Formation Of Impurity Phases Research Articles

Influence of calcium-doped on the conductivity of NASICON-type Na3Zr2Si2PO4 solid electrolyte

Sodium-ion solid electrolyte has many advantages such as high safety, good ionic conductivity, and strong chemical stability. NASICON-type Na3Zr2Si2PO4 solid electrolyte was prepared by high-temperature Solid State Reaction (SSR). X-ray Diffraction (XRD) show that the 20% excess addition of Na and P elements will reduce the formation of ZrO2 impurity phase and increase the ionic conductivity to 1.01×10−4 S cm−1. On the basis of this experiment, Ca was added to dope the Na site in Na3Zr2Si2PO4 with different contents. Electrochemical impedance spectroscopy (EIS) results show that the conductivity of Ca2+ doped Na2.7Ca0.15Zr2Si2PO4 is significantly increased to 1.53×10−4 S cm−1, the electronic conductivity is 3.99×10−8 S cm−1, and the activation energy is 0.32 eV. Cyclic voltammetry testing demonstrated stable chemical properties below to 5 V. Na | Na2.7Ca0.15Zr2Si2PO4 | Na3V2(PO4)3 battery still maintains a high capacity retention rate of 98.76% after 200 cycles at 25oC-0.2C. It indicating that the new 0.15molCa-doped Na2.7Ca0.15Zr2Si2PO4 has the highest electrical conductivity, which provides a new research idea for sodium-ion solid-state batteries and has great potential in solid-state battery applications.

Unveiling the role of Cs ion in perovskite phase formation during solid–vapor reactions

The preparation of perovskite solar cells (PSCs) using a solid–vapor reaction has shown great potential due to its scalability and lack of organic solvent. The phase formation process in the solid–vapor reaction is crucial for the crystallization of perovskite films. Previous studies mainly introduced Cs into the solid–vapor reaction, but insufficient attention was paid to the role of Cs in purifying the phase formation path during the crystallization process. In this study, we investigated the effect of Cs on the phase formation process in the solid–vapor reaction and found that Cs can decrease the crystallinity of lead halide films, induce a purified phase formation process to prevent the formation of δ-phase and other impurity phases, regulate the crystallization rate of perovskite, and produce high-quality, low-defect perovskite films. The result was achieving a champion power conversion efficiency (PCE) of 21.54 % for a small area (0.148 cm2) and 18.65 % for larger mini-modules (5 × 5 cm2). Furthermore, the devices maintained over 80 % of their initial efficiencies after 450 h of continuous operation under AM 1.5 G irradiation. This work underscores the importance of purified phase formation paths in solid–vapor reactions for outstanding crystal quality in high-performance perovskite solar cells.

Preparation and application of high-performance sodium-ion batteries cathode material Na3.6Fe2.6(PO4)1.6P2O7 with optimized sodium-iron ratio

Na4Fe3(PO4)2P2O7 (NFPP) has been developed as the most promising polyanion cathode for sodium-ion batteries due to its excellent electrochemical performance, high safety properties, and environmental friendliness. However, the electrochemically inactive impurity (m-NaFePO4) will inevitably generate during synthesis process, which decreases the practical capacity of NFPP significantly. In this paper, a novel Na3.6Fe2.6(PO4)1.6P2O7 cathode material with excellent performance is successfully exploited by optimizing sodium-iron ratio to reduce the formation of impurity phases. In a series of as-prepared materials with sodium-iron ratio between 1.33–1.50, Na3.6Fe2.6(PO4)1.6P2O7 exhibits the highest discharge specific capacity (110.3 mAh g−1 at 0.1C), best rate capability (84.4 mAh g−1 at 30 C) and cycle performance (78.2 % capacity retention after 3000 cycles at 20 C). Furthermore, 20 Kg of the Na3.6Fe2.6(PO4)1.6P2O7 cathode material is prepared by spray drying method, which has been successfully applied in sodium-ion pouch cells (12 Ah) with a commercial hard carbon as the anode materials. The assembled pouch cells display excellent cycle performance (82.4 % capacity retention after 2000 cycles at 1 C), rate capability (88 % capacity retention at 30 C) and low-temperature performance (74 % capacity retention at −40 °C).

STUDY OF THE EFFECT OF THE FORMATION OF TWO-PHASE CERAMICS BASED ON NEODYMIUM ZIRCONATE DUE TO DOPING WITH MGO AND Y2O5 ON THE STABILITY OF STRENGTH AND THERMOPHYSICAL PARAMETERS UNDER IRRADIATION

The work presents the study results of the determination of the resistance of neodymium zirconate doped with MgO and Y2O5 to radiation damage stemming from irradiation with heavy ions akin to nuclear fuel fission fragments. The attraction towards this type of ceramics stems from its potential to raise the operational temperatures within the core of next-generation nuclear reactors. This is owed to its superior thermal conductivity when compared to zirconium dioxide, coupled with the heightened strength parameters that signify the ceramics' resistance against external factors. The main results of this study are to determine the influence of the formation of substitution or interstitial phases when adding magnesium and yttrium oxides to the composition, on increasing the stability of the strength and thermophysical parameters of neodymium zirconate to the radiation defects accumulation in the damaged surface layer. During the studies, it was found that the formation of impurity phases in the form of MgO inclusions (when it is added to the composition) and a substitution phase of the Y2Zr2O7 type (with the addition of Y2O5) results in an elevation in the hardness and crack resistance stability of neodymium zirconate ceramics, which indicates the positive effect of doping linked to the formation of additional interphase boundaries that prevent strain embrittlement of the damaged layer under high-dose irradiation. During determination of the thermophysical parameters of the studied neodymium zirconate ceramics, it was observed that the formation of interphase boundaries during doping not only enhances thermal conductivity but also mitigates the decline in the thermal conductivity coefficient during irradiation for two-phase ceramics in comparison with undoped neodymium zirconate ceramics.

Li-Site Defects Induce Formation of Li-Rich Impurity Phases: Implications for Charge Distribution and Performance of LiNi0.5- xMxMn1.5O4 Cathodes (M = Fe and Mg; x = 0.05-0.2).

An understanding of the structural properties that allow for optimal cathode performance, and their origin, is necessary for devising advanced cathode design strategies and accelerating the commercialization of next-generation cathodes. High-voltage, Fe- and Mg-substituted LiNi0.5Mn1.5O4 cathodes offer a low-cost, cobalt-free, yet energy-dense alternative to commercial cathodes. In this work, the effect of substitution on several important structure properties is explored, including Ni/Mn ordering, charge distribution, and extrinsic defects. In the cation-disordered samples studied, a correlation is observed between increased Fe/Mg substitution, Li-site defects, and Li-rich impurity phase formation-the concentrations of which are greater for Mg-substituted samples. This is attributed to the lower formation energy of MgLi defects when compared to FeLi defects. Li-site defect-induced impurity phases consequently alter the charge distribution of the system, resulting in increased [Mn3+] with Fe/Mg substitution. In addition to impurity phases, other charge compensators are also investigated to explain the origin of Mn3+ (extrinsic defects, [Ni3+], oxygen vacancies and intrinsic off-stoichiometry), although their effects are found to be negligible.

Optimizing the curie temperature of La0.67Sr0.33MnO3–based composite materials around room temperature through the addition of Mo, Mn, and Ni metallic elements

Our study sheds light on the role of secondary phases in optimizing the magnetic properties of LSMO, offering valuable insights into the relationship between impurity phases, Curie temperature (TC), and magnetic entropy change. To achieve this goal, the Mn, Ni, and Mo elements were individually incorporated into the LSMO matrix to the formation of secondary phases. The solid-state reaction method was employed to create composite materials of (0.8)La0.67Sr0.33MnO3 + (0.2)A (A=Mn, Ni, and Mo). XRD and SEM results confirmed the successful formation of impurity phases within the main LSMO phase. From temperature-dependent magnetization (M(T)) measurements, it was determined that the TC of the samples approach towards room temperature with the existence of impurity phases. Additionally, the relationship between electron bandwidth (W) and TC was examined. The lowest TC value was observed for the lowest value of W. Besides these, the effect of the formation of impurity phases on the maximum magnetic entropy change (-ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{M}^{max}$$\\end{document}) value is examined, and it is seen that impurity phases cause a decrease in the (-ΔSMmax)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(-\\Delta {S}_{M}^{max})$$\\end{document} values.

Structure and ionic conductivity of NASICON-type LATP solid electrolyte synthesized by the solid-state method

The area of commercial battery innovation to replace safer batteries in widely used secondary batteries offers promising research into solid-state electrolytes (SSEs). Compared to lithium-ion electrolytes, solid-state electrolytes are inherently safer because they replace solvents with non-flammable materials. One of the promising materials for electrolytes today is based on inorganic materials, especially ceramics. Ceramics with superior mechanical, chemical and electrochemical stability and stability against high temperatures are of great interest. NASICON structured Li1.3 Al0.3 Ti1.7 (PO4)3 (LATP) is the most studied type of solid electrolyte due to its stability against air and humidity and high ionic conductivity.In this study, LATP samples were synthesized by solid-state synthesis method. The structural, morphological and charge transport properties (ionic conductivities) of the synthesized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Since the modifications applied during the sample preparation process can change the crystal structure and size of the target material, in this study, in order to minimize the formation of impurity phases and to achieve high ionic conductivity it was applied the different synthesis steps (temperature, time, grinding speed, etc.) from the literature. While the ionic conductivity value obtained is among the best values obtained by LATP synthesis methods in the literature, it is the best ionic conductivity value (1.3 × 10−3 S cm−1) obtained by the solid state synthesis method.

Porous PbBr2 films modulation by indium tribromide additive for the fabrication of SnO2-based CsPbBr3 perovskite solar cells

The achievement of complete conversion of PbBr2 films presents a significant challenge in the development of CsPbBr3 films with consistent growth, comprehensive coverage, and controllable components. To address this challenge, introducing a porous structure in the planar PbBr2 film is advantageous for facilitating the immersion of CsBr precursor, thereby reducing impurity phase formation and mitigating strain caused by the film volume expansion. In order to accomplish this, indium tribromide (InBr3) was employed as an additive and the InBr3(DMF)3 adduct was utilized to expedite the release of organic molecules in PbBr2(DMF), resulting in the transformation of planar PbBr2 film into porous structures. The growth orientation of PbBr2 crystals was altered by this transformation, effectively suppressing the generation of metallic Pb impurities in the film. Additionally, it not only optimizes the morphology of CsPbBr3 film but also reduces impurity phase. As a result, the InBr3:CsPbBr3 perovskite solar cell achieved an efficiency of 7.28 %. The majority of In3+ ions were concentrated near the buried interface between SnO2 and InBr3:CsPbBr3, leading to significant improvements in both non-radiative recombination defect states within the perovskite film and electron injection and collection capabilities within the device.

Surface plasma treatment boosting antiferroelectricity and energy storage performance of AgNbO3 film

The utilization of AgNbO3 film in dielectric energy storage poses challenges due to its susceptibility to impurity phase formation, which compromises its antiferroelectric properties and breakdown electric field. In this study, we successfully fabricated an AgNbO3 film with outstanding antiferroelectric properties and energy storage capabilities by employing oxygen ion surface plasma technology in conjunction with the sol-gel method. Our results demonstrate that the surface of the AgNbO3 film undergoes a layer-by-layer treatment using oxygen ion plasma, effectively suppressing impurity phases and oxygen vacancies formation while reducing grain size and enhancing insulation performance. The AgNbO3 film, which has undergone surface plasma treatment with oxygen ion, exhibits exceptional characteristics as an antiferroelectric material by demonstrating an impressive energy storage density of 13.13J/cm3 and a high energy storage efficiency of 56%. Overall, we present a straightforward and viable approach for fabricating high-performance AgNbO3 films for efficient dielectric energy storage.

Defect chemistry engineering of Ga-doped garnet electrolyte with high stability for solid-state lithium metal batteries

Abstract Ga-doped Li7La3Zr2O12 (Ga-LLZO) has long been considered as a promising garnet-type electrolyte candidate for all-solid-state lithium metal batteries (ASSLBs) due to its high room temperature ionic conductivity. However, the typical synthesis of Ga-LLZO is usually accompanied by the formation of undesired LiGaO2 impurity phase that causes severe instability of the electrolyte in contact with molten Li metal during half/full cell assembly. In this study, we show that by simply engineering the defect chemistry of Ga-LLZO, namely, the lithium deficiency level, LiGaO2 impurity phase is effectively inhibited in the final synthetic product. Consequently, defect chemistry engineered Ga-LLZO exhibits excellent electrochemical stability against lithium metal, while its high room temperature ionic conductivity (∼ 1.9 × 10−3 S⋅cm−1) is well reserved. The assembled Li/Ga-LLZO/Li symmetric cell has a superior critical current density of 0.9 mA⋅cm−2, and cycles stably for 500 hours at a current density of 0.3 mA⋅cm−2. This research facilitates the potential commercial applications of high performance Ga-LLZO solid electrolytes in ASSLBs.

TUDY OF THE INFLUENCE OF THE ACCUMULATED DOSE OF DAMAGE IN THE NEAR-SURFACE LAYER ON RESISTANCE TO EXTERNAL INFLUENCES ASSOCIATED WITH CORROSION PROCESSES DURING HIGH-TEMPERATURE ANNEALING

Abstract. Investigating the challenges associated with the structural and strength degradation of ceramic fuel cells, which hold significant potential for hydrogen production through electrolysis methods, is a current focus ofresearch. Understanding the degradation processes and their occurrence rate is crucial in the assessment of the efficacy of these ceramics for applications in alternative energy production, specifically in the realm of hydrogen energy. The aim of this study is to ascertain the impact of doping ceramics with aluminum nitride NiAl2O4, irradiated with protons with a dose of approximately 50 dpa, on resistance to high-temperature degradation, and associated corrosive processes of oxidation and swelling, as well as migration processes of implanted hydrogen. Three types of ceramics were selected as objects for study: NiAl2O4ceramics, NiAl2O4ceramics stabilized with 0.05 M AlN, NiAl2O4ceramics stabilized with 0.15 M AlN, that are distinguished by the formation of impurity phases in Al7O3N8, with an orthorhombic type of crystal lattice. As a result of high-temperature tests, it was observed that NiAl2O4ceramics, when stabilized, exhibit reduced susceptibility to destructive alterations in strength characteristics, primarily attributed to the deformation distortion of the crystal structure caused by its swelling. These processes are associated with an augmentation in the thermal expansion of the crystal structure, manifested in the deformation swelling of the crystal lattice volume.

Charting the Irreversible Degradation Modes of Low Bandgap Pb‐Sn Perovskite Compositions for De‐Risking Practical Industrial Development

AbstractThe commercialization of a solar technology necessitates the fulfillment of specific requirements both regarding efficiency and stability to enter and gain space in the photovoltaic market. These aims are heavily dependent on the selection of suitable materials, which is critical for suppressing any reliability risks arising from inherent instabilities. Focusing on the absorber material, herein the most suitable low bandgap lead‐tin composition candidate for all‐perovskite tandem applications is investigated by studying their degradation mechanisms with both widely available and advanced characterization techniques. Three irreversible degradation processes are identified in narrow bandgap Pb‐Sn perovskite absorbers: 1) Tin (Sn) oxidation upon air exposure, 2) methylammonium (MA) loss upon heat exposure, and 3) formamidinium (FA) and cesium (Cs) segregation leading to impurity phase formation. From an industrial perspective, it is proposed to refocus attention on FASn0.5Pb0.5I3 which minimizes all three effects while maintaining a suitable bandgap for a bottom cell and good performance. Moreover, a practical and highly sensitive characterization method is proposed to monitor the oxidation, which can be deployed both in laboratory and industrial environments and provide useful information for the technological development process, including, the effectiveness of encapsulation methods, and the acceptable time windows for air exposure.

Composite solid electrolytes based on Li7La3Zr2O12 for all-solid-state lithium power sources

Currently development of all-solid-state lithium batteries are in great demand all over the world. Li7La3Zr2O12 (LLZ) compounds are considered as perspective solid electrolyte for such power sources. However, these solid electrolytes of garnet family have some disadvantages – high temperatures of ceramic synthesis, poor wettability by Li and low stability to air components. The creation of composite solid electrolytes based on LLZ is one of the ways to solve these problems. It was established that the temperature and/or sintering time of the solid electrolyte could be reduced by the introduction of different additives with maintaining lithium-ion conductivity values (10–5–10–4 S/cm at room temperature). It should be noted that the used sintering additive should meet the following requirements: low softening temperatures, high values of lithium-ion conductivity, stability in contact with lithium metal and absence of chemical interaction between components leading to the formation of low-conductivity impurity phases. Thus, the development of composite solid electrolytes based on LLZ is perspective for all-solid-state power sources.

Enhanced thermoelectric properties of In-filled Co4Sb12 by dispersion of reduced graphene oxide.

Uniform dispersion of nanosized secondary phases in bulk thermoelectric materials has proven to be an effective strategy to reduce the lattice part of thermal conductivity and improve the thermoelectric efficiency. In this work, reduced graphene oxide (rGO) was uniformly dispersed in the In0.5Co4Sb12 bulk material by ultrasonication. The formation of impurity phases of InSb and CoSb2 in the In-filled Co4Sb12 is inevitable, as observed from XRD and EPMA analyses. The Raman spectra of the nanocomposites showed broad peaks suggesting phonon softening and additional peaks corresponding to rGO. Electron transport was not affected by rGO addition, resulting in little change in the electrical resistivity and Seebeck coefficient. The lattice thermal conductivity of the bulk material was significantly reduced by the addition of a small amount of rGO, primarily attributed to the interface scattering of phonons. Hence, the highest zT of ∼1.53 at 773 K was achieved for the In0.5Co4Sb12/0.25 vol% rGO composite in the temperature range from 723 K to 773 K.

Chemical stability aspects of BaCe0.7–xFexZr0.2Y0.1O3–δ mixed ionic-electronic conductors as promising electrodes for protonic ceramic fuel cells

Mixed ion-electron conductors (MIECs) are promising materials for air electrodes for protonic ceramic fuel cells (PCFCs) or oxygen permeation membranes. In this work, various aspects of the chemical stability of Co-free MIEC materials, BaCe0.7–xFexZr0.2Y0.1O3–δ, were studied, including their interaction with another functional material (BaCe0.5Zr0.3Y0.1Yb0.1O3–δ-based proton-conducting electrolyte) and gas components (H2O, CO2, and H2). Chemical compatibility studies indicate no visible chemical interaction between the electrode and electrolyte materials even at 1200 °C, which is significantly higher than the operating temperatures (600–800 °C) of PCFCs. The treatments of BaCe0.7–xFexZr0.2Y0.1O3–δ in different atmospheres at 1100 °C, according to the XRD, SEM, IR and Raman spectroscopy data, resulted in the formation of impurity phases. However, their extremely small amounts suggest that they may not form at the operating temperatures. Thus, it can be assumed that the studied materials can be good candidates for various electrochemical applications.

Microstructure evolution and properties of LaB6 modified carbon-free sintered FeCoMo steels

LaB6-modified carbon-free FeCoMo steels with nano-precipitated phase strengthening have shown excellent sintering and mechanical properties, which enhances their application potential. The results showed that LaB6 promoted the precipitation of sub-nanometer μ-phase particles from the matrix and reduced the formation of impurity phases during the sintering process. The addition of 0.2 wt% LaB6 increased the hardness, wear resistance and red hardness of FeCoMo steel by 5.1 %, 26.3 % and 12.6 %, respectively. This study creates conditions for the application of carbon-free FeCoMo steels by introducing LaB6 to improve their sintering properties and precipitated phase strengthening efficiency.

Enhanced thermoelectric performance of NbCoSb half-Heusler alloys by using an amorphous precursor

Amorphous flakes with a stoichiometric composition of NbCoSb were successfully synthesized by introducing a rapid solidification technique. The amorphous phase transformed into a nanostructured NbCoSb half-Heusler phase with a valence electron count (VEC) of 19 during spark plasma sintering. Due to the chemically homogeneous nature of amorphous phase, uniform nanostructure of NbCoSb half-Heusler phase was obtained within the disk samples without impurity phase formation as well as long term annealing treatment required in the conventional manufacturing process. Nanostructuring of NbCoSb half-Heusler phase significantly increased grain boundary area in which electron and phonon scattering occurred and was effective to enhance thermoelectric performance. Furthermore, the carrier concentration was reduced by doping with Sn causing an increased dimensionless figure-of-merit ZT value. A maximum ZT value of ∼0.78, corresponding to a two-fold improvement compared to the ZT value of the as-cast sample, was achieved at 1173 K for the sintered NbCoSb0.95Sn0.05 sample.

STUDY OF THE INFLUENCE OF VARIATIONS IN THE PHASE COMPOSITION ON THE DIELECTRIC PROPERTIES OF FERROELECTRIC CaTiO<sub>3</sub> CERAMICS DOPED WITH Y<sub>2</sub>O<sub>3</sub>

The study of the relationship between the effect of phase composition variation on the dielectric characteristics of ferroelectric ceramics is one of the most important fundamental questions, the answer to which will allow us to determine the potential of using ferroelectrics in microelectronic applications and the creation of alternative energy sources (solid oxide fuel cells). The purpose of this study is to explore the effect of the Y2O3 dopant on the phase formation processes and the properties of the synthesized ferroelectric ceramics of calcium titanate, as well as to establish the connection between the influence of the formation of impurity phases on the change in the dielectric properties of ceramics. According to the data of X-ray phase analysis, it was found that the addition of Y2O3 with a concentration above 0.15 M leads to the formation of an orthorhombic CaY2O4 phase in the ceramic structure, the weight contribution of which increases with the dopant concentration growth. An analysis of the dependence of the specific electrical conductivity (σDC) with varying dopant concentration showed that the maximum value of σDC is achieved at dopant concentrations of 0.05 M, which leads to structural ordering due to the effect of adding yttrium oxide acting as a stabilizer, as well as the formation of impurity donor conductivity in the structure. An analysis of the dependence of the specific electrical conductivity (σDC) from dopant concentration was carried out. It has been established that the maximum value of σDC is achieved at a dopant concentration of 0.05 M. This is explained by structural ordering due to the addition of a stabilizer – yttrium oxide, as well as the formation of impurity donor conductivity in the synthesized sample. At the same time, the established dependences of the change in dielectric characteristics are in good agreement with the change in the phase composition, and an increase in the concentration of charge carriers due to the introduction of a donor impurity in the form of Y3+ leads to the appearance of volume-charge polarization in ceramics.

Correlation of the chemical composition, phase content, structural characteristics and magnetic properties of the Bi-substituted M-type hexaferrites

Bi-substituted M-type hexaferrites, BaFe12-xBixO19 (0.1 ≤ x ≤ 1.2), or Bi-BaM, were produced by the solid-state reactions. The correlation between the phase content, chemical composition, crystal structure features, and peculiarities of the magnetic properties of Bi-BaM was established using XRD (X-ray diffraction), SEM (scanning electron microscopy), and VSM (vibrational sample magnetometry). XRD phase analysis made it possible to establish the limit of substitution of Fe3+ ions by Bi3+ ions. It was shown that at a low substitution level (x ≤ 0.3), no impurity phases were detected, and the samples are characterized by a single-phase state with the space group (SG) P63/mmc. As the degree of substitution (x ≥ 0.6) increases, the formation of impurity phases was observed, which can be explained by the difficulties of ion diffusion in the process of solid-phase synthesis as well as the formation of defects in the magnetoplumbite structure due to the large ionic radius of Bi3+. As impurity phases in the studied compositions (x ≥ 0.6) the following were noted: BiFeO3 (SG: Pnma); BiO2 (SG: Fm-3m); BaBi2O6 (SG: R-3); and Ba0.5Bi1.5O2.16 (SG: Im-3m). The content of the main phase (SG: P63/mmc) decreases from 95.11 to 88.27 vol% with an increase in x from 0.6 to 1.2, respectively. Analysis of SEM images showed the growth of particles up to 10 μm, depending on the concentration of bismuth oxide during hexaferrite synthase. The Bi-BaM magnetic characteristics were examined using VSM in the range of 3 T at 300 K. Due to the magnetic structure's frustration, with increased x a decrease in saturation magnetization (Ms) was found. There were two concentration diapasons with different speeds of Ms decrease. In the first diapason, the main contribution belong to the magnetic structure frustration in the frame of the main phase (P63/mmc) due to the long-range Fe-O-Fe exchange interaction weakening (under Bi substitution). In the second diapason, the main contribution belong to the impurity phase formation and decrease of the main magnetic phase concentration in samples.

Effect of Mo-Doping on the Proton-Conducting BaCe0.9-xMoxY0.1O3-δ Electrolyte at Intermediate Temperature SOFCs

Perovskites have been attracting much attention because of their many potential applications as solid electrolytes in solid oxide fuel cells (SOFC). Among various kinds of perovskite materials, the Y2+ doped BaCe0.9Y0.1O3-δ (BCY) have been investigated extensively. It is noted that the doped BCY have good stability and relatively high protonic conductivity. However, the sintering temperature of BCY is very high above 1600 °C to achieve the required densification. High sintering temperature leads to evaporation of barium and the subsequent segregation of doped elements. As a result of this, the electrochemical properties of BaCe0.7Zr0.1Y0.2O3-δ electrolyte are reduced. At high temperatures, it’s difficult to maintain the porous structure of electrodes and causes the formation of impurity phases. So, in order to overcome this issue, we doped Mo- to BCY and reduce the sintering temperature of the electrolyte without comprising its performance. The sol-gel method was followed for the preparation of Ba1Ce0.9-xMoxY0.1O3-δ (BCMY, x=0.025%-0.2%) powder. The precursor's Ba(NO3)2, Ce(NO3)3.6H2O, Y(NO3)3.6H2O, and (NH4)6Mo7O24.4H2O in the stoichiometric ratio were dissolved in a mixture of water, citric acid, and glycine used as chelating agents in the molar ratio of 1:2:1. The solution was heated at 100 °C and was constantly stirred till it becomes a gel. The dried precursor was then heated at 350 °C for 2 hrs to remove the organic residues through combustion. Afterward, it was calcined at a temperature of 1100 °C for 10 hrs and finally, a white powder of BCMY was obtained. The synthesized BCMY electrolytes were sintered at 900, 1000, and 1100 °C to observe the effects of low sintering temperature on the structural, morphological, and electrical properties of BCMY. All BCMY electrolyte materials exhibited a crystalline perovskite structure and were found to be thermally stable as shown in XRD (Fig. 1 (a, b)). The morphology and element distribution of the BCY and BCMY electrolyte were observed by the scanning electron microscope (SEM, (Fig. 1c)) and energy-dispersive x-ray spectroscopy (EDX). SEM images show that BaCe0.9Y0.1O3-δ electrolyte sinterability and densifications are significantly improved. Fully dense pellets are sintered by using 0.025-0.2 mole% Mo. Energy dispersive spectroscopy shows that sintering aids are uniformly distributed throughout the structure. This study demonstrates BCMY as a dense proton-conducting electrolyte for intermediate-temperature solid oxide fuel cells. The BCMY with Mo-doping appears to be a potential candidate for sintering at low temperatures. Sintering facilitates addition from oxygen vaccines, which ease ionic conduction through the electrolyte, result in a low activation energy of at moderate temperatures. Fully dense pellets are sintered by using 0.025-0.2 mole% Mo. This method of decreasing the BCMY sintering temperature is useful in improving the SOFC performance.