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GDC (Gd-doped CeO 2) play a dual role in solid oxide fuel cell (SOFC), effectively blocking the reaction between YSZ (Y 2 O 3 -doped ZrO 2) electrolyte and high-performance cathode materials such as La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ , and improving the low-temperature oxygen ion transport in composite cathodes. It is crucial to systematically investigate the influencing mechanism of Gd-doping on conductance and thermal matching of CeO 2 for high-efficiency and stable SOFC. In this paper, the physical phase, morphology and electrochemical performance of Ce 1-x Gd x O 2- δ (x = 0.1, 0.15, 0.2, 0.25) were characterized, and the thermal matching between GDC and other cell components was investigated by finite-element thermal stress calculations and cold-heat-cycling tests. The results indicate that Ce 0.8 Gd 0.2 O 2- δ obtains the optimum conductivity, whether in the low temperature segment affected by the grain boundary with the space charge layer, or in the activation energy controlled medium temperature segment. Moreover, the finite-element calculation shows that the thermal stresses of the electrolyte facing the barrier layer and the barrier layer facing the cathode decrease gradually with the increase of Gd-doping. Consequently, the cell with Ce 0.8 Gd 0.2 O 2- δ applied to the composite cathode and the barrier layer presents the optimal output performance of 0.87 W cm−2 at 750 °C, and the cell performance decreased by only 1.15 % after 50 thermal cycles between 25 and 800 °C. This is significant for improving the long-term operational stability of SOFC under thermal cycling conditions. [ABSTRACT FROM AUTHOR]

ZrP 2 O 7 is a promising material with excellent thermal and electrical properties. However, when temperature approaches to 563 K, it undergoes a structural phase transition, which will cause large thermal stresses. When Zr is substituted by Y and Nb, a new material of (YNb) 0.2 Zr 0.6 P 2 O 7 , was successfully prepared and the phase transition of material was effectively inhibited. This new material adopts a cubic structure similar to ZrP 2 O 7 , and exhibits medium thermal expansion (α = 7.1 × 10−6 K−1) in the measured range of 200–1073 K. The values of thermal conductivity from RT to 973 K are between 0.4474 W m−1 K−1 and 0.8526 W m−1 K−1, which can be comparable to the values of traditional thermal insulation materials. The dielectric constant and dielectric loss factor at the frequencies above 1 MHz are stable and low. The electrical conductivity of the material indicates that it is electronically insulating at RT-573 K. [ABSTRACT FROM AUTHOR]

Herein, the Zn 2 V 2 O 7 electro-ceramic pyrovanadate was synthesized via a conventional solid-state reaction technique and calcined at 700 °C. The single phase formation of Zn 2 V 2 O 7 pyrovanadate crystallized in the monoclinic structure with C 12/ c 1 space group was confirmed by X-ray diffraction (XRD). The XRD powder diffraction profile was analyzed by Rietveld refinement to investigate the structural details of the compound. The complex impedance analysis was carried out in the frequency domain of 83 − 2 × 10 6 Hz over a temperature range of 453–613 K to study the electrical charge conduction and dielectric relaxation mechanism in the material which revealed the presence of the distribution of relaxation times with thermal charge activation. Depressed semicircles in the Nyquist plots were modeled by an equivalent circuit with configuration (R G C G)(R GB Q GB) which resolved the contributions of grains and grain boundaries towards the transport properties of the material. The electrical conductivity spectra followed Jonscher's power law behavior and the temperature variation of frequency exponent suggested correlated barrier hopping (CBH) as the governing transport mechanism in the Zn 2 V 2 O 7 pyrovanadate system. The comparison between scaling behaviors of imaginary parts of impedance and modulus advocated the temperature-independent nature of relaxation time distribution. The imaginary electrical modulus spectra were reproduced by the Kohlrausch, Williams, and Watt formulism, and the fitted parameters confirmed the non-Debye type nature of the dielectric relaxation. Further, the Haveriliak-Negami function was employed to investigate the dielectric response of the material which was found to be consistent with impedance, conductivity, and modulus analyses. The frequency dispersion of the tangent loss verified that the hopping mechanism was thermally activated. [ABSTRACT FROM AUTHOR]

The use of pore generators is a classical way to adjust the pore size distribution of porous ceramics. However, they must be selected to alter the processing of the ceramic as little as possible. Petroleum coke is an attractive pore generator for some ceramic compositions hard to process with other pore generators as starches. The analysis of the behaviour of the two main varieties, green coke and calcined coke, as pore generators in ceramic electrodes of Sb-doped SnO 2 have shown that they allow the shaping of the electrodes by dry-pressing, but proportions higher than 10 wt% require great care in the process. The design of the sintering cycle is restricted by their thermal behaviour to a heating rate ≤ 2 °C·min−1 in the 150–600 °C interval to avoid defects in the sintered electrodes. Green coke undergoes a sudden expansion around 270 °C that is absent in calcined coke, but calcined coke oxidises at lower rate and its remainder can reduce SnO 2 to Sn at higher temperatures. Calcined coke generates lower porosity in the sintered specimens than green coke at equal proportion in the raw materials mixture and requires higher proportions to obtain a bimodal pore size distribution. In addition, the type of coke has no definite effect on the properties of the sintered ceramic. In this work, the critical property, electrical resistivity of the electrodes, is mainly related to the generated porosity. The described limitations must be considered prior to select any of two cokes as pore generator in ceramics. [ABSTRACT FROM AUTHOR]

The prime goal of this novel work is to investigate the efficacy of spinel zinc ferrite as a thermoelectric material and its performance enhancement for high temperature applications. Zn 1-x Ni x Fe 2 O 4 (0 ≤ x ≤ 0.2) were prepared by sol-gel method and their structural, morphological, and thermoelectric behaviours were examined as functions of composition and temperature. Among the studied compositions, Zn 0.8 Ni 0.2 Fe 2 O 4 exhibits the highest electrical conductivity (σ) of 49.83 S/m, the largest power factor of 6.66 μW/mK2, and the lowest thermal conductivity (κ) of 0.36 W/mK at 947 K, thus extending to an overall enhancement in the thermoelectric figure of merit (zT). Conduction through electron hopping is proven to be the main driving force for the enhancement in electrical and thus thermoelectric properties. Results reveal that thermoelectric properties of ZnFe 2 O 4 can potentially be enhanced by the doping Ni at Zn site and opens up an exciting opportunity for the utilization of this spinel ferrite as a novel thermoelectric material for applications involving elevated temperatures. [Display omitted] • Thermoelectric figure of merit of ZnFe 2 O 4 was considerably enhanced by doping Ni. • Electron hopping is found to be one of the major contributors for the enhancement of electrical conductivity. • The dopant is also effective in reducing the thermal conductivity of ZnFe 2 O 4 at higher temperatures. • The results indicate that the studied material is suitable for high temperature (>700K) thermoelectric applications. [ABSTRACT FROM AUTHOR]

In this study, the objective was to improve the performance of bismuth vanadium oxide Bi 4 V 2 O 11 by synthesizing double substituted compounds using copper ions Cu2+ and tantalum ions Ta5+. Bi 4 V 2-x Cu x/2 Ta x/2 O 11-3x/4 (0.1 ≤ x ≤ 0.5) polycrystalline samples of were prepared via the solid-state route. XRD patterns measured at room temperature revealed the stabilization of the monoclinic α-Bi 4 V 2 O 11 type structure for x = 0.1 and the tetragonal γ or γ' -Bi 4 V 2 O 11 for x > 0.2. This result has been confirmed by thermogravimetric analysis (DTA), FT-IR spectroscopy and Raman scattering measurements. The influence of the composition on the microstructure and grain size of the prepared samples was explored through dilatometric study, density measurements, and scanning electron microscopy (SEM). Thermal Raman spectra evolution was also investigated. The temperature-dependent Raman spectroscopy analysis of the compound α-BiCuTaVOx (x = 0.1) demonstrated variations in the position, intensity, and width of the Raman mode around 850 cm−1, indicating temperature-assisted structural modifications. One defining feature of the tetragonal-dominated phase of the BiMeVOx systems is the increasing merging of the weak band at 930 cm−1 with the dominating band at 850 cm−1. This behavior was also observed for our samples. The V–O bond lengths were calculated using an empirical relation based on the diatomic approximation. Electrochemical impedance spectroscopy (EIS) was used to investigate the changes in electrical conductivity with the substitution rate across the temperature range of 300–720 °C. The sample with x = 0.3 exhibited the highest electrical conductivity at both high and low temperatures. However, the optimal substitution rate to achieve the best conductivity in this series of copper and tantalum-substituted BiCuTaVOx was found to be x = 0.3 (σ = 4 × 10−3 S cm−1 at 600 °C). [ABSTRACT FROM AUTHOR]

In this work, we study the effect of Ni-doping on the structural and impedance spectroscopy properties of the polycrystalline YCrO 3 ceramic sample. The structural analysis shows all the samples crystallize in an orthorhombic structure with the Pnma space group. The depressed and asymmetric semicircle of complex impedance spectra indicates that the relaxation of charge carriers is of non-Debye type, where the thermally activated charge carriers control it. The temperature dependence of relaxation time and electrical conductivity exhibit an anomaly in the vicinity of diffuse-like relaxor transition temperature (T C ∼ 460 K). The analysis of conductivity data shows hopping-type charge conduction. The analysis further indicates that while the dc conductivity increases continuously, the activation energy shows a non-monotonous variation with Ni concentration. [ABSTRACT FROM AUTHOR]

This study aims to optimize the Pr 2 NiO 4+δ electrode material for increased phase stability at IT-SOFC operating temperatures while maintaining high electrochemical activity. This is achieved by double doping at both Pr and Ni sites. The series of new Pr 1.6 Ca 0.4 Ni 1–y Cu y O 4+δ complex oxides are synthesized by the pyrolysis of the glycerol-nitrate compositions. The resulting materials are extensively studied by room and high-temperature XRD, XPS, TGA, SEM, dilatometry, DC-four probe method, and impedance spectroscopy. The study has registered the formation of the homogeneous complex oxide phases with an orthorhombic structure (Bmab sp. gr.) throughout the dopant concentration range of y = 0.0–0.4. For the Cu-rich samples, an increased Pr4+ content and the presence of Ni2+ and Cu+1 are observed, resulting in a gradual decrease of both the electroconductivity and the absolute oxygen content (δ ∼ 0 at y ≥ 0.2). Nevertheless, the Pr 1.6 Ca 0.4 Ni 1–y Cu y O 4+δ series materials exhibit excellent phase stability and chemical and thermomechanical compatibility with CeO 2 - and BaCe(Zr)O 3 -based electrolytes. Moreover, Cu-doping enhances the electrochemical activity of the electrodes. The polarization resistance of the Pr 1.6 Ca 0.4 Ni 0.8 Cu 0.2 O 4+δ electrode, is in the range of 0.19–0.27 Ω cm2 (at 700 °C) depending on the electrolyte substrate and shows a low dependence on the water content, demonstrating the applicability of the electrode in fuel cells and electrolysis cells based on both oxygen-ion and proton-conducting electrolytes. [Display omitted] • New Pr 1.6 Ca 0.4 Ni 1–y Cu y O 4+δ (y ≤ 0.4) oxides are obtained by glycerol-nitrate pyrolysis. • These oxides exhibit increased phase stability and compatibility with electrolytes. • Double doping maintains satisfactory conductivity level. • Moderate Cu doping enhances electrochemical activity of the electrodes. • Pr 1.6 Ca 0.4 Ni 0.8 Cu 0.2 O 4+δ is a promising candidate for use in IT SOCs. [ABSTRACT FROM AUTHOR]

Pr 2 NiO 4+δ -based materials are considered as promising air electrodes for proton ceramic electrochemical cells due to their wide range of attractive properties. In the present work, the basic functional properties of Pr 2 NiO 4+δ are optimized by substituting Pr-cations with isovalent La- and Nd-ions. The synthesized samples are characterized by X-ray diffraction analysis, thermogravimetry in oxidizing and reducing environments, dilatometry, and four-probe conductivity measurements. As a result, the relationships between crystal and defect structures on the one hand and their electrotransport and thermomechanical properties on the other hand are revealed. The PrLaNiO 4+δ , Pr 1.5 La 0.5 NiO 4+δ , and PrLa 0.5 Nd 0.5 NiO 4+δ compositions are stabilized by the large lanthanum cation and do not show the phase transition (from Fmmm to I 4/ mmm space group) typical of the other studied compounds. The conductivity values of the studied materials remain practically unchanged for most of the compositions, but the La-doping reduces the activation energies of hole transfer. Based on the obtained data, two optimal compositions (Pr 1.5 La 0.5 NiO 4+δ and PrLa 0.5 Nd 0.5 NiO 4+δ) can be identified for their further application in electrochemical cells. [Display omitted] • (Pr x La y Nd z)PrNiO 4+δ (x + y + z = 1) are synthesized by citrate-nitrate method. • Doped materials obtained have orthorhombic structure of Pr 2 NiO 4+δ. • Doping with La or Nd results in a decrease of oxygen content of Pr 2 NiO 4+δ. • Nd- and La-doping have the opposite effect on thermal expansion of Pr 2 NiO 4+δ. • Doping with lanthanum reduces the activation energy of hole mobility. [ABSTRACT FROM AUTHOR]

Higher Manganese Silicides (HMS) are the best p-type materials beneficial for intermediate-temperature range thermoelectric device applications due to their high thermal stability and inexpensive constituent elements. Although the cost-effective HMS materials possess high thermal stability, they are concerned with high thermal conductivity values. The nanocomposite approach was promised to lower the thermal transport properties without affecting the electrical transport properties, which is experimented in the present work. The higher manganese silicide with varying weight percentages of nano-structured Si 0.8 Ge 0.2 B 0.02 inclusions was experimented to decrease the thermal conductivity and to enhance the electrical properties. The lowest thermal conductivity value of ≃ 2.24 W/mK was reported with 2 wt% Si 0.8 Ge 0.2 B 0.02 addition in HMS material. Also, the HMS-2 wt. % Si 0.8 Ge 0.2 B 0.02 improved the transport properties, electrical conductivity and Seebeck coefficient values of ≃ 4 × 104 S/m and ≃ 220 μV/K respectively. Furthermore, various mathematical models were proposed here to simulate the composite approach results, which were then correlated with experimental results. [ABSTRACT FROM AUTHOR]

Lanthanum nickel oxide (LaNiO 3, LNO) films exhibit excellent electrical conductivity but poor mechanical properties, considerably limiting their further development in the field of flexible electronics. In this study, flexible LNO thin films of different thicknesses were fabricated on a unique two-dimensional (2D) mica platform using a simple metal organic deposition technique. The obtained LNO films exhibited a pseudocubic phase without impurities. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterisations proved that the films were well-crystallised, dense, and flat, with controllable thickness. In addition, the flexible LNO/mica element possesses low resistivity (5 × 10−4 Ω cm), translucency, and good bending resistance. The electrical resistivity can remain stable under various bending radii (r = 10∼2 mm), thousands of bending cycles, and a wide temperature range (28–200 °C), demonstrating good durability, mechanical stability and temperature resistance. Furthermore, a ferroelectric BiFeO 3 film was constructed based on the obtained conductive LNO electrode, which exhibited typical ferroelectric characteristics. This excellent performance suggests that the flexible LNO electrode is promising for flexible electronic applications. [ABSTRACT FROM AUTHOR]

This study investigated the effect of TiO 2 content on the viscosity, free running temperature, electrical conductivity, crystallization behavior, and structure of high-titanium CaO–SiO 2 -10 wt% MgO-13 wt%Al 2 O 3 –TiO 2 -4 wt.% FeO slag by experiments and molecular dynamics simulations. The results revealed that increasing TiO 2 weakened the overall bonding energy and simplified the slag structure, leading to a decrease in viscosity and an increase in electrical conductivity. Thermodynamic calculations revealed a continuous enrichment of the slag towards the pseudobrookite region with increasing TiO 2 content. The precipitation of pseudobrookite phase during cooling resulted in short-slag characteristics and a rising free running temperature. Additionally, the peak intensity of pseudobrookite phase gradually enhanced and its morphology changed from elongated strips to plates with higher TiO 2 concentration. Structural analysis demonstrated that the poorly stabilized [TiO 6 ] octahedron was the major form of Ti atoms in the slag, and its proportion progressively increased with increasing TiO 2 content. [ABSTRACT FROM AUTHOR]

The synthesis of transparent thermoelectric materials, particularly at low processing temperature possesses a good promise for future power generation by renovating waste heat into electrical energy. The fabrication of invisible thermoelectric module is hindered by limited choices of appropriate p-type transparent thermoelectric materials so far. The present study deals with the growth and characterization of optically transparent p-type copper iodide (γ-CuI) thin films. Thermal annealing (maximum up to 200 °C) was performed to tune the electrical and optoelectronic properties for nurturing the thermoelectric performance. Annealing induced microstructural modifications instigated the preferential crystal growth by regulating the surface morphology. Low thermal conductivity is credited to strong phonon scattering leading to improved thermoelectric performance. Consequently, we attain a record Seebeck coefficient of ∼270 μV/K and power factor of ∼20 μW/(m·K2) that is almost two-order of magnitude higher as compared to conventional p-type transparent TE materials, indicating the potential of transparent γ-CuI thin films regarding its practical applicability in transparent thermoelectric devices. [ABSTRACT FROM AUTHOR]

Developing solid-state ionic conductors with desirable charge-transport efficiency and reasonable durability is a fundamental and long-lasting challenge for solid-oxide fuel cells (SOFCs). Ceria-based electrolytes, as one of the most common types of electrolytes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs), offer a high surface-exchange coefficient and faster kinetics in the triple phase boundaries (TPBs); however, they suffer to some extent of electronic conductivity in the reducing atmosphere and gradual phase transitions. Here in this work, we have reported a novel co-doped IT-SOFC electrolyte composite combining the apatite structure of Lanthanum Silicate (LSO) with the fluorite structure of Gadolinium-doped Ceria (GDC), which showed a high ionic conductivity and a minimal electronic leak. The resulting GDC-LSO composite electrolyte also achieved an OCV (open-circuit voltage) of 1 V at 800 °C, implying a significant improvement in the OCV values reported for the typical ceria-based electrolytes (∼0.75 V). The sample was prepared using 40 wt% GDC and 60 wt% LSO (40GDC-60LSO) showed a maximum electrical conductivity of 25 mS cm−1 at 800 °C with good densification properties (>95 % relative density). The cell electrochemical performance measurement was conducted using a 3.0 vol% humified H 2 stream at the anode side while the cathode side was exposed to the air at 800 °C. The interdiffusion of cations between La3+ in the LSO phase and Ce4+ and Gd3+ in the GDC phase was detected by XRD and EDX results after sintering samples at 1500 °C for 4 h using 0.5 wt% PVA or 0.5 wt% Ethyl cellulose (EC) as the binder. The proposed GDC-LSO composite could help better understand the influence of compositional constituents and processing variables on the densification and electrical properties of the electrolyte materials for the IT-SOFCs. [ABSTRACT FROM AUTHOR]

This study centers on the synthesis and characterization of a novel double perovskite, termed Sr 2 TiZrO 6 (STZO), which was synthesized using the conventional solid-state reaction method and subsequently calcined at 1000 °C for 12 h. X-ray diffraction (XRD) pattern refinement confirmed the formation of the tetragonal phase Sr 2 TiZrO 6 (space group P 4 mm), while both XRD and scanning electron microscope (SEM) analyses revealed that the resulting STZO displaying spherical-like grains with nanometric diameters. Thermogravimetric analysis revealed a minor weight loss attributed to the emergence of the ZrO 2 phase and the formation of the STZO double perovskite. The diffuse reflectance spectroscopy (DRS) results demonstrated strong UV-light absorption, with an optical absorption onset below 400 nm. The obtained band gap for direct transitions of the STZO sample is equal to 3.26 eV. The conductance and impedance study of the STZO sample are investigated. The present properties provide crucial insights to enhance comprehension of the STZO double perovskite material, which holds promise as a viable candidate for a range of applications, such as solar cells and photodiodes. [ABSTRACT FROM AUTHOR]

A series of Ba 0.75 Sr 0.25 Ti 1-x Zr x O 3 (x = 0, 0.01, 0.03, 0.05, and 0.1) ceramics were synthesized via a facile sol-gel route. The confirmation of a tetragonal structure was achieved through Rietveld refinement of the powder X-ray diffraction (XRD), and the finding was subsequently corroborated by Raman spectroscopy. The Scanning electron microscopy (SEM) confirmed the roughly cubical-shaped grains and average grain size is 0.31 μm for x = 0 and 0.70 μm for x = 0.05. The electrical properties such as dielectric constant, dielectric loss and ac/dc conductivity were investigated as a function of temperature and frequency. The Jonscher's universal power law (JPL) and Arrhenius equation have been used for the analysis of conductivity. The electrical conductivity variation at intermediate frequencies was explained using JPL. The Super-linear power law (SPL) explains the electrical response at higher frequencies. The temperature-dependent frequency exponents 's 1 ' and 's 2 ' were employed to predict the quantum mechanical tunneling (QMT), non-overlapping small polarons hopping (NSPT), and correlated barrier hopping (CBH) conduction mechanisms. [ABSTRACT FROM AUTHOR]

Ionic thermoelectric effect based on thermal migration of ion in the pore solution is emerging as a new branch of research on the thermoelectric effect of cement-based materials. However, the dense and tortuous pore structure of the cementitious materials may limit the ionic electrical conductivity and reduce the ionic thermal migration in pore solutions. Therefore, improving the pore structure may be a promising direction to enhance the thermoelectric effect of pore solution in cementitious materials. In this study, the pure cement paste with three water-cement ratios (w / c ratio = 0.3, 0.4, 0.5) and two curing methods (sealed curing and wet curing) are used. The effects of the ion concentration of the pore solution on the electrical conductivity and the Seebeck coefficient are investigated by the treatment of the vacuum saturation and the leaching process of the cement pastes. In addition, the pore structure of the cement paste is measured by mercury intrusion porosimetry (MIP). The effect of pore structure on the ionic thermoelectric effect of the cement pastes is studied. The results show not only the porosity and pore connectivity, but also the higher specific surface area of cement matrix is an important parameter for improving the ionic Seebeck coefficient of cementitious materials. The finer pore distribution in the cement matrix will cause a larger thermoelectric voltage. By improving the pore structure, the power factor (PF) of cement paste has been improved by two orders of magnitude, from 0.0027 μWm−1K−2 to 0.178 μWm−1K−2. The findings of this study can guide further understanding of the ionic thermoelectric effect of cementitious materials and provide a method for enhancing the thermoelectric effect of high-efficiency ionic thermoelectric materials (such as polyelectrolytes and ionic liquid) in cement matrix, which can develop ultra-high performance ionic thermoelectric cement-based materials for zero energy buildings. [ABSTRACT FROM AUTHOR]

In this research, Al/18Cu/3WC/3MoS 2 (wt.%) multilayered hybrid composites were fabricated by accumulative roll bonding (ARB), and their electrical and mechanical properties were investigated. After seven ARB cycles, an Al-matrix multilayered hybrid composite with a uniform distribution of WC-MoS 2 particles and Cu islands was achieved. The presence of the WC-MoS 2 particles and Cu islands significantly affected the electrical and mechanical properties of the fabricated composites. The composite obtained after seven ARB cycles showed an enhanced strength of 259 MPa. Also, it was found that the electrical conductivity of the Al matrix decreased by applied strain (about 19 % IACS) and the presence of the WC-MoS 2 particles. By annealing the fabricated composite obtained from final cycles, the electrical conductivity increased from 54 % IACS to 71 % IACS. [ABSTRACT FROM AUTHOR]

Planar heating elements employ carbon nanotubes, graphene, and metals. However, the high-temperature (300–500 °C) applications of heating elements based on metallic and organic materials are limited because they oxidize at high temperatures. Oxide materials such as RuO 2 are promising alternatives. The electrical conductivity of heating elements are strongly dependent on the aspect ratios of fillers; thus, RuO 2 nanosheets are suitable fillers for high-temperature planar heating elements because RuO 2 remains stable at high temperatures, and RuO 2 nanosheets have high aspect ratios of over 1000, as the lateral sizes and thicknesses of the RuO 2 nanosheets are 2∼5 μm and 1–3 nm, respectively. Consequently, the electrical conductivity of planar heating elements using RuO 2 nanosheets as fillers is 940 times higher than that of heating elements using conventional granular RuO 2 nanoparticles. Therefore, the RuO 2 nanosheet-based heating elements will be suitable in various applications requiring high temperatures and high uniformity. [ABSTRACT FROM AUTHOR]

Electrochemical co-deposition is a highly effective approach for achieving composites with specific composition and homogeneous distribution of reinforcement by manipulating electrolysis parameters. In this study, laminated carbon nanotubes reinforced copper composites (CNTs/Cu) were prepared through co-deposition and subsequent spark plasma sintering (SPS). In contrast to conventional powder metallurgy, the co-deposition method enables simultaneous deposition of CNTs and Cu particles while preserving the structural integrity of CNTs. It was observed that the CNTs were embedded within the growing Cu grains, resulting in a tightly bonded interface between them. The content of CNTs in composite deposited under current density of 0.5, 1.0 and 1.5 A⋅dm-2 is measured to be 0.51 vol%, 1.05 vol% and 1.31 vol%, respectively. The average grain size exhibited a significant reduction, decreasing from approximately 33.4 μm for pure Cu to 3.3 μm for the CNTs/Cu composite deposited under current density of 1.5 A⋅dm-2. Compared to pure Cu, the composite exhibited a significantly enhanced yield strength of 254 MPa, which is approximately 5 times that of pure Cu, the ultimate tensile strength improved to 290 MPa with an elongation of 15%, and the strengthening efficiency was calculated to be as high as 476. Load transfer is the primary contribution to the strength of the composites, followed by an increase in dislocation density and grain refinement. Meanwhile, the electrical conductivity of the composite with optimized condition demonstrated a high value of 94.4% IACS. The co-deposition method can facilitate the homogeneous dispersion of CNTs, enhance interfacial bonding, improve the structural integrity of CNTs, thereby enabling synergistic optimization of the properties of laminated CNTs/Cu composites. [ABSTRACT FROM AUTHOR]

The ceramic samples of Y 1-x Ca x Fe 0.5 Co 0 · 5 O 3 (x = 0.15, 0.25, 0.35) has been synthesized using solid-state reaction method. These samples exhibited orthorhombic perovskite structure and belonged to the Pbnm space group. X-ray analysis confirmed that Ca2+ ions replaced Y3+ ions at the A-site of perovskite structured YFe 0 · 5 Co 0 · 5 O 3 compound, while XPS studies confirmed the oxidation states of the constituent atoms. SEM micrographs and Williamson-Hall analysis showed that the crystallite size reduces with increasing Ca content, resulting in a strain-free, accommodated and stable microstructure. Complex impedance spectroscopic investigations established that the dispersion behaviors exhibited by the samples are due to Interfacial and Bulk polarizations. These phenomena are attributed to the accumulation of space charges and the hopping of electrons, respectively. Study further explore the semiconducting nature and negative temperature coefficient behavior of the material. Nyquist plots showed that grain interior is the major contributor to the conduction mechanism, while grain boundaries playing a secondary role. Correlated Barrier Hopping (CBH) has emerged as a suitable model to elucidate the conduction mechanism. The conduction process facilitated by CBH could potentially account for the observed negative permittivity in the material. [ABSTRACT FROM AUTHOR]

ZnO is one of the most promising mid-high temperature thermoelectric materials because of low cost, easy preparation and favorable chemical stability. Herein, the influence mechanism of Alkaline earth metal Ba doping on the thermoelectric properties of ZnO was studied. It is found that Ba doping can effectively improve the carrier mobility and electrical conductivity for that Ba doping can shorten the Zn–O bond and enhance the overlap and hybridization of electron orbitals. The electronic density of states of Zn and O is significantly enhanced. The highest power factor of ∼7.95 μWcm−1K−2 was obtained at 873 K, which is ∼1.4 times higher than that of the undoped sample. Due to the decrease of Young's modulus caused by Ba doping and the enhancement of phonon scattering of heavy element, the thermal conductivity decreases obviously in the whole temperature range. Ba doping enhanced the effect of phonon glass-electron crystal, and the ZT value of ∼0.345 was obtained at 873 K, which is ∼3.52 times as that of the pristine ZnO. The results indicated that alkaline earth metal doping is an effective way to improve the thermoelectric properties of ZnO functional materials. [ABSTRACT FROM AUTHOR]

In the last decades, NiO-GDC and NiO-SDC composites have emerged as interesting anodic materials for low and intermediate-temperature Solid Oxide Fuel Cells (SOFC) due to their high electrical conductivities and low activation energies. In this work, we report a simple and efficient Solution Combustion Synthesis (SCS) procedure for fabricating NiO-GDC and NiO-SDC nanocomposites with attractive physical properties for applications in low-temperature SOFC. The nitrate-fuel combustion method using citric acid as organic fuel was chosen due to its relatively low cost and good efficiency. Their potential electrical and mechanical performance for competitive SOFC anode technologies was assessed by characterizing disk-like compacted powders obtained by SCS. Two structurally optimized NiO-GDC and NiO-SDC disks were considered for the study of these properties, which presented good porosity and compaction degree. Vickers hardness tests show the good mechanical properties of both samples, achieving maximum hardness values of 4.7–6.7 [GPa] and validating the efficiency of the used compaction process. Electrical conductivity studies suggest an insulating-like behavior for both samples, evidenced by an increase in conductivity as the temperature increases. Good conductivities and low activation energies about of 10−2 [S/cm] and 0.18 [eV] were estimated for a low-temperature operation regime (400–600 °C), respectively, representing a highly competitive performance concerning similar composites typically reported in the literature. Results show the efficiency of our fabrication procedures to produce efficient and competitive NiO-GDC and NiO-SDC composites with projections for future large-scale manufacturing of low-temperature SOFC anodes. [ABSTRACT FROM AUTHOR]

The perovskite ceramics La 1- x Gd x BaCo 2 O 5+ δ with double lanthanide at A site was synthesized by a traditional solid phase reaction method. The structure and properties of La 1- x Gd x BaCo 2 O 5+ δ were investigated by experiment and analysis. It can be seen from the X-ray diffraction (XRD) that the crystal structure changes from single perovskite to double perovskite with the increase of Gd3+ content. Refined by Rietveld method, it is found that with the increase of Gd, the crystal structure of La 1- x Gd x BaCo 2 O 5+ δ oxides changes from cubic phase for x = 0 to tetragonal phase for x = 0.5 and then to orthorhombic for x = 1.0. The La 1- x Gd x BaCo 2 O 5+ δ ceramics shows good toxicity resistance in CO 2 and good thermal compatibility with Ce 0.9 Gd 0.1 O 2- δ (GDC) at 1100 °C. Through the X-ray photoelectron spectroscopy (XPS) test, it is found that this series of ceramic materials have good oxygen catalytic reduction activity, and the electronic conductivity is better than LaBaCo 2 O 5+ δ (LBCO) and GdBaCo 2 O 5+ δ (GBCO). Combined with the thermal expansion test and the electrochemical AC impedance analysis, it is found that the thermal expansion coefficient (TEC) of La 0.5 Gd 0.5 BaCo 2 O 5+ δ (LG-55) is closer to that of GDC electrolyte than LBCO, and the specific area resistance is smaller than GBCO. All these findings indicate that it can be used as a potential cathode material for intermediate-temperature solid oxide fuel cell (IT-SOFC). • A-site double-lanthanide La 1- x Gd x BaCo 2 O 5+ δ was prepared to integrate the merits of LaBaCo 2 O 5+ δ (LBCO) and GdBaCo 2 O 5+ δ (GBCO). • The prepared perovskite materials La 1- x Gd x BaCo 2 O 5+ δ demonstrate high electrical conductivity. • La 1- x Gd x BaCo 2 O 5+ δ (x ≤ 0.5) samples showed good thermal compatibility with Gd 0.2 Ce 0.8 O 2- δ (GDC) electrolyte. • La 0.5 Gd 0.5 BaCo 2 O 5+ δ has relatively best corrosion resistance to CO 2. [ABSTRACT FROM AUTHOR]

Three borosilicate glass samples of 25 % Si 2 O – 30 % Na 2 O – 45 % B 2 O 3 doped with x Dy 2 O 3 (where x = 0, 2, and 4 mol %) were prepared using the melt quenching technique. Photoluminescence spectra for glass samples were studied when excited by 350 nm in the 400–800 nm range, where emission sharply increases for samples doped with 2 % Dy 2 O 3 (BSNDy2) at 580 nm after exposed to 30 kGy. Also, glass containing 2 % Dy photoluminescence constants, such as decay curves CIE chromaticity, was measured for all samples that gave three decay behaviors: slow, intermediate, and fast. Experimental lifetime (τ exp.), color coordination (X, Y), and yellow/blue intensity ratio (y/b) beside the color correlated temperature (CCT) were determined before and after being irradiated by 30 and 60 kGy from γ ray source where the y/b ratio of BSNDy2 increase by increasing exposure to gamma doses and were >1. In addition, electrical conductivity at different temperatures was investigated as the BSNDy2 sample gave the highest conductivity and decreased by BSNDy4. Moreover, shielding parameters such as the tenth value layer, half value layer, mean free path and mass attenuation coefficient values were calculated at different gamma-ray energies via the Phy-X program, showing the highest values for MAC, Z eff , N eff, and C eff for BSNDy4 sample. The findings showed that adding Dy 2 O 3 to the glass gave a fortified shielding character. [ABSTRACT FROM AUTHOR]

Electrical conductivity is one of the most important concerns in spinel-structured antioxidant films coated on a solid oxide fuel cell separator, and the mechanism of electrical conduction involves the small polaron hopping through corner-shared octahedral sites. Arranging favorable ions in the octahedral sites rather than in the tetrahedral sites is better for achieving higher electrical conduction. In this study, Zn, which prefers the tetrahedral site, was substituted for the Mn 1.5 Co 1.5 O 4 spinel to arrange site distribution. The crystal structure, electrical conductivity, and thermal expansion behavior of Zn-substituted ZMCOs [Zn x Mn 1.5−0.5x Co 1.5−0.5x O 4 (0.0 ≤ x ≤ 0.6)] were investigated. At Zn = 0.2, the highest electrical conductivity of 42.1 S/cm was observed, while at Zn > 0.2, the electrical conductivity decreased due to decreased Co2+/CoIII and Mn3+/Mn4+ pair concentration because Zn ions started to occupy the octahedral site. The higher the Zn concentration of ZMCO, the lower the distortion of the MnO 6 octahedron via the Jahn–Teller effect, resulting in a higher symmetry of the crystal structure. Therefore, with the increase in the Zn concentration, a mixture of tetragonal-cubic phase changed to cubic phase. In addition, the phase transition temperature of the tetragonal-cubic phase decreased. [ABSTRACT FROM AUTHOR]

Presently, the formation of oxide films on the surface of Ti-based bipolar plates results in decreased electrical conductivity. This limitation frequently curtails the operational lifespan of proton exchange membrane fuel cells (PEMFCs). In this study, we engineered Ti alloy bipolar plate materials using an elemental screening process and validated their performance through experimentation. The elemental screening results identified eight elements, specifically Ni, Cr, Mo, Ta, W, Fe, Co, and Zn, as promising candidates for bipolar plate materials. Among these, Mo exhibited a pronounced affinity for incorporation into the TiO 2 oxide film. Conductivity measurements of passivated bipolar plates indicated that the Ti–Mo alloy displayed excellent electrical conductivity (1.699 × 1020 Ω m−1). Notably, the introduction of Mo (with an energy level of 1.64 eV) significantly reduced the band gap of the oxide film. Importantly, even after continuous potential oxidation for 10,000 s, the interfacial contact resistance (ICR) of Ti-0.35Mo (9.80 mΩ cm2) remained below the threshold set by the American DOE standard (ICR <10 mΩ cm2). Consequently, this research successfully devised a bipolar plate material utilizing a Ti–Mo alloy and proposed an innovative strategy for improving the conductivity of oxide films in bipolar plate materials via an elemental screening approach. [ABSTRACT FROM AUTHOR]

Soft ferrite nanoparticles with the composition Cd 0.4 Zn 0.6-x Co x Fe 1.9 Sm 0.1 O 4 , where x = 0.0, 0.2, 0.4, and 0.6, were effectively prepared using the green synthesis method. The cubic spinel structure of the produced soft ferrite was verified by X-ray diffraction investigation. For the various values of x, it was found that the average crystallite size and lattice constant varied between 34.50 nm and 27.28 nm and 8.5942 Å and 8.4479 Å, respectively. Images from scanning electron microscopy revealed the occurrence of aggregation and fine grain growth. An energy-dispersive X-ray spectroscopy investigation was employed to further confirm the ferrites composition. Tetrahedral absorption bands and metal ion-related absorption modes were found in Fourier-transform infrared spectra. As x changed from 0.0 to 0.6, the optical band gap energy (E g) showed a declining trend from 3.50 eV to 2.57 eV. Additionally, when the quantity of Co2+ increased, the DC electrical resistivity dropped from 5.0475 × 107 Ω cm to 4.3143 × 106 Ω cm. The dielectric characteristics, such as impedance, dielectric losses, and dielectric constant, showed a progressive decline with frequency. Notably, at high frequencies, the specimen Cd 0.4 Zn 0.2 Co 0.4 Fe 1.9 Sm 0.1 O 4 showed the greatest dielectric constant. The behavior of saturation magnetization was growing, and the estimated squareness values (S.Q., or Mr/Ms < 0.5) represent the ability of magneto-static interaction. Based on these characterization results, the synthesized soft ferrites are suitable for use in transformer cores, telecommunications equipment, and microwave devices. [ABSTRACT FROM AUTHOR]

Double perovskite materials are greatly appealing because of their multiferroic properties. Among such materials, double perovskite with rare earth metals are widely studied by researchers. Presently, the double perovskite La 2 NiMnO 6 (LNMO) samples are synthesized using the hydrothermal method by varying the concentration of the solvent (NaOH). The Powder X-ray diffraction analysis confirmed the formation of monoclinic structure with the P2 1 /n space group for prepared LNMO samples. The SEM image of the prepared samples revealed a cube-like structure. The impedance, dielectric, AC conductivity and modulus are studied in a wide frequency range from 100 Hz to 5 MHz to analyse the electrical and microstructure properties of the synthesized LNMO samples. The presence of a non- Debye type of relaxation peak is confirmed by impedance, dielectric and modulus studies. The effect of grains and grain boundaries are analysed by the Nyquist plot and the polarization of the materials are explained by the Maxwell-Wagner interfacial polarization model and Koop's theory. Using a three electrode system, the electrochemical behaviour of prepared LNMO samples are studied in various concentration of electrolyte (KOH) at different scan rates and found to have a pseudocapacitive nature. The highest specific capacitance value for LNMO10 is 44.60 F/g, LNMO20 is 50.14 F/g and LNMO30 is 25.81 F/g at a scan rate of 10 mV/s for 3 M KOH. The room temperature magnetic behaviour of synthesized LNMO samples analysed by Vibrating Sample Magnetometer paves way for magnetic storage applications. [ABSTRACT FROM AUTHOR]

Due to its excellent electrical conductivity and stable Magnéli phase structures, cermet Ti 4 O 7 has emerged as one of the most promising materials in the fields of electrochemical application. However, the difficulties in creating high specific surface area structures, having room for conductivity enhancement when used as a conductive additive, and passivation forming TiO 2 under sufficiently oxidizing conditions limit the development of Ti 4 O 7 for practical applications. In this work, the V-doped Ti 4 O 7 hollow spheres with improved electrical conductivity and thermal stability were synthesized by the three-step approach of solvothermal reaction, oxidative crystallization, and hydrogen reduction without any surfactant or template. The formation mechanism of hollow (Ti,V) 4 O 7 was revealed by analyzing the valence evolution of V and comparing the morphology of Ti 4 O 7. The conductivity of Ti 4 O 7 and (Ti,V) 4 O 7 was compared and contrasted as functions of pressure, demonstrating the superiority of (Ti,V) 4 O 7 in terms of conductivity. Thermograms showed that the addition of V increased the complete oxidation temperature of Ti 4 O 7. Moreover, the reason for the enhanced electrical conductivity and thermal stability of V-doped Ti 4 O 7 was also revealed based on density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

This research is focused on designing new ceramic oxides with the spinel structure for a potential application as sensitive temperature and magnetic field sensors. In this respect, the mixtures of ferrimagnetic NiFe 2 O 4 with low-resistive Ni 0.66 Cu 0.41 Mn 1.93 O 4 semiconductor (molar coefficient α = 1 / 5 and 1 / 2) were prepared using the chemical co-precipitation technique followed by a low-temperature sintering of the cold-pressed powders. For the prepared materials, a variation of the electrical conductivity σ dc with temperature T (in the range 50 K–400 K) is quantitatively analyzed using different theoretical concepts of the charge carrier hopping transport occurring in disordered materials with strong electron-phonon interaction. It has been shown that an increase in α from 0 to 1 / 2 causes a step-like change of the dc electrical conductivity and, simultaneously, a gradual change in the magnetization M determined in the saturation state. The temperature coefficient of resistance T C R of the prepared ceramics takes the values from −0.6%/K (at 400 K) to −19.6%/K (below 100 K). The highest absolute value of the magneto-resistance coefficient M R determined at 150 K (and at magnetic field 7 T) registered for ceramic oxide with α = 1 / 2 was found to be 3.4%. [ABSTRACT FROM AUTHOR]

Attrition-milling process has been applied to Ce-doped CaMnO 3 precursors to obtain small grain-size powders. The use of Ce4+ as dopant instead a Rare Earth3+ has allowed decreasing by 50% the atomic proportion of dopant, to obtain equivalent charge carrier concentration, which is required for attaining promising properties for thermoelectric applications. An impressive decrease in thermal processing time was achieved, together with an increase in thermoelectric performances, when compared to classically prepared materials. XRD and SEM analysis have confirmed that the final material is nearly single phase. Moreover, grain sizes and density increase with the sintering duration. These microstructural differences are reflected in a significant decrease in electrical resistivity, when compared to the samples prepared from ball-milled precursors (used as reference), without drastically modifying the Seebeck coefficient values. On the other hand, despite of their high electrical conductivity, thermal conductivity is decreased for short time sintered materials, leading to the highest ZT values at 800 °C (∼0.27) in samples sintered for 1 h at 1310 °C. These values are among the best reported in the literature, but they have been obtained in very short time using a simple, and easily scalable process. The suggested approach presented in this work appears particularly promising for large-scale production of oxide-based thermoelectric modules for power generation. [ABSTRACT FROM AUTHOR]

High entropy materials offer optimal conditions for regulating and modifying new material properties due to their vast composition space. Through traditional solid phase sintering, this article successfully synthesized a series of Sr(Ti 0.2 Zr 0.2 Y 0.2 Sn 0.2 Hf 0.2 Sc 0.2x)O 3-σ high entropy perovskite oxides with varying Sc3+ doping concentrations and comprehensively investigated the microstructure morphology, crystal structure, and electrical conductivity of Sc-doped HEPs as well as their influence on oxygen transfer rate. The results demonstrate the successful incorporation of Sc3+ into the high entropy lattice, resulting in a transformation of the crystal to a positively cubic structure with enhanced reciprocity. While the lattice vibration of BO 6 octahedron is weakened by the introduction of Sc3+, it has no impact on the phase stability of the crystal structure. Moreover, The results of the electrochemical impedance spectroscopy test demonstrate that at a temperature of 750 °C, with a doping amount of Sc3+ at 0.14, the conductivity (σ) of Sc3+ is measured to be 5.74 × 10−3 S/cm, exhibiting an increase of 61.7% compared to non-doped samples. Correspondingly, the activation energy (Ea) is reduced from 0.51 eV to 0.39 eV as well. This doping strategy effectively expands the potential applications of high entropy perovskite oxides in solid oxide fuel cells (SOFCs). These findings serve as a driving force for further investigation into high entropy ceramics of the strontium series that exhibit optimal properties. [ABSTRACT FROM AUTHOR]

The present investigation was carried out to develop dense ceramics of silicon nitride-titanium nitride (Si 3 N 4 –TiN) with low electrical resistivity and excellent mechanical properties. The objective was to employ these ceramics as substrates of conductive diamond electrodes produced by chemical vapor deposition (CVD) for electrochemical applications. TiN powder was added to a Si 3 N 4 matrix powder composition at varying volume fractions (21–30%). Disc-shaped samples were fabricated by mixing and pressing the powders, followed by pressureless sintering. The crystalline phase composition and microstructure were analyzed using X-ray diffraction and scanning electron microscopy, while the electrical resistivity was measured with a four-point probe configuration. The composites transitioned from insulating to conductive behavior between 23 and 27%vol TiN. The developed compositions displayed superior hardness, fracture toughness, elastic modulus, and thermal conductivity compared to the Si 3 N 4 matrix. Notably, the composition containing 30%vol TiN displayed noteworthy properties, including a hardness value of 16.1 GPa, fracture toughness of 7.0 MPa m1/2, and electrical resistivity of 8.9 × 10−1 Ω cm. Finally, the proof-of-concept experiment demonstrated the potential of Si 3 N 4 –TiN composites as robust and electroconductive substrates for depositing conductive diamond electrodes. This was achieved by successfully depositing conductive diamond films on Si 3 N 4 –TiN substrates using the Hot Filament Chemical Vapor Deposition (HFCVD) technique. [ABSTRACT FROM AUTHOR]

Geopolymer has potential advantage in electrical conductivity. The conductive and mechanical properties of engineered geopolymer composite (EGC) with carbon fiber (CF) and nano-carbon black (NCB) were studied respectively in this paper. Firstly, the percolation thresholds of CF and NCB were determined, and then the effect of curing age, moisture content and temperature on the conductivity were analyzed. The fluidity, compressive and flexural strengths and tensile ductility were also analyzed. Finally, the conductive behaviors were studied by combing electrochemical impedance spectroscopy (EIS) and equivalent circuit model. The results indicate that the higher the dosage, the better the conductivity, the percolation thresholds of CF and NCB are 0.05 vol% and 15 vol%. Curing age, moisture content and temperature have important effects on the conductivity, but the effects are restricted by the dosage of conductive fillers. The more the dosage of the CF, the smaller the effect, while the NCB has little limited effect. CF and NCB also have important effects on the mechanical properties and the CF-EGC and NCB-EGC still have high ductility. Finally, an equivalent circuit model is proposed which can well characterize the conductive behaviors under different conditions. [ABSTRACT FROM AUTHOR]

Sr–deficient Sr 2– x MgMoO 6– δ (SMM x) (x = 0.00–0.25) double perovskites were prepared using the sol–gel process. XRD results indicate that the x = 0.00–0.15 samples are pure phases with good redox stability, while trace SrMoO 4 impurity was detected for the samples with x ≥ 0.20. XPS analysis demonstrates that Mo5+ content increases monotonously with Sr–deficiency, and the increasing number of Mo5+/Mo6+ redox pairs enhances electrical conductivity with increasing x. Among the SMM x compositions, the SMM0.15 anode exhibits optimal electrochemical performance, with polarization resistance attaining a minimum of 0.36 and 0.59 Ω cm2 in H 2 and CO, respectively, at 850 °C. Using SMM0.15 as the anode skeleton, Cu nanoparticles were loaded onto the skeleton surface via nitrate impregnation. The resulting Cu–impregnated SMM0.15 composite anodes exhibited significantly improved electrical and electrochemical properties. Peak power densities of a single cell supported by a 300–μm–thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ electrolyte and a twice Cu–impregnated SMM0.15 composite anode achieve 933 mW cm−2 in H 2 and 415 mW cm−2 in CO at 850 °C. The electrochemical reactions at the anode were mainly dominated by fuel diffusion and adsorption/disassociation, particularly for CO. The good cell stability in both H 2 and CO further demonstrates that Cu–impregnated SMM0.15 has great potential as an anode candidate for SOFCs. [ABSTRACT FROM AUTHOR]

The effects of hafnium removal on the sinterability, phase composition, and microstructural, mechanical, and electrical properties of 8YSZ (8 mol% yttrium stabilized zirconia) were investigated using SEM, XRD, Raman spectroscopy, EBSD, three-point bending, Vickers indentation, and impedance spectroscopy. The 8YSZ and 8YSZ 0 (8 mol% yttrium-stabilized hafnium-free zirconia) ceramics were prepared via dry pressing and atmospheric sintering, respectively. The overall mechanical properties of the 8YSZ 0 ceramic were poor. However, at a sintering temperature of 1450°C, the relative density of 8YSZ and 8YSZ 0 ceramics was almost identical. 8YSZ 0 had a slightly smaller grain size and activation energy, and its electrical properties were slightly better than those of the 8YSZ ceramics. The presence of tetragonal secondary phases in the cubic structure of 8YSZ ceramics inhibited crack propagation and led to an increase in the mechanical properties and a decrease in the ion conductivity. In terms of the crystal structure, the increase in the cubic phase lattice parameters and tetragonal phase c/a values of the 8YSZ 0 ceramics was attributed to the larger Zr4+radius, reduced local lattice distortion, and increased matrix oxygen vacancy concentration and cubic phase content. The EBSD analysis results indicated that there was no significant difference in grain orientation between the two types of ceramics, but the content of 8YSZ ceramics in large angle grain boundaries was slightly higher, especially in special grain boundaries Σ3 and Σ9. Therefore, this material can be used as a solid-state electrolyte candidate. [ABSTRACT FROM AUTHOR]

Present study explores the structural, electrical and transport properties of dysprosium cation (Dy3+) substitution on (Fe+3) site in cobalt nonoferrites [CoFe 2-x Dy x O 4 (Dy(x) = 0.00, 0.05, 0.10 & 0.15)] prepared by sol-gel chemical route. X-ray diffraction pattern confirms the pure cubic spinel structure for all samples. The average crystallite size was found in the range of 49 to 72 nm with no linear variation with incresing doping concentration of (Dy3+) ions. The values of lattice parametres is found to be changed from 8.34 to 8.39 Å for pristine cobalt nanoferrite (CoFe 2 O 4) and sample having highest doping concentration i.e. Dy(x) = 0.15 respectively. The porosity observed to be decrease linearly with increasing (Dy3+) ion concentration. The electrical properties have been investigated by analyzing dielectric behaviour in the frequency range of 75 kHz- 5 MHz and temperature range of 100K– 400K. The frequency dependent dielectric behaviour at different temperatures is explained in terms of Maxwell–Wagner and Koop's phenomenological models. Ferrite with Dy(x) = 0.15 have achieved highest dielectric constant in the range of 441 to 5234 which was measured at 100K (5 MHz) and 400K (75 kHz) respectively. The electrical resistivity of each of the ferrite sample reduces with rising temperature representing the semiconductor behaviour of all ferrites which is due to the thermally triggered charge carriers hopping between (Fe2+) and (Fe3+) ions and associated with higher drift mobility. The increase in drift mobility at room temperature with increasing (Dy3+) ion concentration is considered to be a sign of improved transport behaviour. The high value of dielectric constant and low dielectric loss of all these ferrites make them suitable for the memory storage devices. [ABSTRACT FROM AUTHOR]

In this paper, the crystal structure and electronic structure of Ti 4 O 7 were calculated based on density functional theory, and Magnéli phase Ti 4 O 7 bulks were successfully prepared by spark plasma sintering (SPS). Results indicated that the contribution of Ti 3 d to Fermi level increased due to the lack of oxygen atom in lattice, and the energy band gap of Ti 4 O 7 was reduced compared with that of TiO 2. By calculating the relationship between the densification rate and effective stress in the process of SPS, it can be known that the densification mechanism of Ti 4 O 7 powders was controlled by diffusion. Based on this, under the conditions of sintering temperature of 1000 °C, holding time of 10 min and sintering pressure of 30 MPa, Ti 4 O 7 bulks with the optimal electrical conductivity (961.5 S cm−1) could be obtained, which was more than 30% higher than the graphite material reported in literature. The results reveals that Ti 4 O 7 will be one of the most promising electrode materials in the electrochemical field. [ABSTRACT FROM AUTHOR]

(Ti/Zr/Hf)CoSb 0.8 Sn 0.2 compounds are promising p -type thermoelectric materials. In this work, excessive Ga and Co deficiencies were introduced into Ti 0.2 Hf 0.8 CoSb 0.8 Sn 0.2 compounds. The microstructure, electrical, and thermal transport properties were investigated in the temperature range of 300 K < T < 1000 K. The excessive Ga formed nanoinclusions with Ti and Sn at the grain boundaries. The Co deficiencies lowered the thermal conductivity and simultaneously improved the electrical conductivity. As a result, the power factor was enhanced to 3.2 mW/m K2, and the maximum Z.T. of ∼0.93 at 988 K was obtained in the Ti 0.2 Hf 0.8 Co 0.99 Sb 0.8 Sn 0.2 –0.01Ga sample, which is an increase of ∼48% compared to that of the pristine Ti 0.2 Hf 0.8 CoSb 0.8 Sn 0.2 sample. [ABSTRACT FROM AUTHOR]