Citrate Nitrate Auto-combustion Method Research Articles

La3+ substitution-adjusted magnetic and optical properties with enhanced photocatalytic activity and stability of copper zinc nickel ferrites for wastewater treatment applications

Copper-zinc-nickel (Cu–Zn–Ni) ferrite nanoparticles are used for wastewater treatment technology. However, low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs. In this paper, the citrate-nitrate auto-combustion method was applied for the formation of Cu0.5Zn0.25Ni0.25LaxFe2–xO4; (0≤x≤0.1; step 0.02) (CZNL) nanoferrites. Although the substitution process entails the replacement of a small ion with a larger one, the lattice constant and crystallite size does not exhibit a consistent incremental pattern. This behavior is justified and discussed. The size of all the CZNL ferrite nanoparticles is in the range of 8–12 nm, and the lattice constant is in the range of 8.6230 to 8.4865 nm. The morphological analysis conducted using field emission-scanning electron microscopy (FE-SEM) reveals that the CZNL exhibits agglomerated spherical morphology. The energy dispersive X-ray spectrameter (EDAX) analysis was employed to confirm the elemental composition of CZNL nanoferrites. Since the process entails the substitution of Fe3+ magnetic ions with non-magnetic ions La3+, the magnetic parameters of CZNL nanoferrites show a general decreasing trend as predicted. At 20 K, saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x = 0.0–41.295 emu/g at x = 0.1, the smallest value of 37.87 emu/g is recorded at x = 0.06. the highest coercivity (Hc = 125.9 Oe) and remanence (Mr = 13.32 emu/g) are recorded for x = 0.08 and x = 0.04 nanoferrite, respectvely. The band gap of all the CZNL nanoferrites was determined using the Kubelka–Munk function and Tauc plot for direct permitted transitions. La doping modifies the band gap (within 1.86–1.75 eV), increases light absorption, induces efficient e/h separation and charge migration to Cu0.5Zn0.25Ni0.25LaxFe2–xO4 surfaces. The nanoferrite Cu0.5Zn0.25Ni0.25La0.06Fe1.94O4 achieves a degradation efficiency of 97.3% for methylene blue (MB) dye removal after just 60 min. After five recycling processes, the nanocatalyst Cu0.5Zn0.25Ni0.25La0.06Fe1.94O4 is degraded by 95.83%, resulting in a negligible 1.51% decrease in photocatalytic activity efficiency. The new Cu0.5Zn0.25Ni0.25La0.06Fe1.94O4 has exceptional photocatalytic activity and remarkable stability, making it a promising candidate for applications in wastewater treatment.

Bi3+ doping-enhanced optical and photocatalytic activity with stability of cobalt nickel zinc ferrites for wastewater treatment applications

In this paper, the spinel ferrite nanoparticles Co0.5Ni0.25Zn0.25BixFe2−xO4 (CNZBF) were prepared by citrate-nitrate auto combustion method. Although the substitution process involves a large ion at the expense of a small one, the lattice constant didn't introduce a regular increment behavior with irregular shifts for the peak position at 34.62°, which is related to the (311) plane. Two hypotheses were introduced to justify this behavior. The crystallite size introduced a peculiar behavior in the span of 20.88–14.78 nm with increasing the Bi3+ content. Morphological study via FE-SEM manifested that the CNZBF nanoferrites have agglomerated spherical shapes. Kubelka-Munk function and Tauc's plot for direct allowed transitions were utilized to determine the band gap of all the CNZBF nanoferrites. The doping of Bi tuned the band gap (within 1.55 to 1.25 eV), boosted the light absorption, induced efficient e/h separation, and ensuing charge migration to the Co0.5Ni0.25Zn0.25BixFe2−xO4 surfaces. On account of the CNZBF advantages, a superb removal efficiency (∼96.41 %) of the sample Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 via photocatalytic degradation was achieved. After five reusability cycles the nanocatalyst Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 introduced 95.08% degradation which demonstrates a trivial efficiency decline of 1.33 % in the photocatalytic activities. These outcomes of excellent photocatalytic activity with the outstanding stability candidate the novel Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 for wastewater treatment applications.

Impact of cobalt doping on magnetic and structural properties in Ce1−xCoxO2 (x = 0.1, 0.2 and 0.3) ceramics synthesized by combustion method

In this investigation, cobalt doped ceria nanopowders, Ce1-xCoxO2 (x = 0.1, 0.2 and 0.3mol.%) were synthesized by citrate–nitrate auto-combustion method at 500 °C in an open furnace. The prominent X-ray diffraction pattern peaks corresponding to the crystallographic planes (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0) and the cell parameters confirm the cubic fluorite crystal structure of the ceria with the help of powder diffraction standard (JCPDS card No.00-034-0394). The UV–Visible absorption due to the charge transfer of O2− → Ce2+ and other functional groups were studied by UV–Visible and FT-IR spectroscopic analyses. The visible light emission (wavelength of 420 nm and 520 nm are corresponding to the defect levels of the O 2p and Ce 4f bands) due to oxygen and other vacancies were confirmed by photoluminescence spectroscopy. Energy band gap (Eg) of the Ce0.9Co0.1O2, Ce0.8Co0.2O2 and Ce0.7Co0.3O2 was found to be 1.423 eV, 1.375 eV and 1.332 eV, respectively. The porosity, agglomeration, particles size, shape and distribution of the synthesized nanoparticles were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). The energy dispersive X-ray spectroscopy (EDX) confirms the presence of constituent elements of Ce1-xCoxO2 such as Ce, Co, and O. The existence of weak ferromagnetism and its variation due to cobalt concentration were studied by vibrating sample magnetometry (VSM) at room temperature.

Development, characterization, and properties of LnSmZr2O7 (Ln = Dy, Ho, Yb) defect fluorite functional ceramics

LnSmZr2O7 (Ln = Dy, Ho, Yb) functional nanoceramics are prepared through a citrate-nitrate auto-combustion method. High-density pellets using the powder are obtained by sintering at 1530 °C for 2 h. The defect fluorite structure of the powder and sintered samples is established using XRD and Raman analysis. The morphology of the powder analyzed using Transmission Electron Microscopy revealed the nanocrystalline nature of the combustion powder. The microstructure of the sintered sample analyzed using Field emission Scanning Electron Microscopy showed increased grain growth with larger cationic substitution. LnSmZr2O7 (Ln = Dy, Ho, Yb) have an indirect-allowed optical wide band gap and exhibit photoluminescence due to intrinsic defect structure. LnSmZr2O7 (Ln = Dy, Ho, Yb) are pure oxide ion conductors in the temperature range from 400 °C to 900 °C, with conductivity values of 0.89 × 10−3 S/cm, 0.72 × 10−3 S/cm and 0.60 × 10−3 S/cm, respectively, at 900 °C.

Tuning the microstructure, magnetostatic and magnetodynamic properties of highly Al-substituted M-type Sr/Ca hexaferrites prepared by citrate-nitrate auto-combustion method

Double substitution of strontium hexaferrite by calcium and aluminum leads to a tremendous rise of hard magnetic properties, such as coercivity and natural ferromagnetic resonance frequency (NFMR). However, the properties are also inextricably linked to the material microstructure (especially, particle size), to the solid solution inhomogeneity as well as aluminum ions distribution among iron sites in crystal structure. In this work, we obtained M-type hexaferrite particles Sr1-x/12Cax/12Fe12-xAlxO19 (x = 4–6) via a facile citrate-nitrate auto-combustion method and studied the influence of the annealing temperature in a broad range on the microstructure, features of crystal structure and hard magnetic properties. At low annealing temperatures (900–1000°С) hexaferrite nanoparticles with 90% of nominal Al content and a wide chemical distribution are formed. Next, with an increase in the annealing temperature the distribution significantly narrows, chemical composition becomes close to the nominal one and particles size transfer firstly to submicron, then to micron range. The aluminum distribution over iron sites is independent distinctly on the annealing temperature. For all the compositions single domain particles with the maximum coercivity values between 22.8 and 36 kOe are obtained at 1200 °C. At 900–1000 °C the samples demonstrate coercivities up to 25 kOe, while above 1300 °C, the crystallites begin to pass into a polydomain state with a reduced coercivity. The hexaferrites with narrow chemical distribution reveal resonance absorption in sub-terahertz band. The highest NFMR frequency of 270 GHz was observed for x = 5.5 sample annealed at 1400 °C.

Synthesis and Characterization of CaFe1.925Gd0.025Sm0.05O4/PEG Core–Shell Nanoparticles for Diverse Applications

The core–shell structure has been studied by coating polyethylene glycol (PEG) on rare-earth-doped calcium ferrite nanoparticles (RCFNPs). RCFNPs are successfully synthesized in the formula CaFe1.925Gd0.025Sm0.05O4 by the citrate nitrate auto-combustion method. The XRD pattern of PEG-coated RCFNPs observed two peaks at 19.3° and 23.6° confirming the existence of PEG, while the other peaks are attributed to the orthorhombic structure formation. The obtained samples exhibit an orthorhombic single-phase structure with an average crystallite size in the range of 18–20 nm. The elemental analysis is performed using EDAX and XPS. The doublet spectrum of Fe atoms corresponds to the valence states Fe 2P1/2 and Fe 2P3/2. High-resolution transmission electron microscopy (HRTEM) revealed a well-designed hexagonal core/shell structure represented as a unique hexagonal PEG shell coating the synthesized RCFNPs. The magnetic hysteresis loops have been recorded using VSM. The coupling between the unpaired electrons of Fe+3 and Sm+3 ions via the p orbitals of the O−2 ions leads to the antiferromagnetic alignment. The smaller values of the switching-field distribution (SFD) and higher coercivity of the prepared samples are most appropriate for ultra-high-density recording performance. The behavior of dielectric parameters is explained on the basis of the interfacial polarization and the Maxwell–Wagner polarization models. Diffuse reflectance spectroscopy (DRS) is used to study the performance of electromagnetic reflection and estimate the optical band gaps of the samples. The obtained data shows that the coating has an important role in enhancing the reflection by up to 50%.

Efficient removal of Pb (II) from water solution using CaFe2−x−yGdxSmyO4 ferrite nanoparticles

Rare-earth doped calcium nano ferrites (CaFe2−x−yGdxSmyO4; x = y = 0.0; x = 0.025, y = 0.05) are synthesized by citrate nitrate auto combustion method. The prepared samples are characterized using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), high-resolution transmission electron microscope (HRTEM), and vibrating sample magnetometer (VSM) analyses. After that, the samples were examined for Pb (II) ions removal from the water solution. The orthorhombic structure with space group Pnma is ratified from XRD. The average crystallite size of the synthesized powders is estimated from the broadening of the XRD lines in the range of 18–21 nm. FTIR confirms the molecular signature of the samples. The magnetic property is discussed based on super exchange interactions. The hysteresis loop shows two different magnetic behaviors of the investigated sample as well as increasing the coercivity from 14 to 240 G due to the doping. The electrical parameters are discussed in the basic hopping charge model, while the conduction mechanism of the samples will be discussed based on de-Boer and Verwey. The experimental results are subjected to kinetic and isotherm analyses. The Langmuir and Freundlich isotherms describe the adsorption of heavy metal ions as designated by the high correlation coefficient (R2). The use only 4 mg of the doped sample with low price ferrite nanoparticles has been utilized for 99.31% removal of Pb (II) from wastewater at a contact time of 10 min at room temperature.

The effect of synthesis method on oxygen nonstoichiometry and electrical conductivity of Sr-doped lanthanum manganites

The strontium-doped lanthanum manganites (La1-xSrxMnO3, LSMO) have potential use in devices for energy conversion and storage due to their chemical stability and high electrical conductivity. In this study, LSMO (x = 0, 0.1, 0.2, 0.3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The formation of the LSMO phase was confirmed by X-ray diffraction and the lattice parameters were determined by Rietveld refinement analysis. The oxygen nonstoichiometry in samples was determined by permanganate titration. The results of electrical conductivity measurement have shown semiconductor behaviuor in all samples, with conductivity rising with temperature and Sr-amount. Furthermore, it was observed that LSMO samples prepared by the coprecipitation method possess higher conductivity than samples prepared with the CNA method due to the higher oxygen nonstoichiometry. Electrical conductivities of all LSMO samples were in 10−2–0.45 Ω−1 cm−1 range, which is comparable to the conductivity of Si.

Simultaneous oxidation of aromatic compounds using Sr‐doped lanthanum manganites as catalysts

Strontium-doped lanthanum manganites, La1-xSrxMnO3 (LSMO), are promising and affordable catalysts for oxidative degradation of volatile organic compounds. LSMO catalysts (x = 0, .1, .2, and .3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The phase composition was confirmed by X-ray diffraction and Rietveld refinement analysis, while the oxygen content was determined by Mohr's salt permanganate titration. Morphology and porosity of prepared catalysts was correlated to catalytic oxidation of benzene, toluene, ethylbenzene and o-xylene. It was observed that both synthesis methods yielded catalysts of similar average pore size diameter and specific surface area, but the pore size distribution differed: CNA-prepared catalysts had a multimodal pore size distribution, while the coprecipitated ones had a single maximum at 4 nm. Catalysts prepared by the CNA method have shown a higher catalytic activity in the temperature range 373–723 K, as the presence of Mn3+/Mn4+ mixed valences increased their reducibility.

Tuning the Microstructure, Magnetostatic and Magnetodynamic Properties of Highly Al-Substituted M-Type Sr/Ca Hexaferrites Prepared by Citrate-Nitrate Auto-Combustion Method

Tuning the Microstructure, Magnetostatic and Magnetodynamic Properties of Highly Al-Substituted M-Type Sr/Ca Hexaferrites Prepared by Citrate-Nitrate Auto-Combustion Method

Structural and Magnetic Tuning of LaFeO3 Orthoferrite Substituted Different Rare Earth Elements to Optimize Their Technological Applications

Lanthanum partially substituted rare earth (RE) elements to form RE0.7La0.3FeO3; RE = Ce, Pr, Nd, Sm and Gd) nanoparticles. They were synthesized using the citrate–nitrate auto-combustion method. The crystal structure and microstructure were refined by applying Rietveld profile refinements using the Maud Program. The morphology, magnetic and optical properties of the inspected samples have been explored using HRTEM, VSM, and UV–Vis diffuse reflectance, respectively. The prepared-samples distortion increases as the substituted RE ionic radius decreases. Iron spins of RE orthoferrite samples are known to be ordered Anti-ferromagnetically (AFM). They also possess weak ferromagnetism due to the Dzyaloshinskii-Moriya interaction. This feeble ferromagnetism is reflected in their soft behavior, whereas Sm0.7La0.3FeO3 sample exhibits the butterfly shape hysteresis loop. The remnant magnetization, saturation magnetization, and coercivity are relatively small, but sometimes impressively, enhanced through Lanthanum-rare-earth substitution. Introducing rare earth ions into LaFeO3 decreases the Fe–O–Fe angle and the consequent reduction of the super exchange interaction. In particular, the coercivity of Sm0.7La0.3FeO3 is remarkably improved relative to the parent sample. It has the largest coercivity of all the prepared nanoparticles. Due to the aforementioned substitution, a slight reflectance edge red shift is observed in the spectra. The relation between the magnetic properties of the investigated samples and the ionic radii of RE was investigated and discussed. The experimental results of this work can provide fundamental support for the research and development of multiferroic materials.

Permanganometric determination of oxygen nonstoichiometry in manganites

Strontium and lanthanum manganites are nowadays the subject of extensive research because of their promising electrical and magnetic properties. Strontium manganite, SrMnO3, was successfully prepared by citrate-nitrate autocombustion (CNA) and by the coprecipitation method. These methods were then applied to synthesis of strontium doped lanthanum manganites, La1-xSrxMnO3 (x ​= ​0, 0.1, 0.2 and 0.3). The optimal phase formation conditions were determined by thermogravimetry and differential scanning calorimetry. Crystallization of precursors and calcined powders was studied by X-ray diffraction. Powders, in which pure manganite phase was obtained, were also analyzed by permanganate titration with Mohr’s salt in order to determine oxygen nonstoichiometry. Oxygen stoichiometry was achieved in SrMnO3 powders obtained by the CNA method and calcined at 1000 ​°C as well as in powders obtained by the coprecipitation method and calcined at 1200 ​°C. La1-xSrxMnO3 phase was oxygen stoichiometric for x ​= ​0.3 while decreasing of x resulted in cation deficiency, i.e. oxygen excess. Oxygen deficit was achieved for x ​= ​0.09 upon calcination at 1200 ​°C. The obtained results were confirmed by thermogravimetry and the Rietveld refinement analysis.

Physical properties of Al-doped cobalt nanoferrite prepared by citrate–nitrate auto combustion method

Cobalt aluminum ferrites have been synthesized by citrate–nitrate auto combustion method. To obtain different crystallite sizes, the prepared powder was heated at different temperatures. X-ray diffraction (XRD) measurements showed that all the prepared samples were crystalized in single phase cubic spinel structure. Different heat treatments lead to different particle sizes which was confirmed by transmission electron microscopy (TEM) micrograph. The crystallite size (D) of the prepared samples ranges from 5 to 37 nm. The structure and elastic properties were investigated using Fourier-transform infrared (FTIR) spectroscopy. The elastic moduli and Debye temperature were calculated out of the FTIR results. The magnetic properties were studied using vibrating sample magnetometer (VSM) and the magnetic parameters; saturation magnetization ( $$M_{\text {S}}$$ ) and coercitvity ( $$H_{\text {c}}$$ ) were determined. The $$M_{\text {S}}$$ and $$H_{\text {c}}$$ size dependence of CoFeAlO $$_{4}$$ nanoparticles introduce a distinctive behaviour; from a structure with multi magnetic domains ( $$D> 9$$ nm) to that without magnetic domains (single domain structure) below $$D= 9$$ nm. Interestingly, the signature of the change from multi-domain to a single magnetic domain is reflected in the size dependence of the elastic moduli and Debye temperature obtained from FTIR results.

Optical And Electrical Properties of PVA/A-Al2O3 Nanocomposite Films

In the present study, a-Al2O3 nanoparticles were synthesized using the citrate-nitrate auto combustion method. Nanocomposites of PVA/a-Al2O3 were intended by solution casting technique. The micrograph of samples were analysed by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and UV-visible spectroscopy analysis. UV-visible results showed that the direct optical band gap decreased with the increase of a-Al2O3 content. The refractive index has been dissected using Wemple and DiDomenico model. Hopping of charge carriers besides interfacial polarization could expound the demeanor of dielectric constant (E'), dielectric loss (E'') and ac electrical conductivity (0-ac) with the frequency and temperatures.

Investigation of Transport Properties of Pr Doped Cerium Oxide Nanoparticles as a Solid Electrolyte for IT-SOFC Applications

Pure and Pr doped CeO2 nanoparticles were synthesized by citrate–nitrate auto combustion method. The XRD patterns of the prepared nanoparticles were found to be polycrystalline nature having cubic fluorite CeO2 structure. SEM images depicted all the samples exhibited flaky and porous structure with few large aggregates. FT-Raman studies showed the suppression of F2g peak in Pr doped CeO2 nanoparticles which indicated the increased oxygen vacancy concentration. UV-DRS spectra revealed the red shifting of absorption edge on Pr doping. The vibrational band assignment of pure and Pr doped CeO2 nanoparticles were analyzed by FT-IR spectroscopy. PL intensities of doped CeO2 nanoparticles decreased compared with pure CeO2 nanoparticles due to the evolution of non-radioactive oxygen vacancies in the structure. The variation of ionic conductivity as a function of temperature was studied using impedance spectroscopy for pure and Pr doped CeO2 nanoparticles. It was observed that the ionic conductivity of Pr doped CeO2 nanoparticles increased compared to pure CeO2 nanoparticles at the intermediate temperature.

Structural, optical and magnetic properties of Pr doped CeO2 nanoparticles synthesized by citrate–nitrate auto combustion method

In the present work, pure and Pr doped CeO2 nanoparticles in the form of Ce1−xPrxO2 (x = 0, 0.05, 0.10, 0.15 and 0.20) were synthesized by citrate–nitrate auto combustion method. The combustion derived products were annealed at 700 °C and characterized by X-ray diffraction (XRD) studies, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-diffuse reflectance spectroscopy (UV-DRS), Fourier transform-infrared spectroscopy (FT-IR), Fourier Transform-Raman Spectroscopy (FT-Raman), photoluminescence analysis (PL) and vibrating sample magnetometer (VSM) studies. XRD studies revealed that all the samples exhibited single phase cubic fluorite structure. SEM images displayed that pure and Pr doped CeO2 nanoparticles had irregular flaky shape with few agglomerations. TEM results show the proper formation of cubic fluorite structure of nanoparticles. UV-DRS spectroscopy results showed the red shifting in the absorption band edge with increased Pr concentration. The vibrational band assignment of pure and Pr doped CeO2 nanoparticles were analyzed by FT-IR spectroscopy. FT-Raman studies revealed increased defect concentration for the doped samples compared with pure CeO2. PL intensities of doped CeO2 nanoparticles decrease compared with pure CeO2 nanoparticles due to the evolution of non-radioactive oxygen vacancies in the structure. VSM results depicted the suppression of ferromagnetic behavior on Pr doping.

Rare Earth Yb3+ Doped Gd2O3 Single Phase Nanophosphors: Structural, Morphological and Photoluminescence Studies

In this paper, a report has been acclaimed on the structural, morphological and photoluminescence properties of the pure and Yb3+ (2, 5 and 10 wt %) doped gadolinium oxide nanophosphor, synthesized by the citrate-nitrate auto combustion method. The influence of doping concentration on the properties of the prepared phosphor was studied using different characterization techniques. Structural studies carried out using XRD revealed crystalline cubic phase for both the pure and doped Gd2O3 nanoparticles. The phase formation and purity were further confirmed from the FTIR spectra. Surface morphology was found using SEM analysis showed the clusters of tiny particles. Optical absorption measurements were recorded in the UV-Vis-NIR wavelength region and the optical band gap variations with dopant concentration were discussed. The probable mechanism for the visible PL emissions by Yb3+ doped Gd2O3 phosphors are explained by different transition phenomenon. Fluorescence lifetime along with energy transfer efficiency from Gd3+ to Yb3+ was determined.

Electrical modulus and dielectric behavior of Cr3+ substituted Mg–Zn nanoferrites

The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2−xO4; (0≤x≤0.025) nanoferrites synthesized citrate–nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4Hz–5MHz and 303–873K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε′), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

Improvement of physico-mechanical properties of Mg–Zn nanoferrites via Cr3+ doping

A series of Mg0.8Zn0.2CrxFe2−xO4 (0≤x≤0.025) nanoferrites were prepared by citrate–nitrate auto-combustion method. X-ray diffraction assured the formation of the ferrites in nanoscale and in single phase spinel structure. The magnetic and mechanical properties were investigated. All the elastic moduli values increase slowly and steadily with increasing Cr3+ content reaching the critical composition x=0.02. The magnetic parameters increased up to x=0.02 and then decreased with further Cr doping. Versatile applications were recommended owing to the porous nature of the nanoferrites.

Effect of addition of erbium stabilized bismuth oxide on the conductivity of lanthanum doped ceria solid electrolyte for IT-SOFCs

Nanosized powders of compositions, Bi0.8Er0.2O1.5 (ESB) and Ce0.85La0.15O1.925 (CLO) have been prepared using citrate–nitrate auto combustion method. ESB added CLO (ECLO) samples have been prepared by mixing nanosized CLO powder with 0.5, 1, 2 and 3wt.% of ESB. X-ray diffraction patterns confirm that all the samples are single phase having cubic fluorite structure similar to CeO2. Density of Ce0.85La0.15O1.925 increases with increasing ESB content. All the samples have been sintered at 1350°C. All the ECLO samples have density more than 97% of the theoretical value. Field emission scanning electron microscope images show dense microstructure with distinct grains and grain boundaries. Impedance measurements have been made in the temperature range 200–700°C in air. Addition of ESB increases the conductivity of the bulk as well as of grain boundaries. Ce0.85La0.15O1.925 with 0.5wt.% of ESB exhibits the maximum conductivity 1.41×10−2Scm−1 at 600°C of all the compositions. This value is one order of magnitude higher than the conductivity of Ce0.85La0.15O1.925 (1.99×10−3Scm−1).