Space Group Fm3m Research Articles

Phase equilibrium diagram of Y-Cu-Sb system at 870 K

The interaction of the components in the Y-Cu-Sb ternary system was investigated using the methods of X-ray phase analysis, microstructure, and energy-dispersive X-ray spectroscopy in the whole concentration range at 870 K. At the temperature of investigation Y-Cu-Sb system is characterized by the formation of three ternary compounds: Y3Cu22Sb9 (Dy3Cu20+xSb11-x structure type, space group F-43m, a=1.6614(3) nm), Y3Cu3Sb4 (Y3Au3Sb4 structure type, space group I-43d, а=0.95357(5) nm), YCuSb2 (HfCuSi2 structure type, space group P4/nmm, a=0.42580(1), c=0.98932(3) nm). The solubility of copper in the binary compound YSb (NaCl structure type) extends up to 8 at. %.

Synthesis of prussian blue analog (Co/TCNi/HCCr) nanoparticles using a facile co-precipitation approach and evaluation of their dielectric characteristics for electronic applications

The Prussian blue analog Co0.4/(TCNi)0.2/(HCCr)0.6 (PBA) nanoparticles were synthesized via a chemical co-precipitation approach. The structural characteristics of the nanocomposite (NCp) were investigated using the XRD technique, which revealed that the synthetic PBA has a tiny crystallite size and poor crystallinity. The XRD analysis suggests that the fabricated NCp has a face-centered cubic structure with space group Fm-3 m. For deep microstructure analysis, SEM, EDX, and AFM were employed to describe the topological nature and surface architecture. It is observed that the PBA nanocomposite has a small crystallite size of ~13.66 ± 0.32 nm. The particles’ surface displays a high degree of homogeneity, while the grain boundaries are clearly discernible, presenting a spherical morphology with an average diameter of 22 ± 2.1 nm. The porosity was ascertained from an AFM image of approximately 140. Furthermore, the value of the average roughness (Rs) is 6.86 nm. The AC conductivity of PBA in disc form was calculated at various temperatures and frequencies. The results indicate that the dielectric constant (ɛ′) of PBA nanoparticles exhibits a rise from 163 to 3464 throughout the frequency range of 10–100 kHz at ambient temperature and from 27 to 6000 at 293 K. This finding provides confirmation that the dielectric characteristics of PBA nanoparticles are enhanced during the process of annealing. The values of the exponent factor (s) range from 0 to 1; this behavior is connected to the correlated barrier hopping model (CBHM) for AC conductivity. The value of WM was ascertained to be 1.69 eV. Furthermore, the values of activation energy were calculated, and these values decreased from 0.20 to 0.17 eV with annealing. The change in loss tangent (tanδ) as a function of angular frequency at various temperatures is also shown. The investigation of the dielectric characteristics was measured over a wide range of frequencies and temperatures to get valuable data about the dissipation properties of the prospective electronic applications.

Structural Studies of Potassium Hexaiodoplatinate(IV) K2PtI6

The temperature dependence of the crystal structure of Potassium Hexaiodoplatinate(IV) between 80 and 500 K is described. Below 410 K, K2PtI6 adopts a monoclinic structure described in space group P21/n due to the presence of tilting of the PtI6 octahedra. Heating the sample to above 410 K results in the loss of the out-of-phase tilts and a transition to the previously described tetragonal structure in space group P4/mnc. The remaining in-phase tilts are lost upon heating to above 460 K where the structure is cubic in space group Fm3‾m.It is anticipated that the identification of accurate structures for the three polymorphs of K2PtI6 will stimulate further theoretical and practical studies.

Lead-free silver-indium based halide double perovskites for energy harvesting applications

Herein, density functional theory (DFT) is utilized to analyze physical characteristics of two novel halide double perovskites (HDPs) Na2AgInBr6 and K2AgInBr6. Exchange and correlation energies were estimated via employing generalized gradient approximation (GGA) along with modified Becke-Johnson (mBJ) potential. Geometry optimization predicted nonmagnetic ground state for both HDPs with cubic structure having Fm3m space group. Computed formation enthalpies (ΔHf) and tolerance factors (τG) revealed the thermodynamically stability of both compounds in cubic phase. Na2AgInBr6 is regarded as brittle while K2AgInBr6 is ductile in nature. Na2AgInBr6 exhibited a band gap (Eg) of 1.39 eV while K2AgInBr6 has a Eg of 1.41 eV. Density of states analysis reveals that 4d of Ag- and 4p of Br states are majorly contributing in the higher valence band while In-5s and 4p of Br states are present in lower conduction band and all these states define the semiconductive nature of these systems. Both HDPs are optically active in visible light region suggesting the suitability for solar cell applications. Thermoelectric efficiency is also computed in terms of figure of merit (ZT(e)) whose values for both compounds are 0.7. Based on these outcomes, both HDPs can be considered as highly suitable candidates for energy harvesting applications.

Exploring the structural and optical properties of Eu3+, Sb3+ co-doping effect on Cs2NaInCl6 double perovskites for LEDs applications

In the present study Eu3+, Sb3+ co-doped Cs2NaInCl6 double perovskite has been synthesized by using the hot injected method. The crystal structure of the prepared samples has been investigated by XRD data with the help of Rietveld refinement analyzes. The obtained structural property result revealed that all the samples [Cs2NaInCl6, Sb3+ doped Cs2NaInCl6 and (Sb3+, Eu3+) co-doped Cs2NaInCl6] are crystallized in a cubic crystal structure with a space group Fm-3m (225). Further, the electronic properties have been performed by using UV absorbance spectroscopy. It shows that the electronic band gap of the Cs2NaInCl6 and Sb3+ doped compounds exhibits 4.8 eV and 3.9 eV respectively, which is good agreement with other results. The energy band gap value of Eu3+, Sb3+ co-doped Cs2NaInCl6 compounds exhibited ∼4.0 eV, which is very close to Sb3+ doped Cs2NaInCl6 double perovskite. The Photoluminescence study revealed that Sb3+, Eu3+ co-doped Cs2NaInCl6 compounds exhibited dual emission from the self trapped excitation to Eu3+ ion. The blue emission (440 nm) is due to the transition of 3P1→1S0 from Sb3+ ion and orange-red emissions (570–706 nm) are due to the transition of 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 from Eu3+ ions. The dual emission behavior of the Sb3+, Eu3+ co-doped Cs2NaInCl6 double perovskites suitable for optoelectronic devices and light emitting diodes (LED's) applications.

Novel synthesis of stabilized Bi1–x–yGdxDyyO1.5 solid electrolytes with enhanced conductivity for intermediate temperature solid oxide fuel cells (SOFCs)

Herein, we report the synthesis of a Dy–Gd co-doped cubic phase-stabilized Bi2O3 solid electrolyte system via solid-state processing under atmospheric conditions. Doping with Dy3+ and Gd3+ has been observed to significantly enhance the densification process during sintering for stabilization purposes, thereby improving the electrical properties of δ-Bi2O3-type polymorphs. The synthesized ceramics were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FESEM-EDX), thermal gravimetry/differential thermal analysis (TG/DTA), and the four-point probe technique (4PPT). XRD analysis reveals that the samples Bi1–x–yGdxDyyO1.5 (y = 0.05/x = 0.05, 0.10, 0.15, and 0.20, and x = 0.05/y = 0.10, 0.15, and 0.20) exhibit a stable face-centered cubic δ-phase and a mixed-phase crystallographic structure. The XRD analysis of the stabilized δ-phase suggests that the prepared oxides show a face-centered cubic (FCC) structure with a space group of Fm-3m. FESEM micrographs reveal that the composition Bi0.90Gd0.05Dy0.05O1.5 has no significant holes. Nevertheless, an evident increase in the pore formation is observed as the amount of Gd2O3 increases until it reaches 20%. This finding suggests that dense pellets are formed during the sintering process at 900–1000 °C. The DTA analyses were performed to verify the phase stability, which agrees with the XRD results. The electrochemical performance of the synthesized Dy–Gd co-doped Bi2O3 solid electrolyte system was evaluated and analyzed in detail by using the electrochemical impedance spectroscopy (EIS) technique. Based on EIS and conductivity measurements, Bi0.75Gd0.20Dy0.05O1.5 exhibits the lowest activation energy of 0.519 eV and the highest conductivity value of 0.398 S/cm at 627 °C compared to the other samples; this composition can be used as a solid electrolyte for intermediate-temperature solid oxide fuel cells (SOFCs).

Atomic order, magnetic and transport phenomena in half-Heusler CoMnSb0.9Z0.1 alloys (Z = Si, Al, Sn, and Bi)

In this study, we investigate the effects of doping with ∼10 at% of Si, Al, Sn, and Bi on the atomic order, microstructure, and magnetic properties of CoMnSb samples prepared using the arc-melting method. X-ray diffraction, scanning electron microscopy, and magnetometry techniques were employed to derive the structural and magnetic parameters. The samples demonstrate a superstructure with an Fm-3m space group. They exhibit a saturation moment of 3.71–4.71 μB per formula unit at 5 K and a Curie temperature ranging from 474 to 507 K. Rietveld refinement performed on the XRD data revealed a possible occupation of magnetic atoms in the vacant 32f (x’, x’, x’) sites and atomic swapping, both of which may affect the magnitudes of the magnetic moment and Curie temperature. The electrical measurement results show that the grain boundaries and voids govern the conductivity of the samples. The spin polarization of the Si-doped sample was determined based on the grain-boundary magnetoresistance effect, which showed that this sample has a high degree of atomic order, consistent with the low magnetic moment, Curie temperature, and lattice constant.

Conflicting primary and secondary properties of thermoelectric devices – A case study on the thermomechanical behavior of ZrNiSn

While the primary properties of thermoelectric devices, directly related to the conversion efficiency, are considered in design efforts, the secondary (thermomechanical) properties are often ignored or overlooked even though they can lead to failure. Here, thermomechanical properties of thermoelectric ZrNiSn in the amorphous and crystalline state (space group F-43m), comprising thermal conductivity, thermal expansion, elastic (Young’s) modulus, and thermal shock, are studied using density functional theory and two phonon models. Thermal conductivity is also a key primary property for thermoelectric applications. Amorphous ZrNiSn exhibits a fourfold lower thermal conductivity than the crystalline counterpart due to high phonon–phonon scattering, which is conducive to thermoelectric performance. However, this is conflicting since a high thermal conductivity value is required to attain high resistance to thermal shock. Due to stronger bonds in the crystalline counterpart, facilitated by the stronger Zr3d–Ni3d and Sn5p–Ni3d hybridization and higher coordination than in the amorphous state, the linear coefficient of thermal expansion is lower, and the elastic modulus is higher. Hence, the crystalline state yields higher resistance to thermal shock. It is suggested that samples entailing both amorphous and crystalline regions can concurrently satisfy the primary and secondary requirements for enhanced efficiency and durability.

Confirming the structural stability and reaching the depth of quaternary Heusler alloys LiMgAgZ (Z = Al, Ga) for thermoelectric device applications: A first-principles study

First principles calculations including structural, electronic, elastic, vibrational, thermodynamic and thermoelectric properties of novel quaternary Heusler compounds LiMgAgZ (Z = Al, Ga) have been studied for the first time using density functional theory (DFT). The quaternary Heusler structured LiMgAgAl and LiMgAgGa alloys possess a face centered cubic structure and belong to the space group F-43m (group No. 216). The band structure calculations reveal that these compounds are metallic. Further, the Fermi surface studies have demonstrated their metallic behavior. The mechanical stability is predicted based on calculated elastic constants, Poisson’s ratio as well as other mechanical parameters. The thermoelectric nature of these compounds is studied utilizing BoltzTrap code. The phonon dispersion curves of LiMgAgZ (Z = Al, Ga) are in the high symmetry directions over the Brillouin zone which indicate the vibrational stability of these compounds. The phonon modes are observed to be Raman active or Infrared active based on the representation of Eigenvectors. The stability of the compounds is also analyzed for their thermodynamic applications. The calculated results reveal unique surface topologies and thermoelectric responses for the compounds under investigation. This work is carried out to inspire researchers to synthesize such types of compounds and analyze their potential for the development of modern thermoelectric devices.

Intriguing and Facile Preparation Approach of CdO Nanorod-Based Abundant Chitosan for Symmetric Supercapacitors.

Abundant chitosan was rationally used for the green fabrication of cadmium oxide nanorods (CdO nanorods) owing to its environmentally benign characteristics, bioavailability, low cost, etc. However, the primary unsubstituted amino group of chitosan interacts with the surface of Cd salt at higher temperatures, resulting in CdO nanorod formation. A one-step hydrothermal technique was adopted in the presence of chitosan. Optical, structural, and morphology techniques characterized CdO nanorods. According to X-ray diffraction crystallography, CdO is well crystallized in the face-centered cubic lattice with an Fm-3m (225) space group. The AC@CdO nanoelectrode demonstrated an outstanding gravimetric capacitance of 320 F g-1 at a current density of 0.5 A g-1, nearly three-fold that of ordinary AC electrodes. The AC electrode and the AC@CdO nanoelectrode retain 90 and 93% of their initial specific capacitance after 10,000 galvanostatic charge discharge cycles. The AC@CdO nanoelectrode has a lower equivalent series resistance value than the AC electrode. Moreover, AC@CdO symmetric supercapacitor devices achieve excellent results in terms of specific energy, specific power, and capacitance retention.

A low-temperature face-centered-cubic polymorph of Cu6GeWSe8 with a semiconductor-like conductivity

Hexagonal Cu6GeWSe8 (H-phase) with an intermediate band gap has been reported lately. In this paper, we show a low-temperature face-centered-cubic modification of Cu6GeWSe8 (C-phase), which crystallizes in the noncentrosymmetric space group F-43m with four formula in the cell of dimension a = 11.1372(2) Å. In the C-phase, double layers organized by MeSe4 (Me = Cu, Ge and W) tetrahedra alternately stack along the <111> direction. A weakly first-order or nearly second-order displacive phase transition from cubic to hexagonal polytypes undergoes initially at ∼ 440 °C upon increasing temperature. Electrical resistivity and Seebeck coefficient reveal a semiconductor-like conduction with holes as the predominant charge carriers. The semiconductivity is also supported by the almost zero electronic specific-heat coefficient γ. The mechanism of thermal conduction was analyzed by abstracting electronic and lattice thermal conductivities through thermal transport measurement and meanwhile the thermoelectric properties were characterized. The differences in band structures and formation energy between the two variants were studied by ab-initio calculations, which indicate that the H-phase is a semiconductor and the C-phase is a semimetal with low density of states, and the hexagonal modification is comparatively stable. The cubic polytype of Cu6GeWSe8 expands the Cu-Ge-W-Se system. A stereo phase diagram making reviews on the rich materials, and multiple crystallographic and electronic states in this system was established, which would be helpful to guide for seeking new materials and to probe the interplay between polymorphism and property in chalcogenide family.

Structural stability and magnetic properties of Ni nanoparticles with an in situ formed surface stabilization layer of graphitic-carbon

Finely dispersed spherical-shaped Ni nanoparticles, surface stabilized by a thin layer of in situ formed graphitic-carbon, were synthesized by a simple process involving heat-treatment of a complex precursor of Ni2+-poly-vinyl alcohol (PVA)-sucrose in Ar atmosphere at selected temperatures in the range of 400–600°C. The structural and compositional properties of the Ni nanoparticles were analyzed with X-ray diffraction (XRD), thermal analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). All the samples showed stable face-centered cubic (fcc) structure of Ni (Fm3m space group). Microstructural analysis disclosed the narrow size distribution of the Ni nanoparticles. The surface structure of the nanoparticles was evaluated by Raman and XPS techniques. The surface layer of graphitic-carbon ensures the structural stability of the nanoparticles even at a high temperature of 1200°C. The magnetic properties of the samples were analyzed at room-temperature with a vibrating sample magnetometer (VSM).

Effect of deposition temperature on topography and electrochemical water oxidation of NiO thin films

The deposition temperature plays a significant role in controlling the crystallinity, morphology, and texture of thin films. Herein, we report the fabrication of nickel oxide thin films on a fluorine-doped tin oxide-coated glass substrate via a single-step aerosol-assisted chemical vapor deposition technique. Variable temperatures from 450 to 525 °C were used for the fabrication of these NiO thin films. The crystalline structure of nickel oxide thin films was determined by X-ray diffraction which showed cubic structure having space group Fm3m, and unit cell lattice parameters of a = b = c = 4.17 Å that crystallize preferentially along (200) plane. While the Raman spectroscopic study revealed the presence of peaks corresponding to nickel oxide structure. The surface chemical composition and oxidation states were investigated by X-ray photoelectron spectroscopy. Moreover, field-emission scanning electron microscopy aided in examining the temperature-dependent topography and microstructure of films. It was observed that when deposition temperature is increased from 450 to 525 °C, the bandgap energy decreased from 3.59 to 3.41 eV. The electrocatalytic activity for the oxygen evolution reaction was performed under alkaline conditions, using linear sweep voltammetry and cyclic voltammetry at different scan rates. Moreover, ohmic drop and charge transfer resistance are estimated by electrochemical impedance spectroscopy. The nickel oxide deposited at 500 °C showed the highest current density and the earliest onset overpotential as compared with other samples at different temperatures. Morphology-dependent catalytic activity is attributed to substrate temperature which significantly affects the growth of nickel oxide. Cyclic voltammetry reveals the Ni redox feature due to the active phase of nickel (oxy)hydroxide (NiOOH) and there was no significant current until 1.5 VRHE. Measurements of activity as a function of substrate temperature were consistent with the hypothesis that different morphology of the electrode exerts different charge transfer activation on nickel oxide. These results suggested that electrocatalysts coupled with controlled morphology can be tuned in terms of high performance, commercial applicability, and water-splitting devices.

Plectranthus barbatus Leaf Extract-Mediated Synthesis of ZnS and Mg-Doped ZnS NPs: Structural, Optical, Morphological, and Antibacterial Studies

In the current study, the researchers have explored the influence of doped Mg ions on the optical, morphological, and structural properties of zinc sulfide (ZnS) nanoparticles (NPs). The green technique was employed to prepare pure and 2% and 5% Mg-doped ZnS NPs using the Plectranthus barbatus leaf extract as a capping agent. XRD, SEM, FTIR, and UV-visible were used in the investigation process. The XRD results showed that all the synthesized materials have a cubic structure with space group F-43m. The Dav was nearly in the range of 2.02–2.20 nm. The SEM images illustrated that NPs were agglomerated. The UV-visible results showed that the optical bandgap increased as Mg2+ ions increased, which was in the range of 3.81–4.42 eV. The absorption shoulder of the prepared NPs is blue-shifted with increasing dopant concentration. The FTIR spectrum gives characteristic peaks for Zn-S bonds and asserts NPs’ formation. The antibacterial check against E. coli and S. aureus bacterial strains revealed that pure and Mg-doped ZnS NPs have higher activity for both bacterial strains. The results have shown that the prepared materials can be used for antibacterial activities and optoelectronic applications.

Mechanical and Structural Characterization of Laser-Cladded Medium-Entropy FeNiCr-B4C Coatings.

Equiatomic medium-entropy alloy (MEA) FeNiCr-B4C (0, 1, and 3 wt.% B4C) coatings were deposited onto an AISI 1040 steel substrate using pulsed laser cladding. Based on an SEM microstructural analysis, it was found that the cross-sections of all the obtained specimens were characterized by an average coating thickness of 400 ± 20 μm, a sufficiently narrow (100 ± 20 μm) "coating-substrate" transition zone, and the presence of a small number of defects, including cracks and pores. An XRD analysis showed that the formed coatings consisted of a single face-centered cubic (FCC) γ-phase and the space group Fm-3m, regardless of the B4C content. However, additional TEM analysis of the FeNiCr coating with 3 wt.% B4C revealed a two-phase FCC structure consisting of grains (FCC-1 phase, Fm-3m) up to 1 µm in size and banded interlayers (FCC-2 phase, Fm-3m) between the grains. The grains were clean with a low density of dislocations. Raman spectroscopy confirmed the presence of B4C carbides inside the FeNiCr (1 and 3 wt.% B4C) coatings, as evidenced by detected peaks corresponding to amorphous carbon and peaks indicating the stretching of C-B-C chains. The mechanical characterization of the FeNiCr-B4C coatings specified that additions of 1 and 3 wt.% B4C resulted in a notable increase in microhardness of 16% and 38%, respectively, with a slight decrease in ductility of 4% and 10%, respectively, compared to the B4C-free FeNiCr coating. Thus, the B4C addition can be considered a promising method for strengthening laser-cladded MEA FeNiCr-B4C coatings.

Signatures of superconductivity near 80 K in a nickelate under high pressure.

Although high-transition-temperature (high-Tc) superconductivity in cuprates has been known for more than three decades, the underlying mechanism remains unknown1-4. Cuprates are the only unconventional superconductors that exhibit bulk superconductivity with Tc above the liquid-nitrogen boiling temperature of 77 K. Here we observe that high-pressure resistance and mutual inductive magnetic susceptibility measurements showed signatures of superconductivity in single crystals of La3Ni2O7 with maximum Tc of 80 K at pressures between 14.0 GPa and 43.5 GPa. The superconducting phase under high pressure has an orthorhombic structure of Fmmm space group with the [Formula: see text] and [Formula: see text] orbitals of Ni cations strongly mixing with oxygen 2p orbitals. Our density functional theory calculations indicate that the superconductivity emerges coincidently with the metallization of the σ-bonding bands under the Fermi level, consisting of the [Formula: see text] orbitals with the apical oxygen ions connecting the Ni-O bilayers. Thus, our discoveries provide not only important clues for the high-Tc superconductivity in this Ruddlesden-Popper double-layered perovskite nickelates but also a previously unknown family of compounds to investigate the high-Tc superconductivity mechanism.

Biosynthesis, Spectrophotometric Follow-Up, Characterization, and Variable Antimicrobial Activities of Ag Nanoparticles Prepared by Edible Macrofungi.

The biosynthesis of silver nanoparticles (Ag NPs) could play a significant role in the development of commercial antimicrobials. Herein, the biosynthesis of Ag NPs was studied using the edible mushroom Pleurotus floridanus, and following its formation, spectrophotometry was used to detect the best mushroom content, pH, temperature, and silver concentration. After that, the morphology was described via transmission electron microscopy (TEM), and nanoscale-size particles were found ranging from 11 to 13 nm. The best conditions of Ag content and pH were found at 1.0 mM and 11.0, respectively. In addition, the best mushroom extract concentration was found at 30 g/L. According to XRD analysis, the crystal structure of the formed amorphous Ag NPs is cubic with a space group of fm-3m and a space group number of 225. After that, the function groups at the surface of the prepared Ag NPs were studied via FTIR analysis, which indicated the presence of C=O, C-H, and O-H groups. These groups could indicate the presence of mushroom traces in the Ag NPs, which was confirmed via the amorphous characteristics of Ag NPs from the XRD analysis. The prepared Ag NPs have a high impact against different microorganisms, which could be attributed to the ability of Ag NPs to penetrate the cell bacterial wall.

Structural and optical properties of Zn-implanted silica: effect of fluence and annealing

The phase-structural composition of silica films grown on Si substrates implanted with different fluences of Zn ions has been studied using transmission electron microscopy (TEM) and electron diffraction. Small clusters (2–3 nm) and larger clusters (5–7 nm) were formed in the as-implanted silica films with Zn concentration of 6–8 at % and 16%–18%, respectively. Furnace annealing at 750 °С for two hours in air resulted in the formation of an orthorhombic Zn2SiO4 phase (space group R-3) in the case of low fluence (5 × 1016 cm−2) and in the formation of a zinc blended ZnO phase (space group F-43m) in the case of high fluence (1 × 1017 cm−2). Based on the Rutherford backscattering spectrometry (RBS) data, it has been shown that impurity losses during implantation and subsequent annealing increase with the fluence of the implanted ions. The photoluminescence data were consistent with the TEM and RBS.

The La+3-, Nd+3-, Bi+3-Doped Ceria as Mixed Conductor Materials for Conventional and Single-Component Solid Oxide Fuel Cells

Clean energy devices are essential in today’s environment to combat climate change and work towards sustainable development. In this paper, the potential materials A2Ce2O7−δ (A = La+3, Nd+3, Bi+3) were analyzed for clean energy devices, specifically for conventional and single-component solid oxide fuel cells (SC-SOFCs). The wet chemical route has been followed for the preparation of samples. X-ray diffraction patterns showed that all three samples exhibited a defected fluorite cubic structure. It also revealed the presence of dopants in the ceria, which was confirmed by the fingerprint region of FTIR. The optical behavior, fuel cell performance and electrochemical behavior were studied by UV–vis, fuel cell testing apparatus and EIS, respectively. The SEM results showed that all samples had irregular polygons. In Raman spectra, the F2g mode corresponding to the space group (Fm3m) confirms the fluorite structure. The Raman spectra showed that A2Ce2O7−δ (A = La+3, Nd+3, Bi+3) have different trends. The conventional fuel cell performance showed that the maximum power density of Bi2Ce2O7 was 0.65 Wcm−2 at 600 °C. The performance of A2Ce2O7−δ (A = La3+, Nd3+, Bi3+) as a single-component fuel cell revealed that Nd2Ce2O7−δ is the best choice with semiconductors conductors ZnO and NCAL. The highest power density (Pmax) of the Nd2Ce2O7/ZnO was 0.58 Wcm−2, while the maximum power output (Pmax) of the Nd2Ce2O7/NCAL was 0.348 Wcm−2 at 650 °C. All the samples showed good agreement with the ZnO as compared to NCAL for SC-SOFCs.

Structure, heat capacity and Raman spectra of Ba2MgWO6 single crystals grown in BaCl2-MgCl2 flux

We present a new method of Ba2MgWO6 single crystal synthesis that allows to grow larger crystals using a BaCl2 and MgCl2 flux. Difficulties to grow single crystals of a size suitable for macroscopic material property measurements caused the majority of characterisation being published on polycrystalline samples. Our single crystal diffraction and energy dispersive X-ray analysis confirmed high quality of synthesised samples. Heat capacity measurements from 300 K to 2 K do not show any phase transitions. However, Raman spectra measured down to 77 K contain additional weak peaks at all temperatures probed, which is in a contrast with only 4 Raman active modes expected from the crystal structure with the space group Fm3¯m. This calls for a more detailed study of potential symmetry breaking that could also influence the electronic properties of the material.