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Titanium dioxide (TiO2) has been acknowledged as one of the efficient photocatalysts in the UV region. To extend the photo-absorption region toward visible lights, the TiO2 nanowires enclosed with carbon shells (TiO2@carbon core-shell nanowires) were synthesized by a chemical vapor deposition technique at various temperatures from 650 to 950 °C. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that TiO2 cores and carbon shells are rutile and graphitic structures, respectively. From Raman spectra, the peak intensity of the Eg mode was observed to be redshifted with elevated growth temperatures due to the increase in oxygen vacancies in the TiO2@carbon core-shell nanowires. From X-ray photoelectron spectroscopy (XPS) results, the oxygen vacancies were strongly related to the Ti3+ ions. The UV–visible spectroscopic studies show a possible decrease in photocatalytic energy from 3.1 to 2.7 eV for the TiO2@carbon core-shell nanowires, indicating that the light absorption was enhanced in the visible-light region. The optical absorbance results confirmed the presence of the mid-gap states due to the oxygen vacancies, which are responsible for the visible-light absorption. The photocatalytic activity of the TiO2@carbon core-shell nanowires studied by methylene blue (MB) dye degradation is effective under visible lights.

Two series of samarium co-doped in 10 mol% Gd doped ceria Ce0.90Gd0.1O1.95(GDC10) formulated as Ce0.9-xSmxGd0.1O2-δ(CS) and Ce0.9Gd0.1-xSmxO2-δ(GS) (x = 0.0, 0.03, 0.05 0.10) were synthesized by glycine nitrate auto combustion method. The structural effects of Sm substitution in the GDC10 solid solution have been studied by X-ray diffraction (XRD) and Raman spectroscopy techniques. An increased lattice constant (5.407 A to 5.414 A) with decreasing crystallite size (28.6 nm 22.5 nm) was observed in both the Ce substituted by Sm (CS) and Gd substituted by Sm (GS) in GDC10 crystal system. The highest oxygen vacancy concentration ( V O ⋅ ⋅ = 2.65 × 1021 cm−3) was found for 10 mol % Sm and 10 mol % Gd doped ceria (Ce0.8 Sm0.1Gd0.1O1.90) composition (CS10) evaluated by spatial correlation model from Raman spectroscopy. The microhardness of the sintered pellets was investigated by Vickers hardness measurement. The highest fracture toughness was found to be 1.85 ± 0.27 MPa m1/2 for Ce substituted by 3 mol% Sm composition (CS3) among the overall compositions. The surface morphology and elemental composition of the CS and GS compositions were analyzed by FESEM. The morphology and composition of optimized electrolyte (CS10) was further analyzed by HRTEM and XPS respectively. AC impedance spectroscopy revealed that CS10 composition has an improved ionic conductivity (σ800 = 0.147 × 10−3 S‧cm−1) with significantly reduced activation energy (0.85 eV) in the temperature range of 673–1073 K under air atmosphere. A mechanism for conductivity enhancement by oxygen vacancy for CS compositions has been proposed. The effect of Sm as a secondary co-dopant in the GDC10 electrolyte was studied in detail to establish a candidate electrolyte material for operating solid oxide fuel cells in the intermediate temperature range (673–1073 K).

In this work we propose a study to determine the structure of Fe and Co doped TiO2 by using the Fe K-edge, Co K-edge and Ti K- edge X-ray absorption near edge spectroscopy. The detailed analysis of Fe and Co-doped TiO2 before and after Methylene blue (MB) treatment was examined under the irradiation of 35 W xenon arc lamp for 3 h. The materials treated with MB were studied by X-ray absorption spectroscopy, EPR and FT-IR which revealed that the oxidation state of Co2+ was photo-oxidized to Co3+ and Fe3+ was photo-reduced to Fe2+ or less. Thermodynamic, kinetic properties were studied at different reaction temperature and the activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) of activation were calculated for the reaction. The activation energy has been found for TiO2, Fe TiO2 and Co TiO2 as 24.771, 11.413 and 15.801 kJ mol−1 respectively. The structure, morphology and optical properties were studied by XRD, UV-diffuse reflectance spectra, FESEM, TEM and PL. Moreover, electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER) activity on TiO2, Fe TiO2 and Co TiO2 in 1 M of H2SO4 electrolyte, with a scan rate of 50 mV s−1 and the as-prepared photocatalysts could act as the promising electrode materials for water splitting.

In this study, the crystal structure, thermal, oxygen transport, electrical conductivity and electrochemical properties of the perovskite NdBa0.5Sr0.5Co2O5+δ (NBSC55) are investigated. In the temperature range of 250 °C–350 °C, the weight loss upon heating was due to a partial loss of lattice oxygen and along with a reduction of Co4+ to Co3+. The tend of weight-loss slows down as temperature increased above 350 °C indicating a reduction of Co3+ to Co2+ during this stage. The oxygen migration is dominated by surface exchange process at high temperature range (650-800 °C); however, the bulk diffusion process prevails at low temperature range (500–600 °C). For long-term testing, the polarization resistance of NBSC55 increases gradually form 3.13 Ω cm2 for 2 h to 3.34 Ω cm2 for 96 h at 600 °C and an increasing-rate for polarization resistance is around 0.22% h−1. The power density of the single cell with NBSC55 cathode reached 341 mW cm−2 at 800 °C.

Herein, we synthesize a Cu-cuprous/cupric oxide-based family of catalysts via simple hydrothermal technique, and investigate the effect of copper oxide phases on the application of interest. These catalysts are applied towards dual application namely 4-nitrophenol (4-NP) conversion and electrochemical hydrogen evolution reaction (HER). Due to the difference in mechanism of these both applications, we pick up two best catalysts for either application. We explore these differences through intensive characterizations such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction of hydrogen (H2-TPR) analysis. XRD reveals the presence of varying copper oxide phases across all the synthesized catalysts. XPS discovers the disparities between catalysts annealed at various temperatures. Reducibility of catalysts is studied via H2-TPR since they can disclose phase conversions taking place in the material thereby directly affecting the application. Cu-Cu2O (150℃) could convert 98.6 % of 50 ppm 4-NP into 4-aminophenol (4-AP) with recycle tests up to 10 cycles yielding conversion values between 96.3–98.9% which are high enough for any catalyst to reach its maximum potential. CuO-Cu2O (300℃) exhibits best HER activity with the least onset potential of -0.28 V vs. RHE at 1 mA cm-2 possessing a maximum current density of 366 mA cm-2.

The plasmonic metal-induced Bi2WO6/TiO2 ternary composite with unique electronic and structural properties was synthesized via a hydrothermal and chemical reduction route for sustainable energy and environmental remediation. The obtained Bi2WO6/TiO2-Ag (BWTA) exhibited a tremendous catalytic activity for Rhodamine B photodegradation (0.947 × 10-2 min−1) than those of sole TiO2 and Bi2WO6 specimens. The radical trapping experiment discloses that superoxide .O2− and holes (h+) are the cardinal active species in the photocatalytic system. Further, recycling experiment was conducted to elucidate the stability of the photocatalyst. BWTA2.0 was able to produce 2.1330 mA/cm2 of current density for oxygen evolution reaction and −1.5003 mA/cm2 for hydrogen evolution reaction, which is much higher than those of other specimens. Besides, electrochemical detection of dopamine (DA) was performed through cyclic voltammetry; results showed that the ternary composite had better electrocatalytic activity for DA detection owing to the synergistic effects of noble metal incorporation into the semiconductor. Also, the antibacterial potential of the specimens was explored against Escherichia coli through the well-diffusion method. In terms of experimental results, a possible mechanism of ternary composite is thoroughly elucidated. Thus, this work validates that, plasmonic induced ternary composite has a great prospect for photocatalytic, electrochemical, sensing, and antibacterial applications.

In this study, the electrochemical impedance spectroscopy (EIS) technique was used to investigate the electrochemical behavior of the interface between the Mo electrode and the Cu-In-Ga-Se electrolyte. In this electrodeposition system, the main parameters include (1) various deposition times, and (2) the effect of In 3+ concentration on the diffusion processes, electrical double layer, charge transfer resistance, and Warburg impedance. Experimental results revealed that the electrochemical kinetic behavior of CIGS thin film is strongly influenced by (1) the electrical double layer existing between the substrate, and (2) the electrolyte with different concentrations of In 3+ . With an increase in the electrodeposition time, the kinetic behavior of this electrodeposition system was gradually dominated by the diffusion process rather than charge transfer process.

Ciprofloxacin (CIP) is a fluoroquinolone family antibiotic pollutant. CIP existence in water environment has been rising very fast in day-to-day life and subsequently, it gives enormous health issues for humans because of its potent biological activity. To encounter this, current researchers are focusing on the development of highly efficient visible light semiconductor nanocomposites with potential photocatalytic activity. In the present work, we have successfully synthesized highly efficient zinc-aluminum layered double hydroxides with graphitic carbon nitride (ZALDH/CN) composites via a simple microwave irradiation method first time for the degradation of CIP under visible light. The fabricated materials are subsequently characterized by various spectroscopic techniques. UV–Vis DRS, TRFL, XRD, FT-IR, BET, FE-SEM, TEM, and XPS for optical, crystal structure, morphological, and elemental analysis. The main reactive intermediates which are formed during the photocatalytic degradation process were analyzed by LC-MS analysis. It is worth to note that, the optimized ZALDH/CN-10 composite showed the highest photo-degradation rate constant of 1.22 × 10−2 min−1 with 84.10% degradation is higher than bare CN and ZALDH photocatalysts. Based on the electron-hole pair trapping experiment results, possible CIP photo-degradation mechanism was also explained in the present study. With all results, this work demonstrates the ZALDH/CN composite materials showed a high synergistic effect with more specific surface area. Highest specific surface area leads to enhanced visible light adsorption capacity. Subsequently improved number of catalytically active sites. Furthermore, as compared with pure materials, composites of ZALDH/CN are having low electron-hole pair recombination. Consequently, the composites ZALDH/CN showed superior photocatalytic activity for antibiotic pollutant CIP degradation under visible-light illumination.

Noble metals are very well known for their surface plasmon resonance property that facilitate of better light absorption in the visible region particularly for gold and silver. Nevertheless, unlike semiconductors, noble metals are commonly considered lacking the ability to accelerate reactions by way of photogenerated electron-hole pairs due to their continuous energy band structure. Here, we report a one dimensional (1D) AgNWs combined with BiOCl/BiVO4 photocatalysts have been synthesized at room temperature. BiOCl/BiVO4 photocatalysts have been synthesized in the presence of deep eutectic solvents (DESs), also known as deep eutectic ionic liquids (DEILs).The synthesized product was characterized using various techniques. Surface morphology was analyzed using SEM and TEM, which shows a sheet like shaped structure from sol–gel method. The structural, optical properties were investigated by X-ray diffraction (XRD), UV–vis spectrophotometer, and Photoluminescence (PL) spectroscopy measurements. The BiOCl/BiVO4@AgNWs shows a better degradation of methylene blue (MB) and rhodamine B (RhB) than pure BiVO4 illuminated under a Xe arc lamp with 35 W and color temperature of 6000 K. Also, the significant enhancement of visible-light-driven photocatalytic activity should be ascribed to the formation of the BiOCl/BiVO4 heterojunction, which can result in the high separation and transfer efficiency of photogenerated charge carriers. It was verified by electrochemical impedance spectra (EIS) and linear sweep voltammetry (LSV).

SmBa 0.5 Sr 0.5 Co 2 O 5+δ (SBSC55) impregnated with nano-sized Ce 0.8 Sm 0.2 O 1.9 (SDC) powder has been investigated as a candidate cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The cathode chemical compatibility with electrolyte, thermal expansion behavior, and electrochemical performance are investigated. For compatibility, a good chemical compatibility between SBSC55 and SDC electrolyte is still kept at 1100 °C in air. For thermal dilation curve, it could be divided into two regions, one is the low temperature region (100–265 °C); the other is the high temperature region (265–850 °C). In the low temperature region (100–265 °C), a TEC value is about 17.0 × 10 −6 K −1 and an increase in slope in the higher temperatures region (265–800 °C), in which a TEC value is around 21.1 × 10 −6 K −1 . There is an inflection region ranged from 225 to 330 °C in the curve of d ( δL / L )/ dT vs. temperature. The peak inflection point located about 265 °C is associated to the initial temperature for the loss of lattice oxygen and the formation of oxygen vacancies. For electrochemical properties, the polarization resistances (R p ) significantly reduced from 4.17 Ω cm 2 of pure SBSC55 to 1.28 Ω cm 2 of 0.65 mg cm −2 of SDC-impregnated SBSC55 at 600 °C. The single cell performance of SBSC55∣SDC∣Ni-SDC loaded with 0.65 mg cm −2 SDC exhibited the optimum power density of 823 mW cm −2 at operating temperature of 800 °C. Based on above-mentioned properties, SBSC55 impregnated with an appropriate SDC is a potential cathode for IT-SOFCs.

Ag nanoparticles with different weight percentage loaded on Ni-Cu-Zn ferrite@SiO 2 @TiO 2 composite were successfully prepared via sol-gel method. The effect of deposited amount of Ag nanoparticles on structural, magnetic and photocatalytic properties of the composite was investigated. XPS characterization confirmed that Ag nanoparticles deposited on the surface of Ni-Cu-Zn ferrite@SiO 2 @TiO 2 composite. Particle size and shape of magnetic recyclable photocatalysts were observed using TEM, showing a core-shell structure with an average particle size of 20 nm of Ag. Based on room temperature magnetic hysteresis curves, as 0.4 wt% Ag immobilized on Ni-Cu-Zn ferrite@SiO 2 @TiO 2 composite revealed the maximum saturation magnetization of 39.9 emu/g. Photocatalytic degradation of Ni-Cu-Zn ferrite@SiO 2 @TiO 2 @Ag was carried out in methylene blue (MB) solutions illuminated under a 35-W Xe arc lamp and color temperature of 6000 K. The results revealed that 83.9% of MB was photodegraded for 0.4 wt% of Ag-loaded Ni-Cu-Zn ferrite@SiO 2 @TiO 2 . Moreover, it can be easily separated and recycled without significant loss of photocatalytic activity after being used five times. Compared to the conventional photocatalysts, the magnetic core–shell photocatalyst is suitable for large scale applications in industrial wastewater system.

Oxygen transportation properties of SmBa0.5Sr0.5Co2O5+δ (SBSC55) layered perovskite has been investigated as a potential cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This research includes the following items: (1) structural characteristics, thermogravimetric behavior, oxygen permeation, chemical bulk diffusion coefficient (Dchem), and (2) the electrochemical performance of long-term testing carried out to evaluate its electrochemical stability. The Dchem values for SBSC55 cathode are 2.6 × 10−6, 9.1 × 10−6 and 1.8 × 10−5 cm2 s−1 at 500 °C, 600 °C, and 700 °C, respectively. The oxygen permeation flux for SBSC55 membrane with 1.0 mm thickness increased from 0.143 mL min−1 cm−2 at 500 °C to 0.406 mL min−1 cm−2 at 800 °C under synthetic air at a flow rate of 50 mL min−1, helium at a rate of 25 mL min−1. The activation energies of oxygen permeation for the high temperature region (700–800 °C) and low temperature region (500–650 °C) are 23.67 and 6.96 kJ mol−1, respectively. It suggested that oxygen diffusion for high temperature range is surface exchange process, low temperature range is bulk diffusion process. The long-term test of cathodic polarization resistance for SBSC55∣SDC∣SSBSC55 half-cell at 600 °C during 96 h has been carried out with an increase rate of 0.30% h−1. Based on the impedance spectra with various oxygen partial pressure results, the rate-limiting process of ORR is determined that the oxygen ion transfer from triple-phase boundary (TPB) and/or two-phase boundary (2PB) sites of cathode is major with the minority of charger transfer reaction.

Herein, we synthesized a bi-function hybrid material and investigated the dynamic nature of synergy between the individual components of the hybrid and its application aspects in detail. The diverse nature of 2D-ternary hybrid could be exploited as a photocatalyst as well as an electrochemical sensor. Plate-like Bi2WO6 was hybridized with mesh-like g-C3N4 structure and subsequently rGO being loaded into it via simple hydrothermal route. Based on room temperature EPR spectra, we could interpret the inactivity of Bi2WO6 and significant activity of 2D-ternary hybrid. The hybrids were evaluated based on the photocatalytic degradation of antibiotic ciprofloxacin (CIP). Bi2WO6/g-C3N4/rGO hybrid yielded 90% degradation in 110 min while CIP photolysis only yield 4.3%. Mechanism of photocatalytic degradation was investigated via scavenger experiments which gave away the reactive radicals responsible. To investigate the effect of carrier lifetime on photocatalytic ability, time resolved fluorescence life (TRFL) experiments were performed. The relationship between reducibility and enhanced photocatalytic ability of the materials was studied via hydrogen temperature-programmed reduction (H2-TPR) measurement. Furthermore, for elaborating application of the synthesized 2D structured ternary hybrid, its electrochemical ability towards 4-nitrophenol (4-NP) sensing was also studied. An electrochemical sensitive electrode was fabricated to evaluate sensing properties towards 4-NP. To study the electrode kinetics on 4-NP solution, varying scan rate was used via the cyclic voltammetry (CV) analysis. The fabricated BCN-200/rGO electrode delivered promising sensing properties with excellent sensitivity of 12.86 μA.μM−1.cm−2 in range of 0.2–100 μM. Hence, the synthesized 2D-ternary hybrid possesses great potential applications in the field of photocatalysis as well as electrochemical sensor.

Metal-organic frameworks (MOFs) are evolving as emerging materials for application in supercapacitors on account of their inherent porous characteristics, which can be suitably controlled with molecular engineering. This allows suitable attributes to MOFs such as multiple dimensionalities, high surface area and additional aspect ratio compared to traditional materials. Secondary building units (SBUs) are the milestones that allow immense structural diversity, thermodynamic stability, and mechanical/architectural stability to demonstrate materials on-demand with predetermined topologies in the synthesis of MOFs through stronger bonding between the constituent metals and organic linkers. Despite these advancements, the usage of pristine MOFs is lagging in the area of supercapacitor, majorly due to their insulating nature. As smart avenues, hybridization of MOFs or using MOFs as templates for deriving metal oxide, carbon or hydroxides etc., are being proved as hugely successful. This review is directed towards the utilization of MOFs, specifically three-dimensional MOFs as a platform for utilization in supercapacitor. Extensive discussion is developed on divergent methods related to the synthesis of MOFs, their performance in supercapacitor application and various strategies adopted to enhance their functionality. Finally, the future prospective and possible research proceedings in this field are described briefly.

Fabrication of an efficient, stable, and versatile photocatalysts for the energy and environment remediation applications is an urgent task for the current researchers. In this work, we have successfully synthesized a versatile hybrid photocatalysts, i.e.; CdMoO4/g-C3N4 (CMO/CN) by a facile and simple one-pot in-situ hydrothermal method. Here CdMoO4 (CMO) microspheres were deposited on the g-C3N4 (CN) sheets. Fabricated CN, CMO, and CMO/CN composite photocatalysts were analyzed with various characterization techniques like UV–visible diffuse reflectance spectra (UV–Vis DRS), photoluminescence spectroscopy (PL), time-resolved fluorescence lifetime (TRFL), electrochemical impedance spectroscopy (EIS), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy–energy-dispersive X-ray analysis (SEM-EDX), transmission electron microscope (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The results reveal that the formation of a strong heterojunction between two semiconductors leads to the formation of active photocatalyst. Furthermore, as-synthesized materials were tested for the photoelectrocatalytic (PEC) oxygen evolution reactions (OERs) in acidic medium, and photocatalytic (PC) degradation of methylene blue (MB) under light irradiation. Among all tested samples, CMO/CN-10 has shown the highest current density 52.74 mA cm−2 at 1.95 V with lowest over potential of 0.70 mV on glassy carbon electrode for OER in acidic medium under the light irradiation. The PC degradation rate constant of CMO/CN-10 composite in MB solution is k = 2.0 × 10−2 min−1, whereas for the pure CMO and CN degradation rate constant is k = 5.7 × 10−3 min−1 and k = 1.2 × 10−2 min−1, respectively. This enhancement in PEC and PC properties is due to the fast migration of photo-induced electrons in the case of CMO/CN-10 nanocomposite. Trapping experiment results reveal the major reactive species for PC degradation of MB is •OH (hydroxyl radicals) and h+ (holes), respectively, and suitable PC reaction mechanism also proposed for CMO/CN-10 composites. Based on the above remarkable results, it would be a potential nanocomposite for the PEC oxygen evolution and PC degradation of MB under light illumination.

The development of perovskite-based materials with a narrow bandgap for oxygen evolution reactions (OER) and wastewater treatment have much attention in recent years. Herein, a narrow bandgap of Ca-doped BiFeO3 (BCFO) is synthesized by a simple auto combustion method. To create oxygen vacancies by doping Ca2+ the place of Bi3+, the amount of Fe3+ valence state is changed as well. 0.15% of Ca doped BiFeO3 (BCFO-15) indicate a high content of Fe4+ state with a conduction band and valence band located at 0.615 V and 2.46 V vs. NHE, respectively. The electrochemical OER of BCFO-15 observed a lower onset potential of 2.13 V vs. RHE, in acidic with a current density of 25.64 mA cm−2. In alkaline electrolyte, onset potential was observed at 2.10 V vs. RHE, with a current density of 65.87 mA cm−2. Furthermore, the photocatalytic performance of the perovskites in aqueous solution was demonstrated through photocatalytic reduction of Cr(VI) as a model pollutant, resulting in an 89.92% reduction of 50 ppm of Cr(VI) in 210 min under the irradiation of a 35 W Xe arc lamp. These findings suggest that simple divalent doping of Ca into pure BiFeO3 results in excellent photocatalytic and electrocatalytic perovskites.

The purpose of this project is investigate the oxidation reaction of 2,3,6-Trimethylphenol (TMP) green chemistry process design for magnetic nano-catalysts by microwave-induced combustion process. Design chemical syntheses to prevent waste, in order to reduce the raw materials cost, to improve the performance for 2,4,6-Trimethylbenzoquinone(TMBQ) production, and by the way to solve the environmental pollution problem from the scraps. The whole project will be completed that, Preparation of magnetic Cu–Zn ferrite nano-catalysts (Cu1-XZnXFe2O4) by microwave-induced combustion process, the characterized of catalysts and micro-structure was carried out. The kinetics and mechanism of two phase medium are also studied in Cu–Zn ferrite/TiO2 magnetic nano-catalysts.

The doped lanthanum chromite (La 0.8 Ca 0.2 )(Cr 0.9− x Co 0.1 Mn x )O 3 ( x =0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV–visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46 eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).

The effects of Sr doping on the Ba-site of SmBaCo2O5+δ in term of structure characteristics, thermal expansion coefficients (TECs), electrical properties and electrochemical performance have been investigated as cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The TECs of SBSC-based cathodes are calculated from 19.8 − 20.5 × 10−6 K−1 in the temperature range of 100–800 °C, and the TEC values decrease with increasing Sr content. The oxygen content and the average oxidation state of cobalt increase with increasing Sr content determined by the X-ray photoelectron spectroscopy (XPS) and Thermogravimetry analysis (TGA) results. At a given temperature, the electrical conductivity values are in the order as follows: SBSC55 > SBSC73 > SBSC91. This behavior might be due to the increase in electronic hole. The electrical conductivities of SBSC55 at 600 °C are distributed in the range of 660 S/cm of p(O2) = 0.01 atm to 1168 S/cm of p(O2) = 0.21 atm, indicating that the cathode can endure reducing atmosphere. SBSC55 with high electrical conductivity in p(O2) = 0.01 atm is ascribed to SBSC55 with stable double-perovskite structure at such low oxygen partial pressure. The SBSC55 cathode showed the highest power density of 304 mW/cm2 at operating temperature of 700 °C. Based on the electrochemical properties, SBSC55 is a potential cathode for IT-SOFCs.

The aim of the work is to study the effects of oxygen vacancy and surface hydroxyl group density on the photocatalytic activity of Fe3+-doped TiO2, and to investigate how the titanium dioxide doped with different levels of the Fe3+ influenced their physical and chemical characterizations. The photocatalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), electron spin resonance (ESR), X-ray photoelectron spectroscope (XPS) and Fourier transform infrared (FTIR) spectra. The results revealed that adsorbed hydroxyl group density significantly influenced the photocatalytic activity, and a small amount of Fe3+ can act as a photo-generated hole and a photo-generated electron trap and inhibit the electron–hole recombination. The 0.10%-Fe3+-TiO2 with the highest surface hydroxyl group density revealed the maximum rate constant of 0.716 and the optimal photocatalytic degradation of MB. As Fe3+ doping levels are larger than 0.10%, the cluster of Fe Ti ′ – V ¨ O – Fe Ti ′ generated gradually. This implied that an excessive amount of Fe3+ doped into TiO2 is detrimental to the photocatalytic activity due to the formation of Fe Ti ′ – V ¨ O – Fe Ti ′ clusters and enhances the recombination of photogenerated electrons and holes.

The chemical stability of potassium substituted for A-site of SrCe 0.95 Y 0.05 O 3 specimens was examined under CO 2 atmosphere treated at 600 °C and further analyzed by X-ray diffractometer to see their CO 2 -resisted capabilities. According to thermodynamic data, the Gibbs free energy of CeO 2 was lower than that of SrCO 3 at the temperature of 600 °C. Thus the formation of CeO 2 might be faster than that of SrCO 3 in SrCeO 3− based materials under CO 2 atmosphere. Unfortunately, the chemical stability of SrCe 0.95 Y 0.05 O 3 materials in CO 2 atmosphere was reduced with increasing potassium-substituted amount. The microstructures of Sr 1− x K x Ce 0.95 Y 0.05 O 3 sintered specimens were identified using field emission scanning electron microscope. The conductivity in moisture H 2 atmosphere (RH 30%) was increased with increasing potassium-substituted concentration. The conductivity reached a maximum of 0.0081 Scm -1 at 900 °C for Sr 0.95 K 0.05 Ce 0.95 Y 0.05 O 3 sintered specimens in moisture H 2 atmosphere (RH 30%). Potassium substituted for A-site of SrCe 0.95 Y 0.05 O 3 could improve the conductivity but not CO 2 -resisted capability.

In this work, the chemical bulk diffusion coefficient ( D chem ) of SmBa 0.6 Sr 0.4 Co 2 O 5+ δ was determined by an electrical conductivity relaxation (ECR) method. The equation of D chem as a function of temperature in the range of 500–700 °C exhibits as follows: D chem = 1.77×10 −5 (−68.039 (kJ mol −1 )/ RT ) (m 2 s −1 ) Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600–850 °C to determine the cathode polarization resistance ( R p ). The area specific resistances (ASR) of SmBa 0.6 Sr 0.4 Co 2 O 5+ δ -Ce 0.8 Sm 0.2 O 1.9 (70:30 in wt%) composite cathode were 5.16, 0.86 and 0.21 Ω cm 2 at the operating temperatures of 600, 700 and 800 °C respectively. The exchange current densities ( i o ) for oxygen reduction reaction (ORR) were determined from the EIS approach, and low-field and high-field cyclic voltammetry. The activation energies ( E a ) of ORR determined from the slope of Arrhenius plots for EIS, low-field and high-field technique were 148.6, 69.8 and 74.2 kJ mol −1 , respectively. Based on the electrochemical properties, the mixed-ionic-and-electronic conductor (MIEC) of SmBa 0.6 Sr 0.4 Co 2 O 5+ δ is a potential cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) based on a SDC electrolyte.

The microstructure, lattice parameters, morphology, mechanical properties, and conductivity of BaCe0.9M0.1O2.95 (M=Gd, Nd, Sm, Y) were systematically investigated under different atmospheres (in air and in wet 5%H2–95%Ar). The XRD results indicated that all of the specimens sintered in air have orthorhombic symmetry, whereas BaCeO3 and BaCe0.9Gd0.1O2.95 decomposed into CeO2 and BaCO3 in their specimens. Secondary CeO2 and BaCO3 might adversely affect the conductivity of BaCeO3-based specimens. The maximum conductivity (σtotal,800 °c=6.46×10−3 S/cm) and minimum activation energy (Ea=52.3 kJ/mol) measured in air were observed for BaCe0.9Y0.1O2.95 among the BaCeO3-based specimens, Whereas in wet 5%H2–95%Ar, the maximum conductivity (σtotal,800 °c=9.20×10−3 S/cm) and minimum activation energy (Ea=55.6 kJ/mol) were measured. The difference in conductivity between the air and wet reducing atmosphere can be explained by the chemical stability. The mechanical properties of BaCe0.9M0.1O2.95 significantly depended on the doping element with the rare-earth oxide dopants affecting the structure stability, grain size, conductivity, thermal expansion, and the mechanical properties. Based on a comprehensive evaluation, BaCe0.9Y0.1O2.95 revealed good chemical stability and high conductivity and thus it is a promising candidate for a proton-conducing electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs).

A Fe–Cr alloy, used for metallic interconnects, was coated with a protective layer of lanthanum strontium manganite (LSMO) using the aerosol deposition method (AD). The effects of the LSMO protective layer, which was coated on the Fe–Cr interconnects using AD, on the area specific resistance (ASR) during high temperature oxidation and the Cr evaporation behaviors were systematically investigated in this paper. The microstructures, morphologies, and compositions of the oxidized scales that appeared on the LSMO-coated Fe–Cr alloy after annealing at 800 °C for 750 h in air were examined using SEM equipped with EDS. The EPMA mapping of the LSMO-coated Fe–Cr interconnects undergoing long term, high-temperature oxidation was used to explain the formation layers of the oxidized scale, which consists of (Mn,Cr) 3 O 4 and Cr 2 O 3 layers. Moreover, the experimental results revealed that the AD process is a potential method for preparing denser protective layers with highly desirable electrical properties for metallic interconnects.

We successfully prepared the TiO 2 @Mn-Zn ferrite composite powder for magnetic photocatalyst. The core Mn-Zn ferrite powder was synthesized by using steel pickling liquor and used alkaline batteries as the starting materials. The shell TiO 2 nanocrystal was prepared by sol–gel hydrolysis precipitation of titanium isopropoxide (Ti(OC 3 H 7 ) 4 ) on the Mn-Zn ferrite powder. The thickness of the titania shell was found to be approximately 2 nm. The core of Mn-Zn ferrite is of spherical or elliptical shape and the particle size of the core is in the range of 20–40 nm. The magnetic Mn-Zn ferrite nanopowder is uniformly encapsulated in a titania layer forming the core–shell structure of TiO 2 @Mn-Zn ferrite powder. The magnetic photocatalyst can be successfully used to treat dye waste waters.

This work reports the characteristics of Sm0.5Sr0.5CoO3−δ (SSC) cathode including its chemical bulk diffusion coefficient (Dchem), current density (i0), and single cell performance. In this study, the value of Dchem is measured by an electrical conductivity relaxation (ECR) technique. The equation of Dchem as a function of temperature in the range of 500–700 °C exhibits as follows: D chem = 4.65 × 10 − 5 exp ( − 91.33 ( kJ mol − 1 ) R T ) ( m 2 s − 1 ) To improve the cathode performance, the active ionic-conductive Ce0.8Sm0.2O1.9 (SDC) nanoparticles deposit on a porous SSC cathode surface by infiltration method. The enhancement in electrochemical performances is ascribed to the creation of electrolyte/cathode phase boundaries, which considerably increases the electrochemical sites for oxygen reduction reaction. In this work, the 0.2 M SDC-infiltrated SSC reveals the maximum peak power density of 489 mW cm−2 at operating temperature of 700 °C with a thin film SDC electrolyte (30 μm), a Ni + SDC anode (1 mm) and a SDC-infiltrated SSC cathode (20 μm).

This work divided into two parts. The first part reports the characteristics of a La 0.8 Ca 0.2 CoO 3− δ (LCCO) cathode including its chemical bulk diffusion coefficient ( D chem ) and chemical surface exchange coefficient ( k chem ) measured by an electrical conductivity relaxation (ECR) technique. The second part reports two methods to improve the performance of solid oxide fuel cells (SOFCs). One is the use of composite cathode, i.e., mixture of 30 wt% electrolyte and 70 wt% cathode. The other is the use of electrolyte-infiltrated cathode, i.e., the active ionic-conductive electrolyte with nanosize was infiltrated onto a porous cathode surface. In this work, the 0.2 M Ce 0.8 Sm 0.2 O 1.9 (SDC)-infiltrated La 0.8 Ca 0.2 CoO 3− δ (LCCO) reveals the maximum peak power density of 305 mW cm −2 at operating temperature of 800 °C with a thin film SDC electrolyte (30 μm), a Ni+SDC anode (1 mm) and a SDC-infiltrated LCCO cathode (20 μm). The enhancement in electrochemical performances by using the electrolyte-infiltrated cathode is ascribed to the creation of electrolyte/cathode phase boundaries, which considerably increase the electrochemical sites for oxygen reduction reaction. Therefore, the infiltrated method is a potential way to improve the performance of SOFCs.

This study investigates the microstructure and electrochemical properties of Sm 0.5 Sr 0.5 Co 0.8 Cu 0.2 O 3− δ (SSC-Cu) cathode infiltrated with Ce 0.8 Sm 0.2 O 1.9 (SDC). The newly formed nanosized electrolyte material on the cathode surface, leading the increase in electrochemical performances is mainly attributed to the creation of electrolyte/cathode phase boundaries, which considerably increases the electrochemical sites for oxygen reduction reaction. Based on the experiment results, the 0.4 M SDC infiltration reveals the lowest cathode polarization resistance ( R P ), the cathode polarization resistances ( R p ) are 0.117, 0.033, and 0.011 Ω cm 2 at 650, 750, and 850 °C, and the highest peak power density, are 439, 659, and 532 mW cm −2 at 600, 700, and 800 °C, respectively. The cathode performance in SOFCs can be significantly improved by infiltrating nanoparticles of SDC into an SSC-Cu porous backbone. This study reveals that the infiltration approach may apply in SOFCs to improve their electrochemical properties.

Modified perovskite ceramics (La 0.9 Ca 0.1 )(Co 1− x Ni x )O 3− δ ( x = 0–0.3) cathodes for solid oxide fuel cells (SOFCs) were synthesized by solid state reaction. The lattice parameters, electrical conductivity, activation energy, and microstructures of these specimens were investigated systematically in this study. The results exhibited that all specimens are rhombohedron structures and their tolerance factors were greater than 0.97, indicating that the perovskite was not distorted by Ni 2+ cation substitution for the B site of (La 0.9 Ca 0.1 )CoO 3− δ . The microstructures of the (La 0.9 Ca 0.1 )(Co 1− x Ni x )O 3− δ specimens showed good densification, and were well-sintered, with few pores. The electrical conductivity behavior conformed to the nature of a semiconductor, for all specimens. As x = 0.1, the electrical conductivity reached the maximum value of 750.3 S/cm at 800 °C, and the activation energy calculated from the Arrhenius plot of the electrical conductivity versus the reciprocal of temperature is 7.1 kJ/mol. The novelty of this study is its introduction of the concept of defect chemistry to explain the relationship between compensation mechanisms and electrical conductivity. The information gleaned regarding charge compensation mechanisms and defect formation may be valuable for a better understanding of the cathode of (La 0.9 Ca 0.1 )(Co 1− x Ni x )O 3− δ ceramics used for SOFCs. Moreover, the information about oxygen content versus temperature is useful for expressing the relationship between electrical conductivity and composition. Therefore, we also used thermogravimetric analysis combined with the room-temperature oxygen content which was determined by iodometric titration to investigate the oxygen content from room temperature to high temperature, in air. Based on the experimental results, the (La 0.9 Ca 0.1 )(Co 0.9 Ni 0.1 )O 3− δ specimen shows high electrical conductivity. Consequently, it is identified as a promising candidate for cathode SOFC applications.

This study investigates Sm 0.5 Sr 0.5 CoO 3− δ (SSC)–Ce 0.8 Sm 0.2 O 1.9 (SDC) composite cathodes with a gradual change in composition from electrolyte to the cathode in an attempt to discover a potential approach applicable to solid oxide fuel cells (SOFCs). The gradual change in composition from electrolyte to cathode shows the decline in charge transfer resistance ( R 2 ) and gas phase diffusion resistance ( R 3 ). Because the value of R 3 is always larger than R 2 and R 3 significantly dominates the total cathode polarization resistance ( R P ) at temperatures within the range of 750–850 °C, i.e., in this temperature range, the rate-determining step is dominated by the diffusion or dissociative adsorption of oxygen. The functionally gradient cathode with a graded interface between cathode and electrolyte reveals both a higher exchange current density ( i 0 ) and a lower activation energy for oxygen reduction reaction (ORR), which suggests that the ORR kinetics can be improved by using the configuration of a functionally gradient cathode.

The microstructure, lattice parameters, mechanical properties, and electrical conductivity mechanisms for Cu doping on B-site of (La0.8Ca0.2)(Cr0.9Co0.1)O3−δ have been systematically investigated. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of hole with the electrical conductivity. The information of charge compensation mechanisms and defect formation may be valuable for a better understanding of the interconnect of (La0.8Ca0.2)CrO3−δ-based ceramics used for solid oxide fuel cells (SOFCs). The electrical conductivity increases with the increase in temperature in air, whereas the electrical conductivity has a maximum value at a certain temperature in 5% H2–95% Ar. The concentration of hole at high oxygen activity is larger than that at low oxygen activity. Because (La0.8Ca0.2)CrO3−δ-based ceramics are p-type conductors, the electrical conductivity is dominated by the concentration of hole. Obviously, the electrical conductivities of Cu doping on B-site of (La0.8Ca0.2)(Cr0.9Co0.1)O3−δ in air are larger than those in 5% H2–95%. At higher Cu-doping levels, higher temperatures, and high oxygen activity, the compensation mechanism is significantly dominated by the formation of oxygen vacancy, i.e. ionic compensation. On the contrary, the compensation mechanism is significantly dominated by the formation of the formation of Cr4+, i.e. electrical compensation at lower Cu-doping levels, higher temperatures, and lower oxygen activity. Because mechanical properties of SOFCs interconnect materials are very important in reducing atmosphere, the effect of atmospheres on fracture toughness and microhardness for specimens is investigated, which results revealed that when specimens were exposed to 5% H2–95% Ar forming gas, all specimens appeared to have hydrogen-induced cracking (HIC) except for (La0.8Ca0.2)(Cr0.87Co0.1Cu0.03)O3−δ. Although the exact mechanism of HIC is still not clear, it is known from this study that Cu doped in the B-site of (La0.8Ca0.2)(Cr0.9Co0.1)O3−δ enhanced HIC damage and with the increase of Cu-doping level, the degree in HIC is increased.

The electrical conduction behaviors of isovalent and acceptor dopants on B site of (La 0.8 Ca 0.2 )CrO 3− δ perovskites at high and low oxygen activities were investigated systematically. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of electron hole with the electrical conductivity. The information of charge compensation mechanisms and defect formation may be valuable for a better understanding of the interconnect of (La 0.8 Ca 0.2 )CrO 3− δ -based ceramics used for solid oxide fuel cells (SOFCs). Since (La 0.8 Ca 0.2 )CrO 3− δ -based specimens belong to p-type conductors, their conductivities are proportional to the concentration of electron hole. In reducing atmosphere, the oxygen may be lost and ionic compensation may be take place through the formation of oxygen vacancies and the electrical compensation may arise by changing the valence of Cr from tri-valence to tetra-valence in reducing atmosphere. However the formation of oxygen vacancies has no contribution to electrical conductivity, the compensation mechanism is dominated by the electrical compensation, i.e . the take place a transition of Cr 3+ → Cr 4+ rather than that of ionic compensation, i.e. the formation of oxygen vacancies. Based on the defect chemical reactions and the results of electrical conductivity, the concentration of electron hole at high oxygen activity is larger than that at low oxygen activity. Therefore the electrical conductivity of (La 0.8 Ca 0.2 )CrO 3− δ -based ceramics at air is larger than that at 5% H 2 –95% Ar forming gas. The compensation mechanisms contain ionic and electrical compensation and the ratios of electrical to ionic compensation varied with the kind of dopant which significantly effects the electrical conductivity. The results suggest that the (La 0.8 Ca 0.2 )Cr 0.9 Co 0.1 O 3− δ specimen shows high electrical conductivity in air ( σ 850 °C = 59.59 S/cm) and 5% H 2 –95% Ar forming gas ( σ 850 °C = 47.98 S/cm) leading it a promising candidate as an interconnect material for SOFCs applications.

The mixed ionic and electronic conductors (MIEC) of La 0.9 Sr 0.1 Co 0.8 Ni 0.2 O 3−δ (LSCN)–Ce 0.8 Sm 0.2 O 1.9 (SDC) were investigated for potential application as a cathode material for solid oxide fuel cells (SOFCs) based on a SDC electrolyte. Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600–850 °C to determine the cathode polarization resistance, which is represented by area specific resistance (ASR). This study systematically investigated the exchange current densities ( i 0 ) for oxygen reduction reaction (ORR), determined from the EIS data and high-field cyclic voltammetry. The 70LSCN–30SDC composite cathode revealed a high exchange current density ( i 0 ) value of 297.6 mA/cm 2 at 800 °C determined by high-field technique. This suggested that the triple phase boundary (TPB) may spread over more surface of this composite cathode and revealing a high catalytically active surface area. The activation energies ( E a ) of ORR determined from the slope of Arrhenius plots for EIS and high-field techniques are 96.9 kJ mol −1 and 90.4 kJ mol −1 , respectively.

The microwave dielectric properties of Sm(Mg 0.5 Ti 0.5 )O 3 incorporated with various amount of Bi 2 O 3 and B 2 O 3 additives have been investigated systematically. In this study, both Bi 2 O 3 and B 2 O 3 additives acting as a sintering aid can effectively lower the sintering temperature from 1550 °C to 1300 °C. The ionic radius of Bi 3+ for a coordination number of 6 is 0.103 nm, whereas the ionic radius of B 3+ is 0.027 nm. Clearly, the ionic radius of Bi 3+ is greatly larger than one of B 3+ , which resulted in the specimens incorporated with Bi 2 O 3 having larger lattice parameters and cell volume than those incorporated with B 2 O 3 . The experimental results show that no second phase was observed throughout the entire experiments. Depending on the interfacial tension, the liquid phase may penetrate the grain boundaries completely, in which case the grains will be separated from one another by a thin layer as shown in Sm(Mg 0.5 Ti 0.5 )O 3 ceramics incorporated with Bi 2 O 3 . Whereas, in Sm(Mg 0.5 Ti 0.5 )O 3 ceramics incorporated with B 2 O 3 , the volume fraction of liquid is high, the grains may dissolve into the liquid phase, and rapidly rearrange, in which case contact points between agglomerates will be dissolved due to their higher solubility in the liquid, leading plate-like shape microstructure. A dielectric constant ( ɛ r ) of 29.3, a high Q × f value of 26,335 GHz (at 8.84 GHz), and a τ f of −32.5 ppm/°C can be obtained for Sm(Mg 0.5 Ti 0.5 )O 3 ceramics incorporated with 10 mol% Bi 2 O 3 sintered at 1300 °C. While Sm(Mg 0.5 Ti 0.5 )O 3 ceramics incorporated with 5 mol% B 2 O 3 can effectively lower temperature coefficient of resonant frequency, which value is −21.6 ppm/°C. The Sm(Mg 0.5 Ti 0.5 )O 3 ceramic incorporated with heavily Bi 2 O 3 and B 2 O 3 additives exhibits a substantial reduction in temperature (∼250 °C) and compatible dielectric properties in comparison with that of an un-doped one. This implied that this ceramic is suitable for miniaturization in the application of dielectric resonators and filters by being appropriately incorporated with a sintering aid.

The mixed ionic and electronic conductors of La 0.9 Ca 0.1 Ni 0.5 Co 0.5 O 3 –Ce 0.8 Sm 0.2 O 1.9 (LCNC–SDC) are investigated systematically for potential application as a cathode for solid oxide fuel cells based on a Ce 0.8 Sm 0.2 O 1.9 (SDC) electrolyte. The electrochemical impedance spectroscopy (EIS) measurements are performed in air over the temperature range of 600–850 °C to determine the cathode polarization resistance. The exchange current densities for oxygen reduction reaction (ORR), determined from the low-field cyclic voltammetry, high-field cyclic voltammetry, and EIS data are systematically investigated. The activation energies ( E a ) for ORR determined from the slope of Arrhenius plots are in the range of 102.33–150.73 kJ mol −1 for LCNC–SDC composite cathodes. The experimental results found that LCNC–SDC (70:30) composite cathode has a maximum exchange current density and a minimum polarization resistance of 0.30 Ω cm 2 for 850 °C among LCNC–SDC composite cathodes.

The lattice parameters, electrical conductivity, activation energy, mechanical properties, and microstructure of (La0.8Ca0.2)CrO3−δ-based specimens were investigated systematically in this paper. The tolerance factors for (La0.8Ca0.2)CrO3−δ-based specimens were all greater than 0.9, indicating the perovskite was not distorted with different cations (Al3+, Co3+, Cu2+, Fe3+) substitution for B site of (La0.8Ca0.2)CrO3−δ. (La0.8Ca0.2)Cr0.9Co0.1O3−δ specimen revealed the maximum electrical conductivity, σ850 °C = 59.59 S/cm with minimum activation energy, Ea = 11.2 kJ/mol among (La0.8Ca0.2)CrO3−δ-based specimens. The grain size seemed dependent on doping species and the grain sizes were distributed in the range of 2.4–5.6 μm for (La0.8Ca0.2)CrO3−δ-based specimens. The rate of grain growth was proportional to the boundary mobility Mb, which was related to the diffusion coefficient of doping cation. (La0.8Ca0.2)CrO3−δ-based specimens revealed variety in microhardness, in the range of 4.33–9.85 GPa and the fracture toughness were distributed in the range of 3.52–4.33 MPa m1/2. Based on the results in terms of grain size and mechanical properties, we concluded that the microhardness and fracture toughness were dependent on the dopant ions. The (La0.8Ca0.2)Cr0.9Co0.1O3−δ specimen shows high electrical conductivity and mechanical properties Consequently, it is a promising candidate as an interconnect material for intermediate temperature solid oxide fuel cell (IT-SOFC) applications.

The mixed ionic and electronic conductors (MIECs) of Sm 0.5 Sr 0.5 Co 0.4 Ni 0.6 O 3−δ (SSCN)–Sm 0.2 Ce 0.8 O 1.9 (SDC) were investigated for potential application as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) based on an SDC electrolyte. Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600–850 °C to determine the cathode polarization resistance which is represented by area specific resistance (ASR). To investigate the ORR mechanism, the impedance diagram for 70SSCN–30SDC was measured under applied cathodic voltage from E = 0.0 to E = −0.3 V. It indicated that the charge transfer dominated the rate-determining step at the temperature of 600 °C; whereas the diffusion or dissociative adsorption of oxygen dominated the rate-determining step at the temperature of 800 °C. In this study, the exchange current density ( i 0 ) for oxygen reduction reaction (ORR) was determined from the EIS data. The i 0 value of 70SSCN–30SDC/SDC was 187.6 mA cm −2 which is larger than the i 0 value of 160 mA cm −2 for traditional cathode/electrolyte, i.e. LSM/YSZ at 800 °C, indicating that the 70SSCN–30SDC composite cathode with a high catalytically active surface area could provide the oxygen reduction reaction areas not only at the triple-phase boundaries but also in the whole composite cathode.

This study investigated the electrochemical corrosion properties of the solders for die-attach applications in 3.5% NaCl solution. Compared with Pb–5Sn and Zn–40Sn, Bi–11Ag exhibited higher corrosion potential and relatively low corrosion current density. The ductile Ag-rich phase which dispersed in the Bi matrix was able to accommodate the stress arising from the formation of a passive layer and contributed to the two-stage passivation. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirm that the corrosion products comprised BiOCl, Bi 2 O 3 and AgCl.

Copper ferrite nanopowders were successfully synthesized by a microwave-induced combustion process using copper nitrate, iron nitrate, and urea. The process only took a few minutes to obtain CuFe 2 O 4 nanopowders. The resultant powders were investigated by XRD, SEM, VSM, and surface area measurement. The results revealed that the CuFe 2 O 4 powders showed that the average particle size ranged from 300 to 600 nm. Also, it possessed a saturation magnetization of 21.16 emu/g, and an intrinsic coercive force of 600.84 Oe, whereas, upon annealing at 800 °C for 1 h. The CuFe 2 O 4 powders specific surface area was 5.60 m 2 /g. Moreover, these copper ferrite magnetic nanopowders also acted as a catalyst for the oxidation of 2,3,6-trimethylphenol to synthesize 2,3,5-trimethylhydrogenquinone and 2,3,5-trimethyl-1,4-benzoquinone for the first time. On the basis of experimental evidence, a rational reaction mechanism is proposed to explain the results satisfactorily.

Magnesium-substituted lithium ferrite of different composition (Li0.5Fe2.5−xMgxO4−δ) were prepared for x = 0.0–1.0 by conventional ceramic technique. The crystal structure characterization and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). Initial permeability and quality factor were measured in the frequency range of 1 kHz to 100 MHz. The permeability decreased gradually from μ (f = 10 MHz) = 34.0 for Li0.5Fe2.5O4 to μ (f = 10 MHz) = 11.5 for Li0.5Fe1.5Mg1.0O4. Electrical conductivity measurements were carried in the range of 250–700 °C in air. The maximum electrical conductivity, σ700 °C = 0.1274 S/cm has been found to be for Li0.5Fe2.5O4 specimen. With increasing Mg-substituted content, the decreased in the electrical conductivity.

Bi2O3 was selected as liquid phase sintering aid to lower the sintering temperature of La(Mg0.5Ti0.5)O3 ceramics. The sintering temperature of La(Mg0.5Ti0.5)O3 ceramics is generally high, about 1600 °C. However, the sintering temperature was significantly lowered about 275 °C from 1600 °C to 1325 °C by incorporating in 15 mol% Bi2O3 and revealed the optimum microwave dielectric properties of dielectric constant (ɛr) value of 40.1, a quality factor (Q × f) value of 60,231 GHz, and the temperature coefficient (τf) value of 70.1 ppm/°C. During all addition ranges, the relative dielectric constants (ɛr) were different and ranged from 32.0 to 41.9, the quality factors (Q × f) were distributed in the range of 928–60,231 GHz, and the temperature coefficient (τf) varies from 0.3 ppm/°C to 70.3 ppm/°C. Noticeably, a nearly zero τf can be found for doping 5 mol% Bi2O3 sintering at 1325 °C. It implies that nearly zero τf can be achieved by appropriately adjusting the amount of Bi2O3 additions and sintering temperature for La(Mg0.5Ti0.5)O3 ceramics.

The microstructure, thermal expansion, microhardness, indentation fracture toughness, and ionic conductivity of neodymium-doped ceria (NDC) prepared by coprecipitation were investigated. The results revealed that the average particle size ( D BET ) ranged from 20.1 to 25.8 nm, crystallite dimension ( D XRD ) varied from 17.5 to 20.7 nm, and the specific surface area distribution was from 31.25 to 40.27 m 2 /g for neodymium-doped ceria stacking powders. Dependence of lattice parameter, a , versus dopant concentration, x , of Nd 3+ ion shows that these solid solutions obey Vegard's rule as a ( x ) = 5.4069 + 0.1642 x for Ce 1− x Nd x O 2−(1/2) x for x = 0.05–0.25. For neodymium-doped ceria ceramics sintered at 1500 °C for 5 h, the bulk density was over 95% of the theoretical density. The maximum ionic conductivity, σ 800°C = 4.615 × 10 −2 S/cm, with the minimum activation energy, E a = 0.794 eV was found for the Ce 0.75 Nd 0.25 O 1.875 ceramic. Trivalent, neodymium-doped ceria ceramics revealed high fracture toughness, the fracture toughness distribution was in the range of 6.236 ± 0.021 to 6.846 ± 0.017 MPa m 1/2 . The high indentation fracture toughness of neodymium-doped ceria was attributed to crack deflection. Moreover, the porosity may influence the mechanical properties such as microhardness and fracture toughness. It was observed that as the porosity reduced, the microhardness and fracture toughness increased.

Characteristics, such as lattice parameter, theoretical densities, thermal expansion, mechanical properties, microstructure, and ionic conductivities, of Ce0.8M0.2O2−δ (M = Y, Gd, Sm, Nd, La) ceramics prepared by coprecipitation were systematically investigated in this paper. The results revealed that the lattice parameter and density based on the oxygen vacancy radius generally agreed with experimental results. Ce0.8Sm0.2O2−δ ceramic sintered at 1500 °C for 5 h possessed the maximum ionic conductivity, σ800 °C = 6.54 × 10−2 S cm−1, with minimum activation energy, Ea = 0.7443 eV, among Ce0.8M0.2O2−δ (M = Y, Gd, Sm, Nd, La) ceramics. The thermal expansion coefficients of Ce0.8M0.2O2−δ (M = Y, Gd, Sm, Nd, La) were in the range of 15.176–15.571 ppm/°C, which indicates that the rare-earth oxide dopants have insignificant influence on the thermal expansion property. Trivalent, rare-earth oxide doped ceria ceramics revealed high fracture toughness, with the fracture toughness in the range of 6.393–7.003 MPa m1/2. According to SEM observation, the cracks are limited to one grain diameter; therefore, the high fracture toughness of rare-earth oxide doped ceria may be due to the toughness mechanism of crack deflection at the grain boundary. Based on the results of grain size and mechanical properties, one may conclude that there is no significant dependence of fracture toughness and microhardness for Ce0.8M0.2O2−δ ceramics on grain size. Correlation between the grain size of Ce0.8M0.2O2−δ ceramics and the dopant species can be explained on the basis of the concept of the rate of grain growth being proportional to the boundary mobility Mb. This leads to a conclusion that the diffusion coefficient of La in Ce0.8La0.2O2−δ>Nd in Ce0.8Nd0.2O2−δ>Sm in Ce0.8Sm0.2O2−δ>Gd inCe0.8Gd0.2O2−δ>Y in Ce0.8Y0.2O2−δ.