel synthesis routes using the same complexing agents in both procedures. The thermal behavior of Gd–Ce–O precursor gels was investigated by TG–DSC measurements. X-ray diffraction (XRD) analysis was used for the characterization of phase purity and crystallinity of synthesized samples. Scanning electron microscopy (SEM) was employed for the estimation of surface morphological features. Nitrogen adsorption–desorption (BET model) was used for evaluation of specific surface area. The surface composition was determined by X-ray photoelectron spectroscopy (XPS). Electrical properties of synthesized ceramic samples were studied by means of impedance spectroscopy.

Cu 7 GeS 5 I superionic ceramics were prepared from nanocrystalline powder, obtained by ball milling. From the structural investigations the average grain size of nanocrystalline powder was determined. Electrical conductivity measurements were carried out in the temperature interval 300–400 K. The temperature dependence of electrical conductivity was analyzed. Cu 7 Gex 5 I-based thin film was obtained by the high target utilisation sputtering. The structural properties were investigated by X-ray diffraction and scanning electron microscopy studies. Optical parameters were obtained using technique of ellipsometry and absorption spectroscopy.

International audience; Nano- and micro-sized La2Mo2O9 ceramics have been successfully synthesized by an aqueous sol–gel synthesis method using a tartaric acid as a ligand. Thermal analysis of both as-prepared La–Mo–O tartrate gel precursor and La2Mo2O9 double oxide heat-treated at different temperatures was performed. The high-temperature phase transition from α to β-phases was additionally investigated by broadband high-temperature impedance spectroscopy techniques. The α ↔ β phase transition was characterized by monitoring the conductivity and a transfer of heat with respect to temperature. The crystalline phase stability of monoclinic La2Mo2O9 compound was confirmed by x-ray diffraction measurements, while the dense nanoscale surface composed of the particles, ranging from 50 to 100 μm, was confirmed by scanning electron microscopy.

Yttria-stabilized zirconia (YSZ) has been studied as a promising material for application as an electrolyte in solid oxide fuel cells. In this work, YSZ powders ((xY2O3 − (1 − x)ZrO2), x = 5, 8 and 10 mol%) were synthesized by three different methods: co-precipitation, sol–gel combustion and sol–gel. The precursor solution obtained by sol–gel method was successfully applied for chemical solution deposition of YSZ thin films on Si(100)/SiO2 substrates. The thermal behavior of Y–Zr–O precursor gels and precipitated Y–Zr oxalates were investigated by TG-DSC measurements. X-ray diffraction analysis was utilized for the characterization of phase purity and crystallinity. Scanning electron microscopy was employed for the estimation of surface morphology features. The quality of obtained ceramic samples strongly depends on the morphology of initial powders. Electrical properties of synthesized ceramics were studied by means of impedance spectroscopy. The highest ionic conductivity was observed for samples prepared by sol–gel combustion synthesis route.

The Li4xTi1-xP2O7 (x = 0, 0.06, 0.1, 0.2) powders have been synthesized by the solid state reaction and their ceramics have been sintered. The Li4xTi1-xP2O7 (x = 0.06, 0.1, 0.2) compounds have cubic superstructure 3×3×3 (space group Pa-3), which is also typical for TiP2O7 pyrophosphate. The electrical properties of the ceramics were investigated in the frequency range of 10 to 3·109 Hz and temperature interval of 400–720 K by impedance spectroscopy. The relaxation dispersion region in the conductivity and dielectric permittivitty spectra of Li4xTi1-xP2O7 (x = 0, 0.06, 0.1, 0.2) ceramics was found.

The synthesis procedure of the Li3Fe2(PO4)3+ Fe2O3 composite is presented. The monoclinic (A type) and hematite phases were detected by X-ray diffraction after the synthesis of the composite. The structural α-β (at a tempera- ture of 460 K) and β-γ (at a temperature of 523 K) phase transitions in the composite were indicated by the anomalies of the electrical conductivity, dielectric permittivity, and changes of activation energies of conductivity. Two phase transitions have been detected in the Li3Fe2(PO4)3+Fe2O3 composite by 57 Fe Mossbauer spectroscopy: the phase transi- tion in Li3Fe2(PO4)3 from the paramagnetic to antiferromag- netic phase at temperature TN=29.5 K and the Morin phase transition in Fe2O3 at temperature TM=235 K.

Structural features responsible for outstanding Li conductivity of Li1 + xRxTi2 − x(PO4)3 (LRTP) Nasicon samples (0 ≤ x ≤ 0.6 and R = Al, Sc, In) prepared by the ceramic route have been analyzed by XRD, ND, MAS-NMR and impedance spectroscopy. The structural analysis showed that all samples display the rhombohedral (S.G. R-3c) symmetry. The structural site occupancy has been investigated by 7Li, 27Al/45Sc and 31P MAS-NMR spectroscopy. The Fourier map differences deduced from high-resolution ND patterns of LAlTP samples revealed that Li ions occupy Li1 sites and to a lower extent Li3/Li3′ sites inside Li2 cavities. The location of Li at 3 sites minimizes electrostatic Li (Li1–Li3) repulsions, enhancing local mobility in LRTP samples. A maximum of conductivity was detected for 0.2 ≤ x ≤ 0.4, when a significant amount of vacant Li1 sites was created at the intersection of conduction pathways. The increment of vacant Li1 sites explains the existence of two Li motion regimes detected by 7Li NMR and impedance spectroscopy. In the low temperature regime, activation energy and migration entropy of Li have been related by the Meyer–Neldel relationship. In the high-temperature regime, further investigation is required to assess the role of vacancy in lithium conductivity., The authors thank MINECO (project MAT2010-19837-C06-02) and the regional Government of Madrid (project S-2009/PPQ 1626) for financial support. The NANOLICOM project (FP7-PEOPLE-2009-IRSES) is also acknowledged. K. Arbi wishes to thank CSIC for the contract JAE-DOC 2009.

Bi 2 WO 6 , Bi 2 MoO 6 , and ZnWO 4 compounds have been synthesized by the microwave method. Their structures have been confirmed by XRD and DTA has been performed on the obtained powders. Dilatometry has been used to optimize the sintering conditions of the Bi 2 WO 6 , Bi 2 MoO 6 , and ZnWO 4 ceramics. The electrical properties of these ceramics have been investigated by the impedance spectroscopy and Hebb–Wagner technique.

Electrical properties of 10 mol% Gd2O3–90 mol% CeO2 (GDC10) and 20 mol% Gd2O3–80 mol% CeO2 (GDC20) ceramics, sintered in various temperatures from 1100 to 1500 °C for 2 h, have been investigated by 2- and 4-electrode impedance measurement methods. The sintering temperature was found to have a significant effect on electrical properties of the grain boundary medium. A brick-layer model-based analysis of the experimental data of grain boundary medium was carried out for the estimation of proportion ratio between grain dimension and grain boundary thickness. Impedance spectra, obtained by 4-electrode method, were also examined by numerically calculating the probability density function of distribution of relaxation times of charge carriers. The latter method revealed time domain behavior of the system, which allowed more accurate evaluation of the most probable relaxation times. GDC10 samples, sintered at 1400 and 1500 °C, showed a particular relaxation behavior of charge carriers in grain boundary medium. Two distinct peaks of the imaginary impedance (both associated to grain boundary) were detected, which suggest that grain boundary medium in these specimens may consist of two phases with different electrical properties.

Cu7PS6 crystals were grown using direct crystallisation from the melt (Bridgman–Stockbarger technique). The crystal structure of Cu7PS6 was determined by X-ray powder diffraction. Cu7PS6 crystallise in the cubic structure, space group P213 (No. 198), the lattice parameter a = 9.6706(1) Å, formula units per cell Z = 4. Electrical properties of Cu7PS6 crystals were studied in the frequency range 10–1010 Hz and in the temperature interval 296–351 K. The performed analysis shows that the Cu7PS6 crystals are mixed electron-ionic conductors with some growth defects.

The Na2Zn0.5Mn0.5P2O7 powder was prepared by the solid state reaction method. The powder structure was studied by X-ray diffraction (XRD) in the temperature range from room temperature (RT) to 520 K. The results of XRD measurements show that the obtained Na2Zn0.5Mn0.5P2O7 is a mixture of two phases: Na2MnP2O7, which crystallizes in the triclinic space group P1, and Na2ZnP2O7, which crystallizes in the tetragonal space group P42/mmm. The chemical compositions of the powder and ceramic samples were investigated by an energy dispersive X-ray spectrometer (EDX) and X-ray fluorescence spectroscopy (XFS). The surface of ceramics was examined by X-ray photoelectron spectroscopy (XPS). The electrical conductivity and dielectric permittivity of the ceramics were investigated from RT to 700 K in the frequency range 10–109 Hz. The relaxational dispersion of electrical conductivity in the investigated frequency and temperature range was found.

Cu6PS5I superionic ceramics were prepared from nanocrystalline powder, obtained by ball milling. From the structural investigations the average grain sizes of nanocrystalline powders were determined. Electrical conductivity measurements were carried out in the temperature interval 300–400 K and in the range of frequencies 10 Hz–3 GHz. The temperature and frequency dependences of electrical conductivity were analyzed. The influence of grain size effect on the electrical conductivity in Cu6PS5I superionic ceramics was studied.

The electrical properties (impedance and electric conductivity) of various VO•• conductors have been investigated in broad frequency (from 10 Hz to 3 GHz) range and wide temperature (from ambient to 1000 K) interval by impedance spectroscopy methods. Two different impedance spectroscopy techniques were used for measurements of electrical properties. Investigations in low frequency range (from 10 Hz to 2 MHz) were performed by 2-electrode method. Corresponding investigations in the high frequency range (from 0.3 MHz to 3 GHz) were based on coaxial waveguide technique. Results allowed us to consistently explore peculiarities of dispersion of electrical properties attributed to charge carrier relaxation. Lightly depressed semicircular shape of relative impedance arcs was observed in complex plane plots, which was assumed as a consequence of existence of a distribution of relaxation times. This phenomenon was studied in more detail examining experimental data and numerically solving integral equation (Fredholm integral equation of first kind) for obtaining the distribution of relaxation times (DRT) function. Analysis of measured data revealed minor DRT function narrowing with temperature increase for all the investigated compounds.

LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7 were synthesised by solid-state reaction and ceramics were sintered. The structure of compounds was studied in the temperature range 300–700 K by X-ray diffraction. Ceramics’ surfaces were investigated by scanning electron microscope. Binding energies of Fe 2p, P 2p and O 1s core levels at ceramics’ surfaces have been determined by X-ray photoelectron spectroscopy and different valence states of Fe and P were detected. Elemental compositions of the compounds were studied by energy dispersive X-ray spectrometer. Impedance spectroscopy was performed in the frequency range 10 Hz–3 GHz and in the temperature interval 400–700 K. The changes of the activation energy of ionic conductivity at 528 and 550 K for LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7, respectively, were found. The phenomena can be related to disordering in the unit cells of the compounds.

New Cu + conducting superionic composites based on Cu 6 P 1 − x As x S 5 I solid solutions were fabricated by mixing microcrystalline powder with polyvinyl acetate glue. The comparative analysis of electrical properties in Cu 6 AsS 5 I single crystal and composite is performed. Frequency and temperature behaviour of electrical conductivity in Cu 6 P 1 − x As x S 5 I composites, measured in the frequency range 10 Hz–3 GHz at 300–400 K are studied. Composition dependences of electrical conductivity and activation energy are analysed. The effect of P → As cation substitution on electrical conductivity and activation energy in Cu 6 P 1 − x As x S 5 I composites is investigated.

The principle of spark plasma ceramics sintering method is presented, its advantages and disadvantages are discussed. Li+ ionic conductor Li3xLa2/3–xTiO3 (x = 0.1) and oxygen ionic conductor CeO2-20 mol% Sm2O3 nanoceramics have been prepared using this method. Electrical properties of the obtained ceramics were measured in the broad frequency range of 10 Hz to 3 GHz and temperature interval from 300 K up to 800 K. Ionic conductivities inside grains and in the grain boundaries have been separated from impedance spectra.DOI: http://dx.doi.org/10.5755/j01.ms.19.3.2403

Nanocrystalline Cu6PS5I powder has been mixed with As2S3 semiconducting glass to obtain nanocomposite. Surface of the obtained sample has been photographed by scanning electron microscope. Electrical properties of Cu6PS5I–As2S3 nanocomposite have been measured using two- and four-probe methods. The obtained results were analyzed by fitting the experimental data to the equivalent circuit model. Warburg impedance element described Cu6PS5I nanoparticles, and the phase transition of this material was indicated.

An impedance and electric conductivity of 10 mol%Y 2 O 3 –90 mol%ZrO 2 and 15 mol%CaO–85 mol%ZrO 2 single crystals were investigated in frequency range from 10 Hz to 3 GHz at temperatures from room temperature to 970 K by impedance spectroscopy methods. Investigations in the high frequency range were performed by the measurement of S -parameter matrix for a 2-port network of a coaxial waveguide and a sample, inserted in the gap of a central conductor. At the low frequencies 2- and 4-electrode methods were used for accurate measurements of the impedance and electrical conductivity. The quality of the experimental data was verified using Kramers–Kronig transforms. The obtained frequency dispersion of the electrical properties related to charge carrier relaxation in the electrical field was examined in terms of distribution of relaxation times (DRT). DRT function was obtained by numerically solving the Fredholm integral equation of first kind with newly developed Matlab application. Analysis of the experimental data has revealed slight spreading of the relaxation time distribution with temperature decrease for both single crystals. The temperature dependencies of the relaxation time corresponding to the DRT function peak showed Arrhenius behavior with activation energy close to that of electrical conductivity.

International audience; In compound Li1.3Al0.3Ti1.7(PO4)3, the investigation by solid state NMR of the T1 and T2 relaxation times of 27Al and 31P nuclei are used to study, versus temperature, the local dynamic properties at different lattice points. Our results can be summarized in the following way: (i) Inside the NASICON framework, these two nuclei do not undergo any diffusion motion. (ii) The motion of the skeleton M(IV)(PO4)3 induces fluctuations in the P–O and Al–O bonds, giving rise to quadrupolar fluctuations for 27Al and chemical shift fluctuations for 31P. (iii) The static distortions induced by these motions allow an explanation of some structural aspects.

International audience; Because of its high Li+ conductivity, the family Li1+xAlxTi2–x(PO4)3 has already been widely studied; previous structural characterizations reported that aluminum occupied two types of sites in the NASICON framework: the first one in octahedral coordination corresponding to Ti/Al substitution; the second one in tetrahedral coordination corresponding to P/Al substitution. In this work we show that it is possible to synthesize samples presenting only the Ti/Al substitution in the octahedral site, which is more consistent with the formulation. The static local properties of our samples were characterized by multinuclear nuclear magnetic resonance (NMR) and X-ray diffraction. The MAS NMR aluminum spectrum is characterized by a strong parameter of asymmetry (ηQ = 0.9), indicating that aluminum ions are situated in sites which lost their axial symmetry. This loss of symmetry is accompanied by an increase of the number of chemical sites of the phosphorus, among which some are characterized by broad lines. The strong asymmetry quadrupolar parameter, together with the strong broadening of the 31P lines assigned to phosphorus with three Ti4+ and one Al3+ are marks of the M2(IV)PO4 skeleton’s distortion. The multinuclear NMR experiment also allowed us to analyze the abnormal behavior of the lithium quadrupolar parameter νQ in relation with the flexibility of the M2(IV)PO4 skeleton characteristic of the NASICON family.

Li 1.3 Al y Y x − y Ti 1.7 (PO 4 ) 3 (x = 0.3; y = 0.1, 0.2) solid electrolyte compounds were synthesized by solid state reaction and studied by X-ray diffraction. At room temperature the compounds belong to a rhombohedral symmetry (space group R 3 ¯ c) with six formula units in the unit cell. Ti 2p, O 1s, P 2p, Li 1s, Y 3d, and Al 2p core level XP spectra at Li 1.3 Al y Y x − y Ti 1.7 (PO 4 ) 3 (x = 0.3; y = 0.1, 0.2) ceramic surfaces have been determined by XPS. The measurements of the electrical properties of the ceramic samples in the frequency range 10 Hz–1 MHz were carried out by a two probe method and a four probe method. The measurements in the microwave range (3 · 10 5 –3 · 10 9 ) Hz were performed in a coaxial line, the part of the inner conductor which was replaced by the sample. The investigation of the electrical properties of the ceramic samples was carried out in air in the temperature range (300 to 700) K. The increase of the stoichiometric factor y of the compounds leads to the increase in the total and bulk conductivities of ceramics and decreases their activation energies.

Li1.3Al0.3 − xScxTi1.7(PO4)3 (where x = 0, 0.1, 0.15, 0.2, 0.3) lithium ionic conductors were prepared by Pechini process. Single NASICON-type phase was detected by X-ray powder diffraction analysis for all synthesized compounds. Ceramic samples have been sintered and investigated by impedance spectroscopy in broad frequency and temperature ranges. The dispersions of electrical parameters correspond to lithium ion migration in the bulk and possibly two different grain boundaries of the ceramics.

Electrical and dielectrical properties of Cu 6 PS 5 I 1 − x Cl x superionic composites, obtained by mixing of microcrystalline powder with polyvinylacetate, are studied. Compositional dependences of their electrical conductivity and dielectric permittivity, measured in the frequency range of 10 Hz–3 GHz at 300–400 K, are analyzed. The effect of compositional disordering on electrical and dielectrical properties at I → Cl anionic substitution in the Cu 6 PS 5 I 1 − x Cl x superionic composites is investigated.

article i nfo Li3xLa2/3 −xTiO3 (where x=0.08, 0.1, and 0.12) lithium ionic conductors were investigated by impedance spectroscopy in broad frequency and temperature ranges. Three relaxation processes, corresponding to lithium ion migration in the bulk and grain boundaries of the ceramics and electrode polarization, were observed in the impedance spectra. Temperature dependences of the bulk ionic conductivity of all the investigated ceramics show non-Arrhenius behaviour. The experimental data have also been analyzed by using the dielectric spectra and applying Cole-Cole function for data fitting. Several relaxations of Li + ions in the bulk of LLTO ceramics have been found.

Li + ionic conductors are able to undergo topotactic exchange reaction in acidic medium. This reaction is illustrated, at room temperature, in the case of lithium lanthanum titanate powder (Li 3x La 2/3 − x □ 1/3 − 2x )TiO 3 (named LLTO). Thermogravimetric analysis, infrared spectroscopy, 7 Li NMR and 1 H NMR clearly showed that such an exchange reaction also occurs on the microstructured powder of LLTO at room temperature after several months in ambient atmosphere (relative humidity: 50%). The reaction with water and CO 2 contained in air leads to the formation of partially protonated titanates and lithium carbonates at the surface of the grains. A mechanism of reaction is proposed: the titanate would be able to dissociate water on the grain surface and then exchange H + for Li + into the perovskite structure, and lithium hydroxide is then formed on the grain surface and reacts with CO 2 contained in air to form Li 2 CO 3 . It will also be shown that this mechanism is reversible. This surface reaction is greatly enhanced by the use of nanomaterials and the increase of the specific surface area of the powder. It occurs rapidly after synthesis under ambient atmosphere. Therefore great care has to be taken in the storage of powders made of nanograins to avoid any chemical reaction with the surrounding environment.

The powder of Li1 + xAlyScx − yTi2 − x(PO4)3 with x = 0.3 and y = 0.1, 0.15, 0.2 has been prepared by solid state reaction and the ceramics have been sintered. The results of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy up to 109 Hz are presented. At room temperature the compounds belong to the rhombohedral symmetry (space group R3c). Ti 2p, P 2p, O 1s, Sc 2p, Al 2p, and Li 1s core level XP spectra's were fitted. The values of binding energies of core level XP spectra's, splitting energies of Ti 2p3/2–Ti 2p1/2, Sc 2p3/2–Sc 2p1/2, P2p3/2–P2p1/2 spin-orbit doublets, and amount of the elements with different binding energies were found to be dependent on stoichiometric factor y. The elemental compositions are defined by EDX. Impedance spectroscopy study in the frequency range 10 Hz–3 GHz have shown three relaxation dispersion regions of electrical properties and the processes are thermally activated. The high frequency dispersion region may be attributed to the relaxation processes in bulk, while lower dispersion regions are related to the processes in grain boundaries and blocking Pt electrodes.

An experimental method and a corresponding setup have been developed for investigation of impedance spectra and other electrical properties of solid materials in radio frequencies from 300 kHz to 3000 MHz and temperature range 300–1200 K. The method is based on the measurement of S-parameters for a 2-port network made of a coaxial waveguide and a sample, inserted in the gap of a central conductor. Experimental setup is based on measuring device — Agilent E5062A network analyzer and is controlled by an application developed on base of Matlab environment. A sample holding coaxial waveguide is made of platinum covered refractory ceramics, which distinguishes itself by low thermal expansion; this enables accurate impedance measurement at high temperatures.

The powder of 10GDC, 15SDC, and 8YSZ compounds with different surface areas (SBET) was used for the sintering of the ceramics. The sintering of the ceramic samples was conducted in air at 1773 K. The surfaces of the ceramics were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The complex impedance and electric conductivity in frequency range (10–3⋅109) Hz and temperature range from 300 to 700 K were carried out. Relaxation dispersions of the electrical parameters were found for all compounds. The dispersions are caused by the oxygen vacancy (VO••)transport in grain boundaries and bulk of the ceramic samples. The values of the bulk and total conductivities of the samples depend on the SBET of the powder used for sintering of the ceramics.

At room temperature solid electrolyte Li3−xSc2−xZrx(PO4)3 (x = 0, 0.1) compounds belong to monoclinic symmetry (space group P21/n) and the compound with x = 0.2 belongs to orthorhombic symmetry (Pbcn). At 900 K all the investigated compounds belong to orthorhombic symmetry (space group Pbcn). Anomalies of enthalpy, change of activation energy of ionic conductivity, anomalies of dielectric permittivity in the temperature range 420 K–660 K of investigated compounds with x = 0 and 0.1 were found. The phenomena are related to structure phase transition in the compounds. The relaxation dispersion regions were found in conductivity spectra for the all investigated samples. The frequency dispersion regions are caused by the relaxation processes in grain, grain – boundaries and electrodes. The temperature dependencies of the bulk conductivity and relaxation frequency in the bulk are governed by the same activation energy. It is shown that major role in the temperature dependence of bulk conductivity is played by ...

X-ray diffraction studies of Cu 6 AsS 5 I crystals grown using the chemical vapor transport method are performed. Complex electrical conductivity, impedance, dielectric permittivity, and electrical modulus of Cu 6 AsS 5 I crystal are studied in wide frequency range and temperature interval from 100 to 400 K. Different contributions into electrical conductivity spectra are revealed. Two phase transitions are confirmed for Cu 6 AsS 5 I from the frequency and temperature dependencies of electrical properties.

The solid electrolyte Li2.9Sc1.9− y Y y Zr0.1(PO4)3 (where y = 0, 0.1) compounds belong to monoclinic symmetry (space group P21/n) at room temperature. The Zr 3d, Sc 2p, P 2p, Y 3d, O 1s, and Li 1s core level X-ray photoelectron spectra (XPS) were fitted. The Li ions in ceramics without Y occupy two different positions and in the ceramics with Y they occupy one position in the lattice. The deconvolutions of the Zr 3d, P 2p, Sc 2p, and Y 3d core level XPS are associated with different valence states on the surfaces of the investigated ceramics. Anomalies of enthalpy, change of activation energy of ionic conductivity, anomalies of dielectric permittivity in the temperature range 420–520 K of investigated compounds were found. The phenomena are related to diffuse structure phase transition in the compounds. At temperatures 600 and 900 K, the compounds belong to orthorhombic symmetry (space group Pbcn).