Analysis Of Impedance Spectra Research Articles

Analysis of Resonance Mechanism of AC Submarine Cable Delivery System for Offshore Wind Power

Abstract Several resonant overvoltage accidents caused by machine-grid interaction in offshore wind power generation systems have led to significant economic losses over the years. To solve this problem, based on the equivalent distributed parameter circuit model of AC submarine cable delivery system, a method combining impedance simulation-time domain simulation and spectrum analysis is proposed to reveal the mechanism of resonant overvoltage and its influencing factors. First of all, considering the phase locked loop (PLL) model and the cable distribution parameter model, an impedance model of AC submarine cable delivery system for offshore wind power is established, which takes into account the dynamic characteristics of PLL and current loop, and provides a model basis for the theoretical analysis. Then, equations for current and frequency at the point of common coupling (PCC) are derived to analyze the mechanism of resonant overvoltage generation and the influence of submarine cable length and power grid strength on resonance. Finally, PSCAD is used to verify the resonance mechanism of AC submarine cable delivery system and its influencing factors.

Electrochemical behaviour of redox-robust electrode in contact with protonic electrolyte: Case of double-layered Sr2Fe1.5Mo0.5O6-δ - Ce0.8Sm0.2O2-δ composite

Electrochemical devices based on proton-conducting oxides offer a significant potential for implementation in a variety of high-temperature electrochemical applications. It is a well-known fact that electrochemical devices require active electrodes to function optimally. Over the last few years, Sr2Fe1.5Mo0.5O6-δ has received much attention as an effective redox-robust electrode for oxygen conducting electrolytes. This study presents, for the first time, the results of investigations on a double-layered composite electrode based on Sr2Fe1.5Mo0.5O6-δ in contact with a barium-free proton-conducting electrolyte La0.9Sr0.1ScO3-δ. It was found that the investigated electrode exhibits low polarization resistance about 0.15 and 0.22 Ohm cm2 in wet air and wet hydrogen at 600 °C, respectively. In addition, the electrode exhibits acceptable redox stability and CO2 tolerance. Also, the results of electrochemical impedance spectra analysis and a discussion on the parallel pathways of hydrogen oxidation and oxygen reduction reactions and the nature of rate-determining steps are presented in the manuscript. The obtained results show the high prospects for a Sr2Fe1.5Mo0.5O6-δ - based composite electrode for protonic ceramic electrochemical cells.

Electrical analysis and molecular dynamics of anion in ferroelastic [(CH3)4P]2CoBr4 crystal near high-temperature phase transitions

The recent technological advances require an aligned innovation in the materials used for the construction of electronic devices. Hybrid materials play a important role in the optoelectronic applications because they combine both the organic and inorganic components. To this end, the [(CH3)4P]2CoBr4 compound was successfully synthesized using the slow evaporation solution growth approach at room temperature. In-depth research has been conducted on the structural, morphological, vibrationnal and electrical characteristics. The [(CH3)4P]2CoBr4 compound crystallises in the monclinic system with P121/C1 space group. The examination of SEM images reveals that the majority of grains have an average size of around 4 μm with irregularly shaped and non-spherical particles. The measured Raman spectra demonstrate the coexistence of two transition phases located at 373 K and 428 K. In fact, these observations suggest that the anionic components play a significant role in influencing the phase transitions mechanism. Analysis of the complex impedance spectra reveals that the electrical characteristics of the material is strongly dependent on both frequency and temperature. That indicates the existence of a relaxation phenomenon and of a semiconductor-type behavior. One single semicircle is detectable in the Nyquist plots of the complex impedance spectra, which can be satisfactorily fitted with a combination of R//C//CPE elements assigned to the bulk response. Therefore, we can conclude from this behavior that the sample is electrically homogeneous. The dependency of s(T) on temperature also shows that the correlated barrier hopping and the non-overlapping small polar on tunneling model are the responsible mechanisms for the AC conduction in [(CH3)4P]2CoBr4.

The aging pattern of lithium-ion batteries based on experiments at different temperatures

Abstract In this paper, we take an 18650-type LiFePO4 battery as the research object to investigate the aging mechanism of Li-ion batteries at different temperatures. The aging tests are conducted at 25°C, 35°C and 45°C. The results show that elevating the operating temperature can improve the cycle life of Li-ion batteries. The aging mechanism was analyzed by incremental capacity and electrochemical impedance spectrum analysis. The following conclusions were obtained: the aging mechanism of lithium-ion batteries mainly includes loss of lithium inventory, loss of active material, and conductivity loss, among which loss of lithium inventory and loss of active material are the main causes of Li-ion battery aging, and the contribution of conductivity loss is the smallest. Further analysis of the causes of battery aging by disassembling and testing the aging electrode sheet SEM and TEM shows that the aging of Li-ion battery is manifested by the rupture of graphite particles, the generation of SEI layer and lithium dendrite, and increasing the temperature can ease the rupture of graphite particles and the generation of lithium dendrite, thus improving the cycle life of the battery.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8

We report the experimental determination of the magnetic exchange parameter ( J/kB = 2.88 ± 0.02 K) for the Spin-3/2 ferromagnetic (FM) Kagomé lattice system: Co3V2O8 using the temperature dependence of dc-magnetic susceptibility χ(T) data by employing the fundamental Heisenberg linear chain model. Our results are quite consistent with the theoretically reported nearest neighbor dominant FM exchange coupling strength Jex−NN∼ 2.45 K. Five different magnetic phase transitions (6.2–11.2 K) and spin-flip transitions (9.6–7.7 kOe) have been probed using the ∂ ( χT )/ ∂T vs. T, heat capacity (CP -T) and differential isothermal magnetization curves. Among such sequence of transitions, the prominent ones being incommensurate antiferromagnetic (AFM) state at 11.2 K, commensurate AFM state at 8.8 K, and commensurate FM state across 6.2 K. All the successive magnetic phase transitions have been mapped onto a single H-T plane through which one can easily distinguish the above-mentioned different phases. The magnetic contribution of the CP -T near TN (11.2 K) has been analyzed using the power-law expression CM = A|T — TN|−α resulting in the critical exponent α = 0.18 ± 0.01 (0.15 ± 0.003) for T < TN (T > TN ), respectively for the Co3V2O8. It is interesting to note that non-Debye type dipole relaxation is quite prominent in Co3V2O8 and was evident from the Kohlrausch–Williams–Watts analysis of complex modulus and impedance spectra (0 ⩽β⩽ 1). Mott’s variable-range hopping of charge carriers process is evident through the resistivity analysis ( ρac -T −1/4 ) in the temperature range 275 ∘C–350 ∘C. Moreover, the frequency-dependent analysis of σac (ω) follows Jonscher’s power law yielding two distinct activation energies ( Ea∼ 0.37 and 2.29 eV) between the temperature range 39 ∘C–99 ∘C and 240 ∘C–321 ∘C.

Effects of Fe2+ on dielectric and magnetic properties in rare earth garnet type high entropy oxides

Given the important role played by the valence state of the transition metal in determining material this paper investigates the effect of Fe2+ content on the structure and dielectric properties of garnet-structured high entropy oxides (Y0.2Eu0.2Er0.2Dy0.2Lu0.2)3(Al0·5Fe0.5)5O12 through Fe2+ doping. The results of XPS and Mӧssbauer spectra showed that the Fe2+ content in the tetrahedron increased with Fe2+ doping. With increasing Fe2+ content, the dielectric constants gradually increased, and the maximum dielectric constant reached 2.78 × 104 at 100 Hz under 30 °C. The analysis of the AC impedance spectrum and electrical conductivity revealed that the difference between the activation energy of grain boundary and grain conductivity resulted in increased dielectric constants of the samples. In addition, the doping of Fe2+ increased the maximum magnetization of the samples. This work provides a new idea for designing giant dielectric materials and magnetic materials with a high entropy strategy.

Disk flower-like structure of PANI Modulated electronic transport dynamics of Sr[formula omitted] ferrite

This study conducted a comprehensive analysis of the low frequency-based electrical characteristics of ferrite composites, exploring the influence of morphology on tunning and optimizing dielectric and conductivity relaxation. Specifically, composites of PANI: Sr CoxZnxFe12−2xO19 in 1:4 ratio by weight, with varying levels of substitution x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 were synthesized using the physical blending method. X-ray diffraction analysis of composites shows the existence of M-type hexagonal and PANI particles, along with some secondary phases in all synthesized samples. The morphology of composites revealed disk flower-like and hexagonal platelet-type structures of PANI and hexagonal ferrite, respectively. Substituting Co–Zn ions induced a non-linear increase in grain size from 0.781 to 1.566 μm, calculated using ImageJ software. The dielectric and electrical properties of composites were examined over the frequency range of 20 Hz to 2 MHz. The replacement of Fe ions with Co–Zn ions resulted in a non-linear variation in conductivity and is maximum for FP3 (1.33 × 10−2 Ω−1m−1) at 2 MHz. The complex impedance spectra deviated from an ideal Debye type and were modeled using an equivalent circuit encompassing resistances of grain boundaries and grains, grain capacitance, and a constant phase element. Modulus and impedance spectra analysis illustrated the contribution of both grain and grain boundaries in their respective relaxations. The simulation of impedance parameters in EIS software elucidated a substantial value of Cg = 290 μF for FP1, which aligned with the large-sized grain observed in FESEM micrographs.

MoSe2 in flower spheres provides abundant active sites for TiO2 photocatalytic degradation of RhB

In this paper, a MoSe2/TiO2 composite photocatalyst was constructed by modifying TiO2 with MoSe2 as a group catalyst. The results showed that pure TiO2 and MoSe2 had no degradation activity for RhB, and the composite catalyst of 0.03 g MoSe2 had the best photocatalytic degradation activity for RhB. Through SEM, TEM, UV-VIS absorption spectrum, transient photocurrent curve, photoluminescence spectrum, and electrochemical impedance spectrum analysis, it can be seen that the excellent performance of 0.03 g MoSe2 composite sample is due to its excellent nanostructure, and uniform TiO2 nanosheets are attached to MoSe2 flower spheres. The active site of RhB photocatalytic degradation was increased, the visible light response and photobiological carrier separation were enhanced, and TiO2 had photocatalytic activity under simulated sunlight.

Corrosion of 316L stainless steel produced by laser powder bed fusion and powder metallurgy in pressurized water reactor primary coolant

Corrosion mechanism of 316 L stainless steel produced by laser powder bed fusion-hot isostatic pressing (LPBF-HIP) and powder metallurgy-hot isostatic pressing (PM-HIP) is studied with in-situ electrochemical impedance measurements coupled to detailed oxide film characterization. Quantitative analysis of impedance spectra using the Mixed-Conduction Model and estimation of local kinetic and transport parameters by interpretation of in-depth elemental composition profiles indicated lower corrosion and oxidation rates of LPBF-HIP and PM-HIP materials in comparison to conventional wrought 316 L. This owes to a higher fraction of low-angle grain boundaries, smaller grain size, the presence of nano-sized oxide particles and elevated Cr and Ni contents.

Electrochemical impedance of porous tantalum solids: modeling of frequency response

The paper proposes a new approach to the analysis of electrochemical impedance spectra of porous tantalum bodies, which involves modeling the frequency response via an equivalent circuit that takes into account the pore hierarchy. It was shown that the proposed circuit describes well the experimental data and allows characterization of the porous structure, including the contribution of different types of pores to the total capacitance of the porous body, characteristic relaxation times, and activation frequencies for different type pores. Two types of samples were analyzed: a porous tantalum body obtained by sintering Ta powder and a porous tantalum body covered with a Ta2O5 dielectric layer. Modeling showed a significant redistribution of contributions from pores of different types into the total capacitance after the formation of Ta2O5 due tothe preferential isolation of the smallest pores and/or those difficult to access. The results of modeling of the frequency response of the analyzed samples agree well with the scanning electron microscopy data. The proposed approach has the potential to be advantageous for the technology of tantalum capacitors

Magnetic and dielectric properties of Nd-Sn-Cu co-doped yttrium iron garnet ferrite

Ion doping to regulate the magnetic and dielectric properties of yttrium iron garnet ferrites is highly desirable for microwave devices. This study successfully fabricated Y3-xNdxFe4.8Cu0.1Sn0.1O12 (x = 0, 0.5, 1.0, 1.5) ceramics, controlling their magnetic and dielectric properties via Nd ion doping. The results indicate that the introduction of Nd ions into the YIG lattice, occupying dodecahedral sites and replacing Y3+ ions, leads to an increase in the lattice parameter. The hysteresis loops demonstrate that as the concentration of Nd ion doping increases, the saturation magnetization initially decreases and then increases. Additionally, the complex impedance and dielectric spectrum analysis reveal that the resistivity and dielectric constant of the material increase with the increasing concentration of Nd ion doping. The real part of the dielectric constant reaches its maximum value, 29.5@200 kHz, at x = 1.5. Consequently, Nd doping concentration effectively controls the crystal structure, microstructure, magnetic, and dielectric properties of garnet ferrite, enhancing its magnetic and dielectric properties and potential application in microwave devices.

Enhancing grain boundary contributions to improve the dielectric properties of (In0.5Nb0.5)0.05Ti0.95O2 ceramics by Bi aided sintering

The internal barrier layer capacitance effect substantially contributes to the colossal permittivity in In and Nb co-doped TiO2 (INTO) ceramics. Therefore, enhancing grain boundary density and ceramic compactness can efficaciously reduce their low-frequency dielectric loss. In this investigation, Bi2O3 addition was utilized to aid sintering and refine grains for INTO ceramics. The results reveal that Bi-doped INTO ceramics, in contrast to their undoped counterparts, exhibit a more refined and compact grain structure with a significant increase in the quantity of grain boundaries. Moreover, a noticeable reduction in low-frequency dielectric loss from above 0.1 to below 0.05 and enhanced frequency stability of permittivity from below 10 Hz to approximately 10 kHz were observed, along with a decrease in the sintering temperature to 1300 °C. In comparison to undoped INTO ceramics, Bi doping also enhances the withstand voltage capability by a factor of 1.5–4 for Bi-doped INTO ceramics. However, as the sintering temperature of Bi-doped INTO ceramics increases and the grain size enlarges, their breakdown voltage gradually decreases, but the non-linear coefficient of current-voltage characteristics progressively increases. Analysis of complex impedance spectra confirms that the increased grain boundary density and resistance in Bi-doped INTO ceramics is the primary factor for the enhanced dielectric properties and withstand voltage capability.

CO2/Cr-tolerance and oxygen reduction reaction of novel high-entropy perovskite cathode for intermediate temperature solid oxide fuel cell

The development and exploration of cathode oxides with outstanding electrocatalytic activity are critical processes aimed at achieving a decrease in the operation temperature of solid oxide fuel cells (SOFC). Herein, a novel high-entropy oxide, La0.2Pr0.2Nd0.2Sm0.2Gd0.2BaCoFeO5+δ (HEP), which incorporates five lanthanide species (La, Pr, Nd, Sm, and Gd) in the A-site of perovskite, has been specifically developed and assessed as selected cathode for intermediate-temperature SOFC. Investigations of phase structure, chemical compatibility, oxygen transport characteristics, oxygen reaction kinetic, thermal expansion, surface chemical state, conductivity, as well as CO2/Cr-durability are thoroughly performed to assess the basic physicochemical properties of the HEP cathodes. The HEP cathode possesses good operational stability, moderate thermal expansion behavior, fast oxygen transport dynamics, and superior chemical compatibility with the electrolyte. At 700 °C, the polarization resistance low to 0.072 Ω cm2 and output power density high to 332.2 mW cm−2 were obtained for the symmetrical and electrolyte-supported single cells. Furthermore, a stable current density is obtained for the single cell operating at 600 °C and 0.5 V for 100 h. Analysis of electrochemical impedance spectra (EIS) and distribution of relaxation time (DRT) data at different oxygen partial pressures reveal that the charge-transfer and oxygen ions ionization processes at intermediate frequencies present a significant limiting step in the rate of the oxygen reduction reaction. However, under realistic utilization conditions, cathodes of cells often endure irreversible performance degradation owing to the Cr deposition from interconnects or CO2 poisoning in air. Hence, the behavior of Cr and CO2 poisoning is also systematically investigated in symmetrical cell measurements; the results confirm that the HEP cathode displays good resistance to Cr and CO2 poisoning. Overall, our findings indicate that the HEP material is regarded as a favored ceramic cathode for SOFC.

Crystal structure, Hirshfeld surface analysis, conduction mechanism and electrical modulus study of the new organic-inorganic compound [C8H10NO]2HgBr4.

There has been a lot of interest in the development of a novel hybrid material based on mercury that has fascinating structural properties. In this paper, single crystals of [C8H10NO]2HgBr4 was successfully synthesized by the slow evaporation method at room temperature. In fact, the latter crystallizes in the orthorhombic system (Cmca space group) with cell parameters a = 20.824(2) Å, b = 15.352(1) Å and c = 13.700(1) Å and Z = 8. Its structure is constituted by one [C8H10NO]+ cation and one type of isolated anion [HgBr4]2- tetrabromomercurate(ii). The atomic arrangement presents an alternation of organic and inorganic layers along the a-axis. To maintain the cohesiveness of the structure, these components are joined via π⋯π interactions and hydrogen bonds (N-H⋯Br and N-H⋯O). A general network of hydrogen bonds ensures the interconnection of several entities. Greater knowledge of these interactions has been obtained based on the Hirshfeld surface analysis and 2D fingerprint plots. The analysis of complex impedance spectra shows that the electrical properties of the material are heavily dependent on frequency and temperature. The obtained results were analyzed by fitting the experimental data to an equivalent circuit model. The temperature dependence of conductivity and the relaxation frequency ωmax fulfill the Arrhenius relation and activation energies are estimated. The material follows Jonscher's universal dynamic law or here there is a decrease in the exponent 's' as the temperature increases. This result indicates that the Correlated Barrier Hopping (CBH) model represents the conduction mechanism. Besides, the non-Debye type conductivity relaxation is revealed by the electrical modulus analysis.

Synthesis of a new potassium-substituted lead fluorapatite and its structural characterization.

Prismatic crystals of partially potassium substituted lead fluorapatite Pb5.09Ca3.78K1.13(PO4)6F0.87 were grown through a solid-state reaction. The structural study conducted by single-crystal X-ray diffraction revealed that the compound crystallizes in the hexagonal P63/m space group, with unit cell parameters a = b = 9.7190(5) Å, c = 7.1700(6) Å and V = 587.37(7) Å3(Z = 1), as well as final values amounting to R and wR of 0.0309 and 0.0546, respectively. The structural refinement demonstrated that Pb occupies both the (6h) and (4f) structural sites of hexagonal fluorapatite, K occupies the (6h) site, and Ca is placed on the (4f) site. Powder X-ray diffraction study indicated the absence of additional phases or impurities. Chemical analysis using atomic absorption spectrometry and energy-dispersive X-ray spectroscopy confirmed the expected chemical formula. The electrical conductivity measured over a wide temperature range was found to be governed by the ion mobility mechanism in the tunnel along the c axis (probably attributed to the fluorine ion located there). We, therefore, could infer from the analysis of the complex impedance spectra that the electrical conductivity of our apatite depends essentially on the temperature and frequency, which produces a relaxation phenomenon and semiconductor-like behavior. Moreover, the strong absorption in the UV-Visible region was substantiated through studies of the optical properties of the developed sample. Fluorescence spectra exhibited emissions in the orange regions when excited at 375 nm. The findings of the phenomena resulting from the emission and conduction of the apatite in question suggest its potential for application in various technological fields such as photovoltaic cells, optoelectronics, photonics, LED applications, catalysis and batteries.

Crystal structure, optical characterization, conduction and relaxation mechanisms of a new hybrid compound (C6H9N2)2[Sb2Cl8

Hybrid materials play a crucial role in the construction of flexible electronic devices due to the advantages of both organic and inorganic components. To this end, a new hybrid compound (C6H9N2)2[Sb2Cl8] was successfully fabricated using the slow evaporation solution growth approach at room temperature. In-depth research has been done on the structural, optical, and dielectric characteristics. This compound adopts the triclinic symmetry and crystallizes in the centrosymmetric space group P1̄. The inorganic and organic components respectively form anionic and cationic layers parallel to the ac-plane and alternate along the crystallographic b-axis. The [Sb2Cl8]2- dimeric units are bound to the 2-amino-5-picolinium cations [(C6H9N2)]+ through N-H⋯Cl hydrogen bonds. Optical absorption measurements showed a semiconductor behavior with a band gap of approximately 3.57 eV. In addition, DFT calculations were performed to investigate the absorption spectrum, wavelength, and HOMO-LUMO gap. The analysis of complex impedance spectra shows that the electrical conductivity of the sample is strongly frequency and temperature dependent, indicating a relaxation phenomenon and semiconductor-type behavior. Dielectric data obtained from complex impedance spectroscopy and ac conductivity with the use of the Maxwell-Wagner equivalent circuit model, and the universal power law have been investigated to explore the basic components of the electronic transport and relaxation process in our material.

(Invited) Ruddlesden-Popper Oxides As Bi-Functional Oxygen Electrodes

Incorporating more renewables into our energy mix is a major challenge that confronts our transition to a carbon free economy. Solid oxide electrochemical cells when operated alternately in fuel cell and electrolysis modes, enable the incorporation and integration of far greater amounts of solar and wind energy into our power grid. As islanded systems, they can also function as distributed generation systems thereby decreasing our reliance on the power grid. In this talk, we present a recent survey of results on rSOCs based on rare earth nickelate – rare-earth doped ceria composite oxygen electrodes that exhibit excellent cycling behavior when operated alternately in solid oxide fuel cell (SOFC) and solid oxide electrochemical cell (SOEC) modes of operation. The degradation in such cells is significantly mitigated by mode-switching operation when compared to operating in single mode operation in electrolysis mode. By comparing distributed relaxation times (DRT) analysis of impedance spectra obtained from single-mode (electrolysis) operated cells, and cells operated in switched-modes, we obtain clues into cell degradation mechanisms.

Mitigating Chemo-Mechanical Degradation in Sulfide-Based All-Solid-State Batteries Comprising Sulfur Composite Cathode and Li–Si Alloy Anode

In this study, all-solid-state batteries consisting of an Li2S5–P2S5 (LPS) glass electrolyte, a sulfur/LPS glass/carbon composite cathode, and an Li–Si anode are prepared and tested under high cut-off voltage conditions (0.5–3.7 V) to elucidate the effect of LPS redox activity on the chemo-mechanical stability of LPS-based cells. The cell cycled in the voltage range 0.5–3.7 V exhibits unstable charging behaviors and voltage noise, with substantial LPS oxidative decomposition. X-ray photoelectron spectroscopy and impedance spectra analyses of a three-electrode system reveal that the cathode resistance is remarkably increased by the oxidative decomposition of LPS when the cell is charged to 3.7 V, which induces dendritic lithium growth at the anode side, resulting in a micro-short circuit through the electrolyte. Composite anodes of Li3PS4 glass+Li–Si alloy (Type 1) and Li3N+LiF+Li–Si alloy (Type 2) are also prepared for all-solid-state batteries (ASSBs) with LPS glass electrolyte and sulfur/LPS glass/carbon composite cathode. Using a three-electrode system, the anode and cathode potentials are separated, and their polarization resistances are individually traced. Even under high-cutoff-voltage conditions (3.7 V), Type 1 and 2 cells are stably cycled without voltage noise for >200 cycles. Although cathode polarization resistance drastically increases after 3.7 V charge owing to LPS oxidation, LPS redox behavior is fairly reversible upon discharge–charge unlike the non-composite alloy anode cell. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis reveals that the enhanced cyclability is attributed to uniform Li–Si alloying throughout the composite anode, providing more pathways for lithium ions even when these ions are over-supplied via LPS oxidation. These results imply that LPS-based cells can be reversibly cycled with LPS redox even under high-cutoff voltages, as long as non-uniform alloying (lithium dendrite growth) is prevented.

Exploring the electronic structure of BiVO4 thin films using energy-resolved electrochemical impedance spectroscopy

Bismuth vanadate (BiVO4) is a promising photoelectrochemical water-splitting semiconductor. This study focuses on elucidating the electronic structure of BiVO4 by analyzing energy-resolved electrochemical impedance spectroscopy (ER-EIS) data. The primary objective is to demonstrate the effectiveness of the ER-EIS, which is typically applied to organic semiconductors, in estimating the band edge positions of BiVO4 films deposited on FTO substrates.The impedance spectra analysis as a function of an applied overpotential permits an estimation of the density of states, where the limits correspond to the valence (VB) and conduction band (CB) edge positions that determine the redox reactions the semiconductor can promote. The energy difference between the CB and VB corresponds to the material's band gap (Eg). The calculated Eg using ER-EIS closely matches the reported optical properties of the material, and the energy positions of the VB and CB align with the reported values for BiVO4.

Microstructure and electrical conductivity of La10Si6O27–La0.9Sr0.1Ga0.8Mg0.2O2.85 composite electrolytes for SOFCs

Composite ceramic electrolytes with heterostructure have attracted wide attention from the scientific community due to their enhanced conductivity and stability compared with single component electrolytes. Along these lines, in this work, to improve the conductivity of lanthanum silicate, a series of La10Si6O27 (LSO) - La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolytes were developed, which were composed of apatite/perovskite heterostructure. The phase composition, heterogeneous structure, and morphology of the samples were investigated by performing X-ray diffraction (XRD), transmission electron microscopy (TEM) measurements, as well as, field emission scanning electron microscopy (FE-SEM) for in-depth analysis. In addition, the Archimedes method was employed to test the relative density of the samples. X-ray photoelectron spectroscopy (XPS) was used to examine changes in oxygen vacancies at different LSGM contents. Compared with the pure LSO material, the content of oxygen vacancies increases significantly and the conductivity is highest when the LSGM content is 10 %, which indicates that the newly formed oxygen vacancies in the composite LSO-LSGM electrolyte play an important role in improving the ionic conductivity. At 400 °C, the conductivity of 90 wt%LSO:10 wt%LSGM was 3.4 times that of pure LSO, and at 600 °C, the conductivity of 90 wt%LSO:10 wt%LSGM was an order of magnitude higher than that of pure LSO. From the electrochemical impedance spectra (EIS) analysis, it was shown that the small resistance achieved by the grain boundary was the main reason for its excellent performance. Our results provide valuable insights for the design of more composite electrolytes for intermediate-temperature SOFCs.