Fluorite Type Research Articles

Microplotter printing of planar solid electrolytes in the CeO2–Y2O3 system

The formation process for planar solid electrolytes in the CeO2-Y2O3 system has been studied using efficient, high-performance, high-resolution microplotter printing technology, using functional ink based on nanopowders (the average size of crystallites was 12–15 nm) of a similar composition obtained by programmed coprecipitation of metal hydroxides. The dependence of the microstructure of the oxide nanoparticles obtained and their crystal structure on yttrium concentration has been studied using a wide range of methods. According to X-ray diffraction (XRD), the nanopowders and coatings produced are single-phase, with a cubic crystal structure of the fluorite type, and the electronic state and content of cerium and yttrium in the printed coatings have been determined using X-ray photoelectron spectroscopy (XPS). The results of scanning electron (SEM) and atomic force microscopy (AFM) have shown that the coatings produced are homogeneous, they do not contain defects in the form of fractures and the height difference over an area of 1 µm2 is 30–45 nm. The local electrophysical characteristics of the oxide coatings produced (the work function of the coating surface, capacitance values, maps of the surface potential and capacitive contrast distribution over the surface) have been studied using Kelvin-probe force microscopy (KPFM) and scanning capacitive microscopy (SCM). Using impedance spectroscopy, the dependence of the electrophysical characteristics of printed planar solid electrolytes in the CeO2-Y2O3 system on yttrium content has been determined and the prospects of the technology developed for the manufacture of modern, intermediate-temperature, solid oxide fuel cells have been demonstrated.

Gd-Bi-M-Ce-O (M = Cu, Zr, Ni, Co, Mn) ceria-based solid solutions for low temperature CO oxidation

Ceria based solid solutions doped by Gd, Bi, and the third dopant were synthesized by the co-precipitation method with ultrasonic treatment, followed by calcination at the temperature of 500°С. Characterization of the synthesized nanosystems by XRD, TEM, TG, Raman spectroscopy, FTIR, XPS was carried out. It is shown that all obtained powders of solid solutions crystallized into a cubic structure of the fluorite type, with an average particle size of 5–15 nm. The samples had a mesoporous structure of the pore diameter of 2–5 nm. The catalytic activity of Gd-Bi-M-Ce-O (M = Cu, Zr, Ni, Co, Mn) solid solutions was carried out. The catalyst Gd0.05Bi0.15Mn0.20Ce0.60O2 has the lowest oxidation temperature.

Feasibility Synthesis and Characterisation of Gadolinia Doped Ceria Coatings Obtained By Cathodic Arc Evaporation

The SOFC/SOEC community is now convinced that it is necessary to reduce the operating temperature of fuel cells to make the systems more robust, more reliable and thus to consider large-scale development. At the material level, the change of the reference electrolyte (YSZ) by a cerium compounds allows a significant performance gain for lower temperatures of use. It is obviously necessary to keep in mind the constraints related to the electrolyte application in solid electrolyte device, namely: good ionic conductivity unlike the electrical conductivity which must be low, electrochemical compatibility with the electrodes, be dense and covering on porous substrates.In this study, Gadolinia doped ceria coatings were deposited by cathodic arc evaporation from a metallic Ce-Gd (90/10 at%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon-oxygen gas mixture. The structural and chemical features of these films were determined by X-ray diffraction and scanning electron microscopy. Their electrical properties were characterised using impedance spectroscopy measurements. It is shown that the as-deposited coatings crystallise in the fluorite type fcc structure of ceria and that their composition is the same than that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation (figure1) and the activation energy is slightly higher than that given in the literature data for the bulk material.Figure 1 : Nyquist impedance plots of GDC coating, registered at 400°C, for two a.c. signal amplitudes. Logarithms of frequencies are indicated in the figure. Figure 1

STRUCTURE OF ISOTHERMAL SECTIONS OF THE DIAGRAM OF THE STATE OF THE SYSTEM ZrO2 – La2O3 – Eu2O3 AT TEMPERATURES 1500 AND 1250 °C

Using the methods of X-ray phase and microstructural analyzes, phase equilibria and structural transformations in the ZrO2 – La2O3 – Eu2O3 system at temperatures of 1500 and 1250 ºC in the whole range of concentrations were studied. Based on the obtained data, the corresponding isothermal cross sections are constructed. It is established that the fields of solid solutions are formed in the system on the basis of cubic (F) modification with fluorite type structure, tetragonal (T) modification ZrO2, monoclinic (B) and cubic (C) modifications Eu2O3, hexagonal (A) modification La2O3, as well as ordered phases with a structure of the pyrochlor type Ln2Zr2O7 (Py). The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. It was found that in the region with a high content of ZrO2 solid solutions are formed on the basis of tetragonal modification of ZrO2. The solubility of La2O3 in T-ZrO2is small and is ∼ 0.5% (mol.), which is confirmed by X-ray phase analysis and microstructural studies. It is established that at 1500 and 1250°C a continuous series of solid solutions is formed on the basis of an ordered phase of pyrochlor (Py) type Ln2Zr2O7. With decreasing temperature, the region of homogeneity of the specified solid solution narrows. Isothermal cross sections of the state diagram of the ZrO2-La2O3-Eu2O3 system at 1500 and 1250°C have a similar structure, although they are characterized by some differences due to the structure of the limiting binary systems. No new phases in the ternary system ZrO2 – La2O3 – Eu2O3 were detected at the studied temperatures.

Defect fluorite type phase in anion deficient rare earth zirconates, RE3Zr0.5Nb0.5O6.75 (RE = Nd, Sm, Gd, Dy, Y): Synthesis and electrical properties

Defect fluorite type phase in anion deficient rare earth zirconate compositions RE3Zr0.5Nb0.5O6.75 (RE ​= ​Nd, Sm, Gd, Dy, Y) were developed via the conventional solid state reaction route. The effects of anion deficiency on the crystalline structure and electrical properties of the compositions were analysed using powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and impedance spectroscopy techniques. Unusually, all the developed rare earth zirconates crystallise into a defect fluorite type structure with a space group Fm3m. The lattice parameter increases with the increase of the ionic radius of the lanthanide element present in the system following Vegard’s law. Raman spectra analysis further surmises the defect fluorite phase formation with some disorder from Nd to Y. The Cole Cole plot of the samples with temperature suggests non Debye type of relaxation process with an increase in conductivity through thermal activation of the charge carriers. The modulus spectrum analysis confirms the increased cooperative behaviour of the oxide ions from Nd to Y with a decrease in the lattice volume. This results in increased activation energy for long range conduction leading to a reduction in conductivity in the system. The composition, Nd3Zr0.5Nb0.5O6.75, exhibits maximum conductivity (4.29 ​× ​10-4 ​S/cm) at 1023 ​K, which shows less co-operative behaviour effects on the oxide ions due high lattice volume. Thus the present study demonstrates that creating oxygen vacancies in the system is not prime importance as cooperative behaviour among the ions increases and suppresses the conductivity more with contracted lattice volume.

The occurrence characteristics and recovery potential of middle-heavy rare earth elements in the Bayan Obo deposit, Northern China

The Bayan Obo deposit is a world-class Fe-REE-Nb deposit, and its reserves of rare earth element (REE) resources rank the first over the world. In the face of the current situation of insufficient utilization rate of rare earth resources and scarcity of middle-heavy rare earth elements (M−HREE) resources, the Bayan Obo deposit with such a huge amount of M−HREE cannot be underestimated. In this paper, the occurrence characteristics of M−HREE in different types of iron ore in the Bayan Obo main ore body are studied by using field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and advanced mineral identification and characterisation system (AMICS), and the enrichment mechanism is also discussed. The results show that both Sm and Y are the most abundant M−HREE in each type of iron ore in the main ore body, and the content of M−HREE accounts for 1.41%–5.57% of total REE, among which the content of M−HREE in aegirine type Nb-REE-Fe ore (824.47 ppm) and fluorite type Nb-REE-Fe ore (794.82 ppm) are higher, and the content of M−HREE in massive type Nb-REE-Fe ore is lower (318.49 ppm). The main minerals containing M−HREE are bastnasite, parisite, Huanghoite, monazite, aeschynite and fergusonite, among which the content of M−HREE in fergusonite and aeschynite are the highest. According to the characteristics of mineral paragenetic association of REE in this ore district, it is believed that the REE migrates mainly in many different forms of complexes. Heavy rare earth elements (HREE) mainly experienced carbonatite magmatism stage, sodium-fluorine metasomatism stage and late vein mineralization stage, and finally got enrichment.

CeO2 thin film supported on TiO2 porous ceramics

The work demonstrates an easy and simple method for obtaining a TiO2 porous ceramic coated with a CeO2 thin film (COTF) on the surface. Replica technique used a 30 PPI polyurethane sponge and TiO2 ceramic suspension. Dip coating technique was used to coat the material surface and cerium polymeric resin synthesis was obtained by polymeric precursors method. Thermal analysis indicated a thermostable material from 500 °C. X-ray diffraction analysis of calcined CeO2, at 600 to 900 °C, resulted in monophasic and crystalline with a fluorite type cubic structure. Scanning electron microscopy made it possible to monitor COTF formation and growth from islands shape to a more homogenous form over 10 depositions.

Control of defect formation and ordering in Eu3+ doped RE2Ce2O7 (RE = La, Y, and Gd) red phosphor

The control of defect formation and ordering in the lattice on the photoluminescence properties of Eu3+ doped RE2Ce2O7 is studied by the incorporation of some rare earth elements (RE = Y, La, Gd) in the system. Structural studies divulge all the compositions to crystallize into a fluorite type structure with the space group Fm3m. Raman mode analysis supplements the confirmation of the fluorite structure and further indicates an oxygen vacancy ordering in the lattice from Y to Gd. The defect formation of Ce3+ concentration from the x-ray photoelectron spectroscopy analysis shows dependence on the type of rare earths. The ordering in the lattice is associated more with the trapping/repelling of oxygen vacancy based on the rare earth. In other words, the defect formation is minimum for Gd by trapping more oxygen vacancies and maximum for the Y system due to more disorders in the lattice. The Ce3+ concentration and the ordering greatly affected the absorbance and luminescence properties. Thus, the Gd system with more ordering and less defect formation exhibited enhanced red emission of Eu3+ (612 nm), which is more than 1.8 times that of La based phosphors and 11 times better than Ce0.9O2:0.1Eu3+. Also, studies on the effect of Eu3+ concentration in the Gd2−xCe2O7:xEu3+ system indicated further improvements in the red emission intensity along with a high asymmetric ratio, good chromaticity coordinates (0.66, 0.35), and high color purity (97.6%). This study demonstrates that the role of ordering associated with defect formation plays significantly in determining the luminescence properties.

Photocatalytic degradation of methylene blue dye by fluorite type Fe2Zr2-xWxO7 system under visible light irradiation.

Nano-sized Fe2Zr2-xWxO7 system was prepared using the Pacini method where x=0, 0.05, 0.1 and 0.15. All the samples were characterized using chemical analysis, X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), transmission electron microscopy (TEM), UV-vis diffuse reflectance measurements (DRS) and surface area measurements. The undoped Fe2Zr2O7 was crystallised in the cubic fluorite phase as a major phase in addition to rhombohedral phase of Fe2O3 and monoclinic phase of ZrO2 as the minor phases. Meanwhile, single cubic fluorite phase was defined for Fe2Zr0.85W0.15O7 sample. The last has the lowest band gap (1.69eV) and the highest surface area (106m2/g). From TEM, the average particle size of the prepared samples was in the range of (3-7nm). The photocatalytic efficiency of the prepared Fe2Zr2-xWxO7 system was manifested by the degradation of methylene blue and real textile wastewater of blue colour. Ascending degradation efficiency was exhibited with increasing tungsten concentration which is in accordance with their band gap as well as their surface area values. The degradation rate using Fe2Zr0.85W0.15O7 sample obeys the pseudo-first order kinetic at the optimum degradation conditions (1.5g/L catalyst and pH11). Fe2Zr0.85W0.15O7 showed promising photocatalytic activity for real textile wastewater where the 69% COD removal was obtained under the same conditions used for methylene blue degradation.

Study of the structure of mixed Zr-Y-O and Zr-Y-Mg-O oxides by XRD and XAFS methods

A comparative study was carried out of the structure of samples of zirconium oxides modified by yttrium and magnesium, synthesized by coprecipitation and calcined during 10 days at a temperature of 1250 °C. Refinement of the structure of the samples according to diffraction data within the framework of the fluorite type, gives high uncertainty factors, regardless of composition, and variation of structural parameters does not reduce their value. EXAFS analysis of the local structure of the samples revealed separate clusters consisting only of yttrium and oxygen ions in the structure of both samples. It has been suggested that the presence of these clusters prevents refinement of structures using the model of statistical solid solution with a fluorite structure.

Жидкофазный синтез и исследование физико-химических свойств керамических электролитных наноматериалов в системе CeO2 – Sm2O3 для твердооксидных топливных элементов

By the method of joint crystallization of solutions of nitrate salts, the highly dispersed powders of the composition (CeO2)0.98(Sm2O3)0.02, (CeO2)0.95(Sm2O3)0.05, and (CeO2)0.90(Sm2O3)0.10 are synthesized, and on their basis, nanoceramic materials with a crystalline cubic structure of fluorite type are obtained, with the grain size of the crystallites of ~68–81 nm (1300°С). Their mechanical and electrophysical properties are studied; it is found that they have an open porosity of 2–6% and predominantly ionic (ti = 0.82–0.71 in the range of 300–700°C) type of electrical conductivity due to the formation of mobile oxygen vacancies during the heterovalent replacement of Се4+ with Sm3+, σ700°C =1.3 × 10–2 S/cm. The studies show the prospects of using the obtained ceramic materials as solid oxide electrolytes of intermediate-temperature fuel cells.

Studies on structural, morphological, and electrical properties of Ga3+ and Cu2+ co-doped ceria ceramics as solid electrolyte for IT-SOFCs

The present study highlights the effect of Ga3+ and Cu2+ co-doping on the crystal structure, surface morphology and ionic conductivity of ceria ceramics in the system Ce0.8Ga0.2-xCuxO2-δ for potential applications as the solid electrolyte material in the intermediate temperature solid oxide fuel cells (IT-SOFCs). Ultrafine Ce0.8Ga0.2-xCuxO2-δ (for x = 0, 0.05, 0.1, 0.15, and 0.2) nanopowders were prepared via glycine nitrate auto-combustion method. Phase identification, microstructural, and ionic conductivity of all the ceria ceramics were observed by powder XRD, SEM, TEM, and impedance analyses, respectively. Rietveld structural analysis using powder XRD pattern for all the co-doped systems confirms cubic fluorite type structure having Fm-3m space group, similar to cerium oxide. All these samples were found to have density above 85% after sintering at 1300 °C for 4 h. Raman spectra revealed the oxygen vacancies in all the compositions. Thermal analysis for change in weight and thermal expansion coefficient with temperature were performed by TGA and high temperature XRD measurements, respectively. Thermal expansion coefficient of the developed electrolytes matches with the commonly used electrode materials. The composition Ce0.8Ga0.05Cu0·15O1.825 was found to demonstrate the maximum ionic conductivity with the least activation energy among all the existing co-doped ceria ceramics. These features make it a promising candidate in the IT-SOFC as the electrolyte material.

YHO, an Air-Stable Ionic Hydride.

Metal hydride oxides are an emerging field in solid-state research. While some lanthanide hydride oxides (LnHO) were known, YHO has only been found in thin films so far. Yttrium hydride oxide, YHO, can be synthesized as bulk samples by a reaction of Y2O3 with hydrides (YH3, CaH2), by a reaction of YH3 with CaO, or by a metathesis of YOF with LiH or NaH. X-ray and neutron powder diffraction reveal an anti-LiMgN type structure for YHO (Pnma, a = 7.5367(3) Å, b = 3.7578(2) Å, and c = 5.3249(3) Å) and YDO (Pnma, a = 7.5309(3) Å, b = 3.75349(13) Å, and c = 5.3192(2) Å); in other words, a distorted fluorite type with ordered hydride and oxide anions was observed. Bond lengths (average 2.267 Å (Y-O), 2.352 Å (Y-H), 2.363 Å (Y-D), >2.4 Å (H-H and D-D), >2.6 Å (H-O and D-O), and >2.8 Å (O-O)) and quantum-mechanical calculations on density functional theory level (band gap 2.8 eV) suggest yttrium hydride oxide to be a semiconductor and to have considerable ionic bonding character. Nonetheless, YHO exhibits a surprising stability in air. An in situ X-ray diffraction experiment shows that decomposition of YHO to Y2O3 starts at only above 500 K and is still not complete after 14 h of heating to a final temperature of 1000 K. YHO hydrolyzes in water very slowly. The inertness of YHO in air is very beneficial for its potential use as a functional material.

TEM characterization of high burnup fast-reactor MOX fuel

This work examines the radial evolution of a high burnup fast reactor mixed-oxide (MOX) fuel pellet irradiated at the Fast Flux Test Facility (FFTF) using scanning (SEM) and transmission electron microscopy (TEM). At 21.3% fissions per initial metal atoms (FIMA), the sample analyzed in this work is likely among the highest burnup oxide fuel samples ever evaluated using TEM. Initial SEM examination focused on the characterization of the fuel microstructure and solid fission product behavior as a function of radial position. The fuel pellet underwent extensive restructuring as demonstrated by columnar grain formation near the central void. Oxide fission product phases were confined to near the fuel centerline and decomposed from perovskite BaZrO3 to the fluorite ZrO2 type crystal structure. Metallic five metal precipitates (FMPs) were observed at all radial positions and the Pd-rich metallic phase increased in area fraction moving toward the pellet surface. TEM examination focused on the determination of dislocation density ranging from the fuel pellet center to the pellet surface. Dislocation density was highest in the cooler regions of the fuel pellet, with the outer edge experiencing grain refinement and high defect concentrations consistent with the rim structure. The results of the paper highlight the variable dislocation behavior as a function of radial position in high burnup MOX fuels, as well as describe the largely unexplored change in crystal structure of the oxide solid fission product phase.

Effect of burnup on the mechanical properties of doped UO2 ceramic pellets using the simfuel technique

To determine the mechanical properties varying with burnup, the simulated 10 wt% ZrO2-doped UO2 ceramic pellets with burnups ranging from 0 to 250 GW d/tU were prepared by pressureless sintering in a hydrogen reducing environment. Mechanical properties such as hardness, elastic modulus and fracture toughness, as well as microstructures of the simulated pellet samples with different burnups (0, 75, 150 and 250 GW d/tU, respectively) were characterized by Vickers micro-indentation technique, X-ray diffraction, scanning electron microscopy and electron probe X-ray microanalysis, respectively. Results show that the relative densities of the simulated pellet pellets are between 93.5% and 95% and the measured elemental compositions are similar to the expected values. There are three distinct phases in the simulated 10 wt% ZrO2-doped UO2 fuel pellet samples, i.e., the matrix phase with the fluorite type structure, the oxide phase with perovskite type structure, and the metallic ε-phase. The lattice parameter of the simulated 10 wt% ZrO2-doped UO2 fuels gradually decreases with the increase of burnup. The hardness, elastic modulus and fracture toughness of simulated 10 wt% ZrO2-doped UO2 ceramic fuel pellets are significantly decreased by approximately 38.7%, 29.5% and 13.5% when the burnup increases from 0 to 250 GW d/tU, respectively.

Design of Active Site at Heterointerface between Brownmillerite Type Oxide Promoter and Fluorite Cubic ZrO2 in Anode of Intermediate Temperature SOFCs

New hopping site for mobile oxygen (i.e., active site) on cubic ZrO2 surface in the anode was designed along the guide of previously published first-principles simulation. To design it, the authors proposed a heterointerface between brownmillerite type oxide and fluorite type cubic ZrO2 (“BF heterointerface”) as model active site. Small amount (0.2 wt %) of brownmillerite type oxide promoter made new hopping site on YSZ and conspicuously improved both anode performance and its stability at 700 °C. The combination work of XPS analysis and surface atomistic simulation suggests the formation of Frenkel type defect clusters on BF heterointerface. Also, this combination work was useful to conclude why the optimum content of brownmillerite type oxide for promotion of anode reaction was around 0.2 wt %. Finally, it is found that “BF heterointerface” designed by combination of the modeling, surface microanalysis, and fabrication can solve the trade-off relation between high anode performance and its long-time sta...

Ab initio analysis of the optical spectra and EPR parameters of Ni2+ ions in CaF2 and CdF2 crystals

Crystals with fluorite type structure doped with transition metals (TM) in different oxidation states provide the possibility of investigating optical spectra, magnetic properties and ligand field (LF) parameters of TM in cubic eightfold coordination. If the doped ion in the host crystal matrix has a degenerate ground state then, due to the strong T⊗τ Jahn-Teller (JT) effect, the cubic coordination geometry of the impurity ion will be distorted to octahedral, with the change in its properties. In this paper we present the results of the ab initio investigation of absorption optical spectra, JT stabilization energy in the ground state, spin-Hamiltonian and ligand field parameters of divalent nickel ion doped in cubic CaF2 and CdF2 crystals. The analysis of new cluster [NiF6]4- with trigonal symmetry (D3d) at the Ni2+site was made based on the ab initio multireference methods (MR). All calculations are applied to the [NiF6]4- cluster embedded in an extended point charge field of host matrix ions built according to the Gellé-Lepetit procedure. After density functional theory (DFT) optimization of the doped crystals, the ab initio energy calculation of the electronic states and corresponding wave functions of Ni2+ ions is performed from the complete active space self-consistent field (CASSCF). The improved energy states obtained by using different approaches such as N-electron valence second order perturbation theory (NEVPT2), second order dynamic correlation dressed complete active space (DCD-CAS2), difference dedicate configuration interaction with three degrees of freedom (MRDDCI3) and spectroscopy-oriented configuration interactions (SORCI), were analyzed. In addition, the ab initio ligand field theory (AILFT) procedure allows extracting all LF parameters and spin-orbit coupling constant. The obtained results are discussed and the comparison with the available in the literature corresponding experimental values literature yields a reasonably agreement between theory and experiment, which justifies this new route of investigation.The structural mechanism around Ni2+ center through JT effect, combined with the above mentioned methodology, allows for more consistent and reliable calculations of optical spectra and spin-Hamiltonian parameters of any impurity ions doped in eightfold cubic coordination.

Fast and continuous obtaining of Eu3+ doped CeO2 microspheres by ultrasonic spray pyrolysis: characterization and photocatalytic activity

In this work, CeO2:xEu3+ (x = 0, 0.01, 0.02, 0.04 and 0.08 mol%) microspheres were obtained by the fast and continuous ultrasonic spray pyrolysis method. Powders were characterized by X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), scanning electronic microscopy (FESEM), Raman spectra, UV–Visible spectroscopy (UV–Vis) and photocatalytic activity. All XRD patterns were indexed by the cubic structure of the fluorite type, without the presence of secondary phases, indicating success in the Eu3+ doping in the CeO2 structure. In addition, The XRF analysis confirmed the presence of Eu in the CeO2 powders. In the Raman spectra of the samples occurs the vibrational mode F2g, which is a characteristic band of materials with the fluorite type structure. Moreover, as the Eu3+ ion increased, it was noticed the appearance of additional bands referring to oxygen vacancies. FESEM showed that the CeO2:xEu3+ particles have a spherical morphology with homogeneous chemical composition and particle size between 73 and 1560 nm. It can be seen a slight increase of defects in their morphology as the Eu3+ ion increases. The band gap varies between 3.22 and 3.28 eV, being influenced by defects in oxygen vacancies and the concentration of Ce3+ ion. The addition of Eu3+ generates the introduction of intermediary levels in the conduction band of CeO2, besides increasing the reactive species effects, favoring the photocatalysis of Rhodamine B dye.

Crystal phase and surface defect driven synthesis of Pb1−xSnxF2 solid solution electrolyte for fluoride ion batteries

Pb1−xSnxF2 layered fluoride super-ionic conductors have become of increased interest for its potential use for all-solid-state secondary fluoride-ion based batteries. By planetary high-energy ball-milling, we have prepared solid-solutions for different stoichiometries: x=0.4–0.6. These materials were investigated by X-ray Diffraction (XRD), Electrochemical Impedance Spectroscopy (EIS), Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmission Electron Microscope (HRTEM) and Nuclear Magnetic Resonance (NMR) from which a dominant γ-phase (β-PbF2 form) cubic structure with crystal and surface defects have been revealed. Crystallite sizes of around 17nm were achieved. The ionic conductivity of the materials provided a maximum for x=0.45 reaching a value of 2.5·10−3S·cm−1 at room temperature, with an activation energy of 0.30eV. This solid-state fluorite type electrolyte was applied for testing a solid fluoride ion battery assembly consisting of Bi-cathode and CeF3-anode.

On the homogeneity of high entropy oxides: An investigation at the atomic scale

Homogeneous distribution of the constituent elements at the atomic scale in high entropy oxides (HEOs) was demonstrated for the first time by atom probe tomography (APT). Three different single-phase HEOs having rocksalt, fluorite, and perovskite type crystal structures were synthesized using nebulized spray pyrolysis process. The as-synthesized powders were compacted into pellets under high pressure of 6 GPa. Both as-synthesized and compacted powders were investigated by X-ray diffraction and transmission electron microscopy. APT results showed that the constituent cations in all three HEO systems were homogenously distributed with no significant segregation or concentration fluctuation even at the atomic scale.