•The (In, Nb) co-doped BaTiO3 ceramics were prepared via solid-state reaction method.•The dual doping improved dielectric constant.•The dual doping leads to lower Curie temperature.•The dual doping leads to reduced concentration of oxygen vacancies.BaTi1-x(In0.5Nb0.5)xO3 (x = 0, 0.01, and 0.03) ceramic samples were prepared using the conventional solid-state reaction method. The dielectric properties of these samples were investigated as a function of temperature (300 K ≤ T ≤ 700 K) and frequency (102 Hz ≤ f ≤ 106 Hz). Great enhancement of dielectric constant in the dual doped samples was found. Defect diploles of [NbTi5+-Ti3+] and [NbTi5+-InTi3+] were suggest to account for the enhancement of dielectric constant.

BaZrO3 (BZO) powders were synthesized by solution combustion based on the glycine nitrate process. The sintering conditions of the BZO sample were optimized by varying the sintering temperature and dwell time. The dielectric properties of the sintered samples were investigated in the temperature range of 300–1080 K and frequency range of 102 to 106 Hz. The sample sintered at 1973 K for 12 h was found to show the best dielectric properties. Detailed investigations on this sample reveal an incipient ferroelectric behavior in the temperature range below 420 K and a colossal dielectric behavior above 420 K. The colossal dielectric behavior is composed of two thermally activated relaxations. The low-temperature relaxation was argued to be a dipolar relaxation caused by an oxygen vacancy hopping motion inside grains and the high-temperature one was ascribed to a Maxwell–Wagner relaxation due to the oxygen vacancies being blocked by the sample/electrode contacts.

KTaO3 ceramic samples were prepared via a conventional solid state reaction route. The dielectric properties of KTaO3 were investigated in temperatures from room temperature to 1000 K and the frequency range of 102–106 Hz. The sample exhibits an abnormal dielectric behavior contrary to the traditional thermally activated behavior in the temperature range below 450 K. Our results revealed that the sample was very sensitive to humidity, leading to a metal-insulator transition (MIT) at 473 K. It is the positive temperature coefficient of resistance of the MIT that results in the abnormal dielectric behavior. When the temperature is higher than 500 K, the sample shows two normal dielectric relaxations following thermally activated behavior. The low- and high-temperature relaxations were argued, respectively, to be related to dipolar relaxation and Maxwell–Wagner relaxations due to oxygen vacancies hopping inside grains and then being blocked by grain boundaries.

Catalyst layers derived from La2NiO4, LaNiO3 and Ni/La2O3 precursors were applied to a conventional Ni-based anode in a proton conducting solid oxide fuel cell (H+-SOFC) for the dry reforming of methane with CO2. The phase structures, microstructures and catalytic activities of catalysts from the different precursors were systematically investigated. The cell performance and durability of a H+-SOFC with a catalyst layer (layered H+-SOFC) were examined. The layered H+-SOFC had higher cell performances than the conventional H+-SOFC. However, catalyst deactivation and degradation of the cell performance were observed as carbon deposition occurred on the catalyst layer due to CO disproportionation in exhaust gas at a high partial pressure of CO. The structure of carbon deposited on the catalysts was also investigated.

•The BaZr0.8Y0.2O3-δ ceramics were prepared via glycine nitrate process.•Three sets of relaxations (R1, R2 and R3) were observed.•R1 was ascribed to be a dipolar relaxation resulting from the OHO•-Y dipole.•R2 and R3 were argued to be Maxwell-Wagner-type relaxation.Ceramic samples of BaZr0.8Y0.2O3-δ (BZY) were synthesized by solution combustion based on the glycine nitrate process. The dielectric properties were investigated in the temperature range of 300–870 K and frequency range of 102–106 Hz. Two types of carriers, hydroxyl ions and oxygen vacancies, coexist in the material and lead to three sets of relaxations. The activation energies were calculated to be 0.50, 0.65, and 1.27 eV for low-, middle- and high-temperature relaxations, respectively. The low-temperature relaxation was ascribed to be a dipolar relaxation resulting from the OHO•-Y dipole. The middle- and high-temperature relaxations were argued to be Maxwell-Wagner relaxations associated with space charges caused by hopping oxygen vacancies blocked by grain boundaries and sample-electrode contacts, respectively.

We herein reported colossal dielectric constant (CDC) behavior in GaAs single crystals. This behavior appears in the temperature range above room temperature and results from the bulk effect due to polaron relaxation caused by hopping motion of EL2 defects. When temperature rises higher than 420 K, the interfacial contribution due to Maxwell–Wagner relaxation caused by sample/electrode contacts appears. When temperature is higher than 560 K, the CDC behavior is mainly contributed by the interfacial effect. These features are quite different from the CDC behavior found in oxides, and therefore, the CDC behavior in GaAs single crystals is considered as a new type of the CDC family. Our results underscore the role of point-defects in CDC behavior and suggest that defect engineering can be a promising strategy to achieve superior CDC behavior in both oxide and non-oxide materials.

•Dy2Ti2O7 ceramics was prepared by solid-state reaction method.•Incipient ferroelectricity was confirmed for Dy2Ti2O7 sample.•Dy2Ti2O7 shows two successive relaxations between 450 K and 973 K.•These relaxations are conduction relaxations appearing due to hopping motions of oxygen vacancies.Dy2Ti2O7 ceramic samples were prepared via the solid-state reaction route. The dielectric properties of the sample were systematically investigated in the temperature range from 4 K to 973 K and the frequency range of 100 Hz to 1 MHz. Both Raman and low-temperature (down to 4 K) dielectric measurements indicate incipient ferroelectricity in the Dy2Ti2O7 sample. In addition, two relaxations were observed in the temperature range above 450 K. Our results indicate that the two relaxations are related to conductivity relaxation associated with singly and doubly ionized oxygen vacancies.

•We have developed a facile approach to synthesize the Fe3S4 nanosheets.•The products show large specific surface area and ferromagnetic behavior.•The Fe3S4 nanosheets exhibit superior electrochemical performances.Transition metal chalcogenides have attracted much attention owing to their unique properties and various potential applications. However, it is rather challenging to explore a facile and versatile strategy to synthesis of Fe3S4 nanosheets. In this paper, we have developed an easy and controllable method to prepare large-scale Fe3S4 nanosheets, which have unique morphology, large specific surface area, and ferromagnetic behavior. The growth process of Fe3S4 nanosheets has been investigated based on the results of time-dependent experiments. When they were employed as anode materials for lithium-ion batteries, the Fe3S4 nanosheets can deliver stably reversible capacity of 548 mA h g−1 after 120 cycles at a current density of 0.2 A g−1 and superior rate performance.

ZnNb2O6 ceramics were prepared via conventional solid-state reaction route. The dielectric properties of ZnNb2O6 were investigated in the temperature range from room temperature (RT) to 700 °C and frequency range of 103 − 2 × 106 Hz. Our results revealed that the sample exhibits an intrinsic dielectric response with a dielectric constant of ∼20.9 below 150 °C followed by two thermally activated relaxations (R1 and R2) at higher temperatures. Both R1 and R2 are related to oxygen vacancies inherent in the sample. At temperatures higher than ∼550 °C, an external relaxation (R3) induced by dc bias was observed. By means of the dielectric permittivity, electric modulus, impedance and admittance, R1 was attributed to be a dipole-type relaxation due to the hoping motions of oxygen vacancies. R2 and R3 were ascribed to be a Maxwell-Wagner-type relaxation resulting from the space charge due to the hoping vacancies blocked by grain boundaries and electrodes, respectively.

•CaLaAlO4 ceramic samples were prepared via solid state reaction method.•Giant dielectric behavior was observed in CaLaAlO4.•The Giant dielectric behavior results mainly from the interfacial relaxation.CaLaAlO4 ceramic samples were prepared by solid state reaction. The low-frequency (20–107 Hz) dielectric properties were investigated in the range from room temperature to 700 °C. It was found that the CaLaAlO4 ceramic samples show giant dielectric behavior above 100 °C. The behavior is composed of two thermally activated dielectric relaxations. The low-temperature relaxation is caused by the bulk response related to the hopping motion of oxygen vacancies, and the high-temperature one is an interfacial relaxation due to grain boundaries. Our results revealed that the giant dielectric behavior is mainly caused by the interfacial relaxation.

•Samples of Gd2O3-doped CeO2 ceramics were fabricated by the co-precipitation method.•Three thermally activated dielectric relaxations were observed.•The relaxations are related to the bulk, grain boundary and contact effect.Ceramic samples of Gd2O3-doped CeO2 (GDC) were fabricated by the co-precipitation method. The dielectric properties were investigated as functions of temperature (350–950 K) and frequency (100 Hz to 10 MHz). Three relaxations with the activation energies of 0.76, 0.88, and 1.03 eV in the order of ascending temperature were observed in GDC. The low-, middle-, and high-temperature relaxations are argued to be related to the bulk response caused by the Gd dopant-oxygen vacancy pairs, grain boundary, and contact effects, respectively.

The effect of manganese doping on the dielectric properties of CaCu3Ti4-xMnxO12 (x = 0, 0.02, 0.04) were investigated over a broad temperature range (93–723 K) in the frequency range from 100 Hz to 10 MHz. Two dielectric relaxations and two dielectric anomalies were observed. The low-temperature relaxation appearing in the temperature range below 200 K is the characteristic relaxation for CaCu3Ti4O12. This relaxation was attributed to the polaron relaxation due to electron hopping between Ti3+ and Ti4+ states. Due to the negative factors of notable decreases in the Ti3+/Ti4+ and Cu3+/Cu2+ ratios and the concentration of oxygen vacancies as revealed by X-ray photoemission spectroscopy, Mn-doping was found to gradually destroy rather than move this relaxation to a higher temperature. The high-temperature relaxation occurring around room temperature was found to be a Maxwell-Wagner relaxation caused by grain boundaries. Our results confirm that the colossal dielectric behavior in the tested samples results from both polaron and Maxwell-Wagner relaxations, but is predominated by the latter relaxation. The low-temperature anomaly behaves as a phase-transition-like behavior. It was argued to be created by oxygen vacancies transition from static disorder to dynamic disorder. The high-temperature anomaly is an artificial effect caused by negative capacitance.

•The La2Ti2O7 ceramics were prepared by conventional solid-state reaction method.•The LTO shows an intrinsic dielectric response (εr ∼ 57) under 250 K.•The sample successively shows three relaxations from 250 K to 1073 K.•The low-temperature relaxation is a polaron relaxation caused by hopping holes.•The other two relaxations are conduction relaxation due to hopping motions of OVs.La2Ti2O7 ceramic samples were prepared via conventional solid-state reaction route. The dielectric properties of La2Ti2O7 were investigated as functions of temperature (113–1073 K) and frequency (100 Hz–1 MHz). Our results revealed that La2Ti2O7 ceramics exhibit intrinsic dielectric response with a dielectric constant of ∼57 in the temperature range below 250 K. Three thermally activated dielectric relaxations were observed when the temperature higher than 250 K. The low-temperature relaxations R1 with the activation energy of 0.38 eV is found to be a polaron relaxation results from hopping holes. The high-temperature relaxations R2 and R3 are related to the conduction progress associated with the singly and doubly ionized oxygen vacancies, respectively.

Hollow metal chalcogenides have attracted increasing attention in recent years owing to their widespread applications. However, to the best of our knowledge, the effective synthesis of a uniform Fe3S4 hollow nanostructure for fundamental research and practical application has not been reported to date. In this paper, a facile method for preparing nanostructured Fe3S4 with controlled hollow spheres was developed. The as-prepared Fe3S4 shows ferromagnetic characteristic and porous nature. Their Li ion storage and water treatment performances are further tested. Such mesoporous hollow spheres exhibit a highly reversible capacity of 750 mA h g−1 over 100 cycles at a current density of 0.2 A g−1. In addition, when used as an adsorbent, the Fe3S4 exhibited high adsorption capability and the adsorption isotherms are subject to the Freundlich equation. This work not only presents a facile strategy for the synthesis of novel Fe3S4 hollow spheres but also supplies a promising advanced material for lithium-ion batteries and water treatment.

•SCCN exhibits sufficiently high electronic conductivity and excellent chemical compatibility with SDC electrolyte.•Highly charged Ce4+ and Nb5+ successfully stabilize the perovskite structure.•The ASRs of the SCCN–SDC cathode are 0.027 and 0.049 Ω cm2 at 700 and 650 °C, respectively.•SCCN is promising as a cathode material for ITSOFCs.Sr0.9Ce0.1Co0.9Nb0.1O3−δ (SCCN) has been synthesized using solid state reaction, and investigated as a new cathode material for intermediate temperature solid oxide fuel cells (ITSOFCs). SCCN material exhibits sufficiently high electronic conductivity and excellent chemical compatibility with SDC electrolyte. Highly charged Ce4+ and Nb5+ successfully stabilize the perovskite structure to avoid order–disorder phase transition. The electrical conductivity reaches a high value of 516 S cm−1 at 300 °C in air. The area specific resistances of the SCCN-50 wt.% Ce0.8Sm0.2O1.9 (SDC) cathode are as low as 0.027, 0.049, and 0.094 Ω cm2 at 700, 650, and 600 °C, respectively, with the corresponding peak power densities of 1074, 905, and 589 mW cm−2. A relatively low thermal expansion coefficient of SCCN–SDC is 14.3 × 10−6 K−1 in air. All these results imply that SCCN holds tremendous promise as a cathode material for ITSOFCs.

Nanoscale porous metal–organic frameworks and related materials have received considerable attention in recent years due to their widespread applications. However, the effective synthesis of magnetic core–shell MOFs still remains a significant challenge. In this article, a Fe3O4@ZIF-8 core–shell nanostructure with unique morphology, a large specific surface area, excellent thermal stability, and superparamagnetic properties is reported. Additionally, instead of using organic surfactants, a surfactant-free and facile synthesis route is successfully developed. The ZIF-8 shell thickness can be precisely controlled by altering the number of growth cycles. Fe3O4@ZIF-8 shows good adsorption properties for MB, with maximum adsorption capacity of 20.2 mg g−1.

•Mesoporous yolk–shell magnetic magnesium silicates have been prepared.•The yolk morphology and shell thickness can be readily tunable.•The products have large specific surface and unique mesoporous structure.•The excellent properties for the removal of methylene blue were studied.Yolk–shell structures have attracted intensive interest owing to their unique structure and promising applications in various fields. In this study, we report a facile, effective route to prepare tubular/spindle mesoporous yolk–shell magnetic magnesium silicate. The yolk morphology and shell thickness can be readily tunable by varying the experimental conditions. The as-synthesized products have large specific surface and unique mesoporous structure. The adsorption capacities of tubular and spindle mesoporous yolk–shell magnetic magnesium silicate for methylene blue are 188 and 141 mg/g, respectively.

•Both Al and Nb vacancies could induce ferromagnetism in Sr2AlNbO6Sr2AlNbO6.•Ferromagnetism driven by Al vacancy originates from the 2px state of nearest O atoms.•Ferromagnetism induced by Nb vacancy comes from 2py and 2pz states of nearest O atoms.•Sr2AlNbO6Sr2AlNbO6 with O vacancy is energetically more favorable than with others.Based on first-principles calculation the change of structural, energetic, magnetic and electronic properties of double perovskite oxide Sr2AlNbO6 is investigated by introducing intrinsic vacancies. Calculated results show that although both Al and Nb vacancies could induce ferromagnetism the nature of induced ferromagnetism is different. Ferromagnetism driven by Al vacancies originates from the remarkably spin-polarized 2px state of nearest O atoms, whereas that induced by Nb vacancy mainly comes from the partially filled spin-polarized 2py and 2pz states of nearest O atoms. Sr2AlNbO6 with O vacancy is nonmagnetic but energetically more favorable than that with the other three vacancies.

•The dielectric properties of FeNbO4 exhibits three thermally activated relaxations.•Low-T relaxation was caused by the hopping motion of the self-trapped electrons.•Middle-T relaxation is related to the electrons hopping between Fe2+ and Fe3+ ions.•High-T relaxation was argued to be a Maxwell–Wagner relaxation.The dielectric properties of FeNbO4 ceramics were systematically investigated in the frequency range from 100 Hz to 5 MHz and temperature from 75 to 300 K. It is observed that the sample exhibits colossal dielectric behavior and three dielectric relaxations. Both the low- and middle-temperature relaxations were found to be bulk effect related to localized carriers hopping. It is revealed that the low temperature relaxation is caused by the hopping motion of the self-trapped electrons and the middle temperature relaxation is related to the electrons hopping between Fe2+ and Fe3+ ions. By means of complex impedance analysis the high-temperature relaxation was argued to originate from Maxwell–Wagner relaxation due to grain boundary response.

•Na0.5K0.5NbO3 ceramic samples were prepared via the solid-state reaction route.•Dielectric behavior of the sample was studied by electric modulus spectroscopy.•Two oxygen-vacancy-related relaxations were observed in Na0.5K0.5NbO3.Na0.5K0.5NbO3 ceramic samples were prepared via the solid-state reaction route. The low-frequency (20–107 Hz) dielectric properties were investigated in the temperature range from room temperature to 1073 K. Two relaxations were observed in the spectra of electric modulus. Relaxation 1 occurs in the orthorhombic phase, which was ascribed to be related to the oxygen-vacancy clusters. Relaxation 2 appears in the tetragonal and cubic phases. It behaves as a Maxwell–Wagner-type and polaron-type relaxation in the tetragonal and cubic phase, respectively.

Highlights•Both Al and Ta vacancies could induce ferromagnetism in Sr2AlTaO6.•Ferromagnetism driven by Al vacancy originates from the 2px state of nearest O atoms.•Ferromagnetism induced by Ta vacancy comes from 2py and 2pz states of nearest O atoms.•Sr2AlTaO6 with O vacancy is energetically more favorable than with others.The changes of structural, energetic, magnetic and electronic properties in double perovskite oxide Sr2AlTaO6 due to introducing intrinsic vacancies are investigated by first-principles calculation. Calculated results show that although both Al and Ta vacancies could induce ferromagnetism the nature of induced ferromagnetism is different. Ferromagnetism driven by Al vacancy originates from the remarkably spin-polarized 2px state of nearest O atoms, whereas that induced by Ta vacancy mainly comes from the partially filled spin-polarized 2py and 2pz states of nearest O atoms. Sr2AlTaO6 with O vacancy is nonmagnetic but energetically more favorable than that with the other three vacancies.

•Both Debye-like relaxation and relaxor-like anomaly were observed in CaF2.•Raman and DSC results revealed that the defects in CaF2 are VF, F′iF′i, and oxygen ions.•The Debye-like behavior was ascribed to the mobility of the fluorine vacancies.•The anomaly stems from the relaxation associated with the dipolar complex of O″−VF.The dielectric properties of CaF2 single crystals were investigated in the temperature range from room temperature to 773 K and the frequency range of 50 Hz–10 MHz. A Debey-like relaxation and a relaxor-like dielectric anomaly were observed. Raman spectrum and the differential scanning calorimeter measurement revealed the coexistence of native defects of fluorine vacancies (VF) and interstitial fluorine ions (F′iF′i) and external defect of oxygen ions. Impedance analysis showed that the Debey-like relaxation results from the mobility of VF, while the relaxor-like behavior is associated with the relaxation caused by complexes of O″−VF.

We reported the dielectric properties of CaCu3Ti4O12 in the temperature range from room temperature to 800°C and the frequency range from 20 Hz to 10 MHz. Apart from the widely reported dielectric anomaly occurring around 200°C, three additional dielectric anomalies were found. The new anomalies are very sensitive to electrode sintering conditions and annealing atmospheres, indicating that they are dependent not only on the electrode-sample contact but also on oxygen vacancies.

We herein discuss the equivalent circuits for polaronic relaxation based on the results of the low-temperature dielectric properties of LaNi3/4Mo1/4O3. The ceramic samples were prepared via solid-state reaction route. The dielectric properties were investigated in the temperature range from 103 K to 330 K and the frequency range from 20 Hz to 10 MHz. Our results showed that the Debye-like relaxation found in the sample was related to be a polaronic relaxation caused by localized carriers. At low enough temperatures below 103 K, the carriers were strictly confined and the equivalent circuit for impedance spectra was an ideal capacitor. At the temperatures around room temperature, the carriers can hop between spatially fluctuating lattice potentials, the circuit of R − CPE (R = resistance, CPE = constant phase element) was found to be the better model to describe the impedance data.

Cobalt-containing perovskite, PrNi0.6Co0.4O3 (PNC) has been investigated as a possible candidate for cathode material for intermediate temperature solid oxide fuel cells. It is found that the maximum and minimum electrical conductivity of PNC are 1580 S cm−1 at 50 °C and 1031 S cm−1 at 1000 °C, respectively. The thermal expansion coefficient (TEC) of the PNC is 14.21 × 10−6 K−1 at 700 °C. The TEC of the PNC–50 wt.% Ce0.8Sm0.2O1.9 (PNC–50SDC) composite cathode is 13.49 × 10−6 K−1 at 700 °C, which is much more matching with the other components within the cell. The cathodic polarization of the single-phase PNC and composite cathodes with SDC shows that a weight ratio between PNC and SDC of 50:50 yields the lowest area specific resistance of 0.097 Ω cm2 at 600 °C and 0.031 Ω cm2 at 700 °C. The maximum power density of the PNC–50SDC cathode in an anode-supported SOFC is 1.09 W cm−2 at 700 °C.Highlights► The electrical conductivity of the PNC is 1031 S cm−1 at 1000 °C. ► The TEC of the PNC–50SDC cathode is 13.49 × 10−6 K−1 at 700 °C. ► The ASR of PNC–50SDC yields the lowest value of 0.031 Ω cm2 at 700 °C. ► The maximum power density of the PNC–50SDC cathode is 1.09 W cm−2 at 700 °C.

The perovskite LaFeO3 ceramic samples were synthesized by the solid-state reaction. The dielectric properties of LaFeO3 were investigated as functions of frequency (102–106 Hz) and temperature (80–315 K). The sample exhibits colossal dielectric behavior similar to that found in CaCu3Ti4O12. This behavior was linked with a Debye-like relaxation with activation energy of 0.237 eV. With the analysis based on Debye's theory and a series of Arrhenius relations, the relaxation was argued to be associated with the hopping motions of charge carriers between Fe2+ and Fe3+, and the relaxation in LaFeO3 in the investigated temperature range was ascribed to be a polaronic relaxation.Highlights► Colossal dielectric behavior similar to that found in CaCu3Ti4O12 was reported in LaFeO3 ceramics. ► This behavior was found to be related to polaronic relaxation due to electrons hopping between Fe2+ and Fe3+. ► LaFeO3 ceramic samples were synthesized via the solid-state reaction.

In this work, the dielectric properties of La0.8Bi0.2Fe0.7Mn0.3O3 ceramics have been investigated in a temperature range of 76–320 K and a frequency range of 300 Hz–10 MHz. Two thermally activated dielectric relaxations were observed with the activation energy around 0.283 ± 0.007 eV for the low-temperature relaxation and 0.268 ± 0.007 eV for the high-temperature relaxation. Annealing in N2 and O2 can destroy and create the high-temperature relaxation, respectively. But the treatments have no significant influence on the low-temperature relaxation. The low-temperature relaxation was found to be bulk effect related to the dipolar effect due to the hopping polarons, and the high-temperature relaxation was associated with the Maxwell–Wagner relaxation due to surface-layer effect caused by hopping polarons blocked and trapped at the surfaces of the sample.Highlights► Dielectric properties of La0.8Bi0.2Fe0.7Mn0.3O3 ceramics have been investigated. ► Two thermally activated dielectric relaxations were observed. ► The low-temperature relaxation was found to be bulk effect. ► The high-temperature relaxation was associated with the Maxwell–Wagner relaxation. ► These relaxations were confirmed to be closely linked with the localized polarons.

Double-perovskite Ca2CoNbO6 (CCNO) ceramics were prepared via the solid-state reaction route. Their dielectric properties were investigated as a function of temperature (between 100 and 330 K) in the frequency range from 40 Hz to 10 MHz. Two thermally activated dielectric relaxations were observed with the activation energy around 0.13 eV for the low-temperature relaxation and 0.37 eV for the high-temperature relaxation. Annealing in O2 and N2 can remarkably change the dielectric constant, background, relaxation peak intensity and position, etc. These results can be well explained based on the fact that both oxygen and cobalt vacancies coexist in the sample. The low-temperature relaxation was found to be related to the dipolar effect due to the hopping holes, and the high-temperature relaxation was associated with the defect relaxation caused by oxygen and cobalt vacancies.

In the present work, we performed detailed investigation on the relationship between the dielectric properties and the conductivity of Ba2FeNbO6. Our results revealed that (1) the colossal dielectric behavior of the sample can be well understood based on the framework of universal dielectric response, (2) the observed relaxation shows a distinct deviation from the Arrhenius behavior, and (3) the peak intensity of dielectric loss can be well expressed by a relation similar to the Fermi–Dirac distribution function rather than a thermally activation relation. These are the typical features for the hopping motions of polaronic carriers demonstrating that the dielectric properties and the conductivity of Ba2FeNbO6 are closely linked.

LaNi0.6Fe0.4O3 (LNF), LNF–Sm0.2Ce0.8O1.9 (SDC), and LNF–SDC–Ag cathodes on SDC electrolytes were investigated at intermediate temperatures using AC impedance spectroscopy. Results show that adding 50 wt.% SDC into LNF yields a significant low area specific resistance (ASR) which was found to be 0.92 Ω cm2 at 700 °C. Infiltrating 0.3 mg/cm2 Ag into LNF-50 wt.% SDC can improve the electronic conductivity and oxygen exchange reaction activity, and thereby remarkably decrease the ASRs. The ASR value of the LNF–SDC–Ag cathode is as low as 0.18 Ω cm2 at 700 °C, and 0.46 Ω cm2 at 650 °C. The long-term test shows that the LNF–SDC–Ag cathode may be a promising candidate for solid oxide fuel cells operating at temperatures lower than 650 °C.Highlights►Adding 50 wt.% SDC into LNF yields a significant low area specific resistance (ASR). ► Infiltrating Ag into LNF-50 wt.% SDC can improve oxygen exchange reaction activity. ► The ASR value of the LNF–SDC–Ag cathode is as low as 0.46 Ω cm2 at 650 °C.

SrLaAlO4 ceramic samples were prepared via solid state reaction method. The low-frequency (20–107 Hz) dielectric properties were investigated in the temperature range from room temperature to 700 °C. It was found that SrLaAlO4 shows intrinsic dielectric behavior with a dielectric constant of 13 in the temperature range below ~300 °C. In the temperature range from 300 °C to 560 °C, the bulk dielectric contribution due to oxygen-vacancy-related polarons dominates the dielectric properties of the samples. However, the dielectric properties are controlled by sample/electrode contacts when the temperature is risen to above 560 °C. Our results indicate that the bulk effect instead of interfacial effect is the main contribution to dielectric loss in the lower temperature range.

Hollow metal chalcogenides have attracted increasing attention in recent years owing to their widespread applications. However, to the best of our knowledge, the effective synthesis of a uniform Fe3S4 hollow nanostructure for fundamental research and practical application has not been reported to date. In this paper, a facile method for preparing nanostructured Fe3S4 with controlled hollow spheres was developed. The as-prepared Fe3S4 shows ferromagnetic characteristic and porous nature. Their Li ion storage and water treatment performances are further tested. Such mesoporous hollow spheres exhibit a highly reversible capacity of 750 mA h g−1 over 100 cycles at a current density of 0.2 A g−1. In addition, when used as an adsorbent, the Fe3S4 exhibited high adsorption capability and the adsorption isotherms are subject to the Freundlich equation. This work not only presents a facile strategy for the synthesis of novel Fe3S4 hollow spheres but also supplies a promising advanced material for lithium-ion batteries and water treatment.