Fluorite Type Research Articles

Synthesis and characterization of the RE2A2O7 oxides with an ultrahigh-entropy sublattice occupied by rare-earth elements

The possibility of fabricating novel high-entropy oxides (HEOs) with one ultrahigh-entropy sublattice consisting of 13 cations in RE2A2O7 (RE = [La, Sm, Nd, Gd, Dy, Yb, Y, Er, Eu, Tb, Ho, Lu, Tm], A = Zr, Hf, Ti, Sn, Ce or Pr) is demonstrated. All the samples exhibited a pure pyrochlore-type or defective fluorite crystalline structure with various degrees of cation disordering. Particularly, RE2Ti2O7 and RE2Sn2O7 exhibited a pure pyrochlore-type structure with high degree of ordering, while RE2Ce2O7 and RE2Pr2O7 demonstrated a single fluorite type HEO structure. The results pave the way to fabricate RE2A2O7 HEOs with an ultrahigh-entropy sublattice and potential application as the ceramic layer in thermal barrier coatings.

Anticancer Activity of Green Synthesized Manganese Doped Cerium Oxide Nanoparticles Prepared by Using Acacia Concinna Fruit Extract

AbstractPure CeO2 and Ce1‐xMnxO2, where x = 0, 2, 4 and 6% w/w, were synthesized by sol‐gel method using Acacia Concinna fruit extract as a surfactant and stabilizing agent. The synthesized particles were subjected to various characterization techniques, including XRD, HRTEM, FESEM, FTIR, Raman and UV‐Visible spectroscopy. The XRD pattern of the samples demonstrated single phase of CeO2, with cubic fluorite type structure and crystallite size of 6–7 nm. The morphology of the nanoparticles (NPs) was analyzed by FESEM and HRTEM which illustrated an aggregate of irregular spherical nanoparticles and the average particle size is around 18 nm. Raman spectroscopy validated the phase purity and indicated about the structural defects caused by the dopants. The bandgap energy of CeO2 NPs is calculated to be 3.00 eV from the Tauc plot of UV‐Visible spectroscopy, which gradually decreased to 2.43 eV with increase in manganese doping. Cytotoxicity studies signified the role of Mn‐doped CeO2 NPs as a potential nanotherapeutic agent for cancer treatment. The cell viability assay showed that 200 µg/mL of 6% Mn‐doped CeO2 nanoparticles exhibited remarkable cytotoxic effect by inhibiting 50% of cancer cells both in breast and colon cancer cell lines without affecting the healthy cell lines.

Navigating the 18-n+m Isomers of PdSn2: Chemical Pressure Relief through Isolobal Bonds and Main Group Clustering.

The 18-n electron-counting rule provides structural guidelines for electronically feasible transition metal (T)-main group (E) phases, contributing toward the goal of material design. However, the availability of numerous potential structure types at any electron count creates a challenge for the prediction of the preferred structures of specific compounds, as is illustrated by the concept of 18-n+m isomerism. In this Article, we explore the driving forces stabilizing one 18-n+m isomer over another with an analysis of the structure of PdSn2, a layered intergrowth of the fluorite and CuAl2 structure types. The DFT-reversed approximation Molecular Orbital (DFT-raMO) method reveals that PdSn2 and its hypothetical parent structures all adhere to bonding schemes approximating the electronic configurations expected from the 18-n rule, with various degrees of isolobal Pd-Pd bonding and Sn clustering. However, partial electron transfer between the Pd 5p orbitals to the Sn 5s orbitals contributes to the absence of convincing electronic pseudogaps near their Fermi energies. As such, there is no clear electronically driven preference among the structure types. This situation allows for atomic packing effects to prevail: DFT-Chemical Pressure (DFT-CP) analysis illustrates that in the fluorite-type parent structure, positive Pd-Sn CPs lead to overcompression of the Pd atoms and a stretching of the relatively open Sn sublattice. In contrast, in the CuAl2-type parent structure, Sn atoms cluster into tetrahedra, opening space for an expanded Pd environment and the formation of Pd-Pd interactions. However, the tetrahedral packing of the Sn atoms here leads to frustration between negative and positive Sn-Sn CPs. Through the development of the angular CP correlation function (CPcor+) as a tool to quantify frustration among interatomic interactions, we demonstrate how the observed PdSn2 structure balances these effects by tuning the degree of Sn-Sn clustering and expansion of the Pd environment. These observations point to generalizations for most 18-n+m isomers, where increased main group ligand clustering (+m) and isolobal bonds (+n) can accommodate compositions with different T and E atomic sizes.

A case study of the Yanshanian fluorite mineralization in South China: Fluid inclusion, element and isotope geochemistry and zircon U-Pb geochronology of the Kantian fluorite deposit in southern Jiangxi Province

The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H2O, with minor C3H6. Isotope analysis indicated δDVSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18OVSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H2O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit.

High temperature nanoindentation of (U,Ce)O2 compounds

Continuing to refine our knowledge of the evolving mechanical properties of nuclear fuel over the entire fuel service cycle is necessary to understand the pellet-clad mechanical interaction that occurs in the fuel rods during the operation. A challenge with measuring the mechanical properties of irradiated fuels is their high levels of radioactivity that usually require the use of hot cells making testing time consuming and expensive. Nanoindentation based techniques can be employed on minute volumes of material to measure mechanical properties, including Young’s modulus, hardness, and creep stress exponents. Increasing the mixed oxide fuels mechanical properties database through a variety of testing techniques should enhance modelers’ abilities to predict failure mechanisms in the fuel/clad interface. A current challenge to testing mixed oxide fuels is the plutonium component in the fuel. Mixed fluorite type oxides with ceria (CeO2) can be used as a surrogate for mixed oxide fuels. In this study, (U,Ce)O2 solid solutions samples are used to develop elevated temperature nanoindentation and nanoindentation creep testing methods for use on mixed oxide fuels. Nanoindentation testing was performed on 3 separate (Ux-1,Cex)O2 compounds ranging from x equals 0.1 to 0.3 in equal steps at temperatures up to 800 °C: their Young’s modulus, hardness, and creep stress exponents were evaluated. The Young’s modulus decreases in the expected linear manner while the hardness decreases in the expected exponential manner. The nanoindentation creep experiments at 800 °C give stress exponent values, n = 4.7–6.9, that suggests dislocation motion as the deformation mechanism.

Principal component analysis of mineral and element composition of ores from the Bayan Obo Nb-Fe-REE deposit: Implication for mineralization process and ore classification

The Bayan Obo Nb-Fe-REE polymetallic deposit in northern China is the world’s largest light REE deposit. The deposit was formed through multiperiodic alteration and mineralization, and thus mineral species and assemblages are extremely complex. To date, there is still no consensus on the classification of ore types, and research on the paragenetic association of minerals is still inadequate. Eighty ore samples are divided into seven types according to altered minerals, including dolomite, iron oxide, aegirine, riebeckite, biotite, fluorite, and barite types. These samples were analyzed by a TESCAN Integrated Mineral Analyzer (TIMA) for their mineral and element composition. The data set was investigated by principal component analysis (PCA) to reveal the mineralization and alteration information and classify the ores.PCM1 to PCM3 and PCE1 to PCE3 represent the first three principal components for PCA results of minerals and elements, respectively. The results indicate that PCM1 may distinguish rare earth mineralization from barite and silicification alteration that is associated with the latest fluids. PCM2 can distinguish mineralization and alteration associated with Nb from those associated with REE. The combination of PCM2 and PCE1 indicates that the precipitation of REE may be closely related to fluorination and phosphate, while the combination of PCM2 and PCE3 indicates that the Nb mineralization may be more closely related to alteration of riebeckite and biotite, as well as to Ti-rich fluids. In addition, PCM3 distinguishes the Th mineralization and associated fluorination from other alteration and mineralization. Based on PCA results, the above seven ore types can be classified into three types: dolomite REE ore, Fe-REE-F ore, and Nb-rich ore, which provides a simplified and comprehensive classification for Bayan Obo ores. PCA-based approach combining geochemical and mineralogical data can quickly identify ore types, which is helpful in mineral exploration.

(Invited) Oxide Ion Conductivity and Oxide Vacancy Diffusion Coefficient of Stabilized ZrO2 and Doped CeO2 Discussed Based on Classical Defect Chemistry with Particular Focus on Valence State (2+, 3+, and 4+) of Doped Cations

So far tremendous works have been reported on the oxide-ion conductivity of fluorite-type oxides typically stabilized zirconia and doped ceria. It is well known that the oxide-ion conductivity vs. dopant concentration plot shows maximum around 10 mol percent dopant concentration and the maximum conductivity varies with the dopant species. Interests tend to be focused on the higher and the stabler conductivity. For the aim, explorations are made on the dopant survey and the phase stability of the solid solution.Generally, conductivity is considered proportional to the product of carrier concentration and carrier mobility. For the fluorite-type oxide ion conductors, it is considered that carrier is oxygen vacancy, V O ··, and mobility is proportional to oxygen vacancy diffusion coefficient, DV . However, such defect chemical approach to the fluorite-type oxides is not popular. When we assume that the mobility is constant following the classical hypothesis, we cannot explain the conductivity maximum.The author has been trying to discuss the oxide-ion conduction in fluorite-type oxide solid solutions in terms of oxygen vacancy concentration, cV ,and DV .Using the literature data on conductivity and composition relationship, the author has already calculated DV for some compositions of stabilized zirconia and doped ceria as a function of composition. The data have been published in a short review [1] and books [2,3]. However, the published graphical displays were so crowded that the physical meanings seem still unclear.In this presentation, discussion is made on the conductivity of stabilized zirconia and doped ceria in the following order to make clear the characteristic feature of DV with the variation of valence state and chemical species of dopant oxides.1: zirconia base solid solutions 1a: with divalent cation oxides 1b: with trivalent cation oxides2: ceria base solid solutions 2a: with divalent cation oxides 2b: with trivalent cation oxides3: stabilized zirconia – ceria solid solutions 3a: stabilized zirconia base solid compositions 3b: ceria base solid compositions 3c: trivalent cerium formation by partial reductionIt is clarified that DV of fluorite type oxide is affected by the dopant cation not only by different valent but also by the same valent cations.

Effects of Bi2O3 doping on structural and electrical properties of Ce0.8Sm0.2O1.9 electrolyte for solid oxide fuel cells

The study investigates the impact of Bi2O3 doping on the crystal structure, density, and ionic conductivity of Ce0.8Sm0.2O1.9, a type of samarium-doped ceria oxide (SDC). The material is intended for use as a solid electrolyte in intermediate temperature solid oxide fuel cells (IT-SOFCs). The SDC-based electrolyte was created using the auto-combustion technique, with various molar ratios of Bi2O3. Phase compositions, microstructure, and ionic conductivity of all ceria ceramics were analysed using XRD, SEM and impedance analyses, respectively. The language is formal, clear, objective, and value-neutral, using high-level, standard language with consistent technical terms. Grammar, spelling, and punctuation are correct. Consistent citation and footnote style are maintained. The samples are single-phase ceramics that crystallise into a cubic fluorite type structure with space group Fm-3 m, as confirmed by the X-ray diffraction pattern. Technical abbreviations are explained. The structure ensures a logical flow of information with causal connections between statements. No filler words or biased language are used. SDC/Bi2O3 composite powders exhibit high sintering activity. The relative density of all samples sintered at 1300 ºC for 5 h was more than 96%, which is higher than that achieved by pure SDC electrolyte sintered at 1400 ºC (94.06%). Electrochemical performance results demonstrate that adding an appropriate amount of Bi2O3 can significantly enhance the conductivity of SDC materials. The SDC-based electrolyte containing 9 mol% of Bi2O3 (SDCB9) demonstrates the maximum conductivity of 43.5 mS·cm−1 at 800 °C, surpassing that of pure SDC which measures 26.86 mS·cm−1.

The defects of structural and phase transformations in polycrystalline cerium dioxide under heating in vacuum and in air

Structural changes in cerium dioxide, when heated in vacuum in the range of 25‒1600 °C, in air in the range of 25‒1500 °C, and during successive annealing in the range of 1600‒2100 °C in air, followed by quenching in water, were studied. In the crystal lattice of CeO2‒х, the F → F1 phase transformation in vacuum proceeds in the range of 1100‒1600 °C; additionally, at 1200 °C, X-ray lines of the C-type Ce2O3 phase appear. The thermal expansion coefficient of phases of the fluorite type F and F1 in the range of 25‒1500 °C in air, as well as phases of the fluorite type F, F1 and type C Ce2O3 in the range of 25‒1600 °C are determined in vacuum and their dependence on the change in the oxygen content in the CeO2‒х crystal lattice was found. The kinetic conditions for reduction of cerium dioxide in vacuum and oxidation in air are different. The cubic structure of the fluorite type F CeO2‒х, when the samples are heated in air, is preserved up to 1800 °C with the content of anionic vacancies, at 1900 °C the transformation F → F1 occurs. The formation of loops, edge and screw dislocations in the structure of cerium dioxide grains after annealing of samples in the range of 1900‒2100 °C in air were discovered for the first time. The decomposition of the structure F1 into cerium oxide phases of types F and C proceeds at 2100 °C along the height and boundaries of screw dislocations. It was found that fragments of the C-type phase of cerium oxide are located on loops along the height of screw dislocations, which indicates the movement and evaporation of these fragments. When the samples are oxidized at 1600 °C in air, the black-colored C Ce2O3‒х phase in a gradient of different concentrations moves along certain trajectories to opposite ones. grain boundaries, abuts against dislocation loops, bends them, and oxidizes to phases F1 and F. In the structure of polycrystalline cerium dioxide, when heated in vacuum and in air, certain concentrations of defects control phase transformations.

A novel defect fluorite type high-entropy (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 ceramic with low thermal conductivity and CTE: a mechanism study

The “seesaw relationship” between thermal conductivity and thermal expansion coefficient (CTE) in most high temperature ceramics has become an obstacle to the design of long-life multilayer thermal/environmental barrier coatings (T/EBC). Due to low thermal conductivity and CTE, defect fluorite type high-entropy rare earth (RE) hafnates have drawn a lot of interest for potential application in T/EBC systems. This work designs and synthesizes the (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 with comprehensive thermal performance and investigates the thermophysical mechanism from the phonon scale. In addition to the lattice distortion effect caused by the point defects of multicomponent substitutional atoms in (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7, the oxygen vacancies in the defect fluorite lattice also play a critical role in reducing the thermal conductivity. From microscopic thermal expansion behavior, the low-frequency optic phonons originated from the vibration of RE atoms are the key factors in altering CTE for hafnates. And doping smaller RE ions is beneficial for enhancing the RE–O bond strength and further reducing CTE. The results contribute to the understanding of high-entropy strategic design and suggest that (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 is a promising top layer material in the implementation of T/EBC.

Cation-heterogeneity in internally gelated U1-zCezO2-x, 0.15 ≤ z ≤ 0.3 microspheres

Internal gelation of aqueous mixtures of metal (M = Ln, An) nitrate with Uranyl Nitrate is generally assumed to yield cation homogeneity and a fluorite type single phase U1-zMzO2±x solid solution. As-sintered (U,Ce)O2 internally gelated microspheres, manufactured with target z values up to 0.3 using Ce(NO3)3, were observed to exhibit systematic peak broadening and splitting at higher 2θ angles in their X-Ray diffraction (XRD) patterns, correlating with increasing z≥0.15. This was interpreted as an unexpected departure from a single phase material. Thermogravimetry was used to make an initial assessment whether these peak anomalies were caused by an oxygen hypostoichiometry. Results indicated global oxygen stoichiometry for all compositions. The subsequent detailed characterization study via Electron Probe Micro Analysis of cross-sections of the as-sintered microspheres revealed the systematic presence of spherical Ce concentration gradients, as well as µm-sized highly Ce-enriched features. EDS and TEM studies on focused ion beam lamellae extracted from the cross-sections of as-sintered microspheres revealed a hexagonal Ce4.67(SiO4)3O minor phase manifesting as single grain precipitates and clusters uncovering the presence and critical role of Silicon as an unexpected contaminant and Ce-scavenger from surrounding (U,Ce)O2 grains. Characterization at intermediate heat treatment steps revealed that the systematic U/Ce heterogeneity features are already present post-gelation and are independent of the superimposed trace Ce-Si-O phase. This work constitutes the first systematic cation distribution study on cross-sections of (U,Ce)O2±x microspheres, executed on a series of compositions, using a combination of elemental mapping techniques.

Y doped La2Ce2O7 proton conducting SOFC electrolyte membrane: Thin film deposition via EPD, electrochemical performance and DRT analysis

Herein, a new series La2-xYxCe2O7 (x = 0, 0.05, 0.10, 0.15 and 0.20) as electrolyte materials are investigated for intermediate temperature SOFCs application. The adopted synthesis route for nano sized La2-xYxCe2O7 powder is glycine nitrate combustion. The crystal structure and phases present in the Y doped La2Ce2O7 is studied extensively using X-ray diffraction and Raman spectroscopy. The material exhibits dual phase fluorite (F) type and C type phases. The structural relationship along with oxygen vacancies are critically analyzed. The ionic conductivity of the Y doped La2Ce2O7 series are studied and La1.85Y0.15Ce2O7 exhibits the highest ionic conductivity of 3.29 × 10−3 Scm−1 in moist atmosphere at 700 °C. The stability and suspension chemistry of La1.85Y0.15Ce2O7 is investigated in different suspension media and then electrophoretic deposition (EPD) employed to fabricate the thin (∼13 μm) and dense electrolyte on the fuel electrode. The cell demonstrated a maximum power density (MPD) of roughly 500, 353.6, and 197 mW cm−2 at 700 °C, 650 °C, and 600 °C, respectively. The cell is found to be stable under constant operation of short-term stability test at 700 °C. The distribution of relaxation time (DRT) from the impedance spectra suggests that the gas diffusion process in the electrodes contributes greatly to the overall polarization of the cell.

Synthesis, structural, morphological and optical properties of environment friendly yellow inorganic pigment Bi4Zr3O12

This study reports on the structural, morphological, microstructural, electronic and optical properties of 5 nm (annealed at 300 °C) and 8 nm (annealed at 500 °C) sized nanocrystals of yellow inorganic pigment Bi4Zr3O12 prepared by sol-gel auto-combustion technique. Increase in the annealing temperature from 300 °C to 500 °C does not led to structural phase change but results in minor shifts in the 2θ position of Bragg peaks towards the higher angle side, which is attributed to reduction in the unit cell volume due to well crystallization. Phase pure formation and well crystallization of 8 nm sized Bi4Zr3O12 pigment in the fluorite type fcc symmetry in the space group Fm3‾m (No. 225) have been revealed first time by detailed Rietveld profile refinement of the X-ray diffractogram, FTIR, SAED and HRTEM analysis. The FESEM micrographs showed micro-flower type morphology of the rod shaped nanocrystals of the Bi4Zr3O12 pigments. EDS and XPS analysis confirmed the stoichiometry of the constituent elements present in the Bi4Zr3O12 pigments. XPS analysis evaluated +3, +4 and −2 oxidation states of the Bi, Zr and oxygen ions respectively and also rule out presence of organic species in the two pigments. ESR, Fluorescence and XPS analysis affirmed formation of oxygen vacancies in the two pigments. UV–Vis–NIR optical reflectance data showed marginal increment in the optical band gap upon raising the annealing temperature but 8 nm sized Bi4Zr3O12 nanocrystals have shown greater reflectance in comparison to 5 nm sized Bi4Zr3O12 nanocrystals. The photoluminescence spectroscopic analysis and CIE coordinates along with CCT values showed that yellow Bi4Zr3O12 pigment could be useful for optical devices and yellow pigment applications.

Fluid Inclusions and REE Geochemistry of White and Purple Fluorite: Implications for Physico-Chemical Conditions of Mineralization; an Example from the Pinavand F Deposit, Central Iran

The Pinavand fluorite deposit is hosted by lower Cretaceous carbonate rocks in the structural-geological transitional zone of Central Iran. The purple and white fluorite occur, respectively, as early replacement masses and late cross-cutting veins. Both fluorites have different and distinct physicochemical characteristics. The purple fluorite has higher homogenization temperatures of fluid inclusions (170–260 °C) and lower ∑REE (1.6 ppm) and Y (1.3 ppm) than the white variety (90–150 °C, 11.12 ppm, and 21.3 ppm, respectively). All fluorite samples show positive Y anomalies (Y/Y*) in the range of 1.15–3.5. The average values of La/Ho in the purple and white fluorites are 23.1 and 3.4, respectively. The purple fluorite samples have lower Y/Ho values (an average of 63.45) than the white fluorite samples (an average of 87.64). The Tb/Ca ratio in the Pinavand fluorites ranges between 0.0000000348 and 0.00000105, and the Tb/La ratio varies between 0.01 and 0.4; these values suggest that both fluorite types are “hydrothermal” in origin. The purple fluorites have a lower Sr and a negative Eu anomaly. These differences in concentrations and ratios of various REE suggest that the physico–chemical conditions of mineralization changed during fluorite deposition at the Pinavand. These changes correspond to an increase in oxygen fugacity and pH, which occurred during white fluorite mineralization at lower temperatures. The δ34S values of the Pinavand barite samples (an average of 23.25‰) are similar to those of seawater sulfate in the upper Proterozoic. The δ34S values of galena range from −0.2‰ to −3.7‰, compatible with bacterial sulfate reduction (BSR). These features are similar to those in the hydrothermal and magmatic deposits.

Study of photodegradation performance of Zn‐doped CeO2 nanoparticles for wastewater contaminants remediation under visible light

The presented paper introduces a green route for the arrangement of pure and 1%, 2%, and 4% zinc doped cerium oxide nanoparticles (Zn‐doped CeO2 NPs) by involving the extract of Salvadora persica. The analytical results of powder X‐ray diffraction (PXRD), ultraviolet–visible (UV–Vis), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray (EDX), and Raman techniques confirmed the successful synthesis of NPs. According to PXRD outcomes, pure CeO2 NPs have a cubic phase. Moreover, as a result of the zinc doping within the crystal framework of this material, a noticeable alteration was observed in the placement of CeO2 (101) peak. The size of pure CeO2 NPs was measured by the FESEM analysis to be around 20–25 nm, which was decreased with the doping of zinc into CeO2 structure. According to the UV–Vis outcomes, appeared peak in 343 cm−1 confirmed the formation of CeO2 NPs; and this peak shifted by the doping of zinc. The observed Raman active band F2g at 459 cm−1 in the graph of CeO2 can be related to the fluorite type of CeO2 construction. Moreover, we evaluated the photocatalytic functionality of the prepared samples towards acid orange 7 (AO7) dye at visible light. The gathered data indicated 2% Zn‐doped CeO2 as the optimum sample due to eliminating 83% of AO7 dye at the volume of 15 mg L−1 in pH = 7. Therefore, performing a doping process on these NPs was a suitable choice for improving the photocatalytic activity of CeO2 on AO7 dye.

Phase relation studies in the CeO2-La2O3-Ho2O3 system at temperature of 1500 °С

The phase equilibria in the ternary CeO2–La2O3–Ho2O3 and binary La2O3–Ho2O3 and CeO2–Ho2O3 systems at a temperature of 1500 °С in the whole concentration range were studied. No new phases have been identified in these systems. An isothermal cross section of the state diagram of the CeO2–LaO2–Ho2O3 system at a temperature of 1500 °С is constructed. It was found that the following solid solutions are formed in the studied systems: cubic solid solutions with a structure of fluorite type F-CeO2, as well as solid solutions based on monoclinic (B), hexagonal (A) and cubic (C) modifications of Ln2O3. It was found that cubic solid solutions of the fluorite type F-CeO2 are in equilibrium with all phases formed in the ternary system CeO2– La2O3–Ho2O3 at a temperature of 1500 °С. The boundaries of phase fields and lattice parameters of the formed phases for all investigated systems are determined. A brief description of the structure of isothermal cross sections of ternary state diagrams of systems of the CeO2–La2O3–Ln2O3 series at a temperature of 1500 °С is given. It is established that the systems of this series have a similar structure, although they are characterized by some differences due to the polymorphism of the original components.

The Electrical Properties of Zr Doped Ce0.6Y0.4O2- δ Solid Electrolytes for Solid Oxide Fuel Cell Applications

Ionic conducting solid electrolytes based on doped ceria has been studied widely. In this work, we are studying the effect of Zr4+ substitution on the solid electrolyte system Ce0.6-xZrxY0.4O2-δ where x = 0, 0.2, 0.4, and 0.6. The samples were synthesized by mechanical milling and the evolution of their structure with milling time was analyzed by X-ray diffraction (XRD). The milled powders were uniaxially pressed and sintered at different temperatures (1200 and 1500 °C) and the morphology was analyzed by scanning electron microscopy (SEM) and the electrical properties were measured using impedance spectroscopy. XRD analysis shows the formation of fluorite type cubic phases after 20 h of milling and with increasing the sintering temperature from 900 to 1200 °C shows the transformation of cubic fluorite phase to a tetragonal phase. The analysis of electrical properties shows a decrease in conductivity with the substitution of Zr4+ in Ce0.6-xZrxY0.4O2-δ oxide.

Greener route for synthesis of cerium oxide and Fe-doped cerium oxide nanoparticles using acacia concinna fruit extract

Abstract Nanomaterials have enabled extraordinary technical breakthroughs relative to bulk materials because of their unique properties. In this study, we have synthesized CeO2 and Ce1−x Fe x O2 (x = 0.02, 0.04 and 0.06 w/w) nanoparticles by the sol–gel method using acacia concinna fruit extract. The crystallite size of 22.7 nm for CeO2 and varied from 32.47 nm to 62.95 nm for Fe-doped CeO2 nanoparticles as calculated from the X-ray diffraction pattern. Scanning electron microscope images showed a porous network-like morphology for both the samples. Fourier transform infrared spectroscopy showed a characteristic absorption band for Ce–O at 849 cm−1. Raman spectra indicated the vibrational mode of the cubic fluorite type structure of CeO2 nanoparticles at 464 cm−1. The specific surface area of CeO2 nanoparticles, was observed to be 58 m2 g−1, while that for 2%, 4%, and 6% Fe-doped CeO2 nanoparticles was 45 m2 g−1, 34 m2 g−1, 24 m2 g−1 respectively.

Efficient adsorption and antimicrobial application of bio-synthesized porous CeO2 nanoparticles

The present research demonstrates the green synthesis of CeO2 nanoparticles (NPs) using the Acacia Concinna fruit extract by sol–gel route. The synthesized CeO2 NPs are applied for the adsorptive removal of Reactive Blue (RB) azo dye and antimicrobial activities. The CeO2 NPs are characterized using different techniques e.g. X-ray Diffraction Spectroscopy (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), UV–vis Spectroscopy, Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Dynamic Light Scattering (DLS), Raman Spectroscopy, etc. The structural investigations (XRD) reveal the single-phase cubic fluorite-type structure of CeO2 with 22.7 nm of crystallite size. The spectral analysis (FTIR) shows a strong vibration band below 849 cm−1 owing to Ce-O-Ce stretching vibrations. A porous network-like morphology of the CeO2 NPs is observed by SEM, where HR-TEM micrographs reveal that the nanoparticles are roughly spherical in nature. Raman spectroscopy confirms the vibrational mode of the cubic fluorite type structure of CeO2 NPs at 462 cm−1. The maximum loading capacity of CeO2 NPS is 188.67 mg/g. The antibacterial activity of the CeO2 NPs is evaluated against S. pneumoniae and E.coli, which shows 96.17 % and 96.89 % growth inhibition at 20 mg/l.

Phase equilibria in the ZrO2–HfO2–Sm2O3 system at 1500 °С

The phase equilibria in the ternary system ZrO 2 –HfO 2 –Sm 2 O 3 were studied by X-ray diffraction and microstructural analyses. The formation of new phases in the ZrО 2 –HfO 2 –Sm 2 O 3 system at 1500 °С was not observed. It is established that in the studied system at 1500°C the fields of solid solutions based on tetragonal (T) modification of ZrО 2 , monoclinic (M) modifications of HfO 2 , and monoclinic (B) modifications of Sm 2 O 3 , and ordered phase with the structure of pyrochlore-type (Py) Ln 2 Zr 2 O 7 (Ln 2 Hf 2 O 7 ) are present. The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. The studied isothermal cross section of the ZrО 2 –HfO 2 –Sm 2 O 3 system is characterized by the formation of continuous series of cubic solid solutions based on a phase with a structure of the pyrochlore-type Sm 2 Zr 2 O 7 (Sm 2 Hf 2 O 7 ) and a structure of the fluorite type F-ZrO 2 (HfO 2 ). It is established that two regions of homogeneity of cubic solid solutions are formed in the determined system. The existence of these regions of homogeneity is due to the rupture of the solubility of the F-ZrO 2 (HfO 2 ) phase in the region of the existence of an ordered phase with a pyrochlore-type structure Sm 2 Zr 2 O 7 (Sm 2 Hf 2 O 7 ). It is established that the solid solution based on a cubic modification with fluorite-type structure exists in equilibrium with all phases observed in the system. Isothermal section of the phase diagram of the system ZrO 2 –HfO 2 –Sm 2 O 3 at 1500°C has been characterized by the presence of one three-phase (F + T + M), as well as five two-phase (B + F, two - F + Py, M + F, T + F) regions.