Gel Combustion Synthesis Research Articles

Novel White Phosphor Bi3+ co-doped SrCeO3: 2 wt% Sm3+ Synthesized via Fuel Excess Gel Combustion Synthesis for wLED Applications.

Co-doping strategy is done if the emission from the activator is relatively low with existing excitation energy. Thus, to enrich the emission from an activator, the sensitizer like Bi3+ is co-doped onto the host and this intermediator transfers its emission energy to the activator. Prior to the study, no investigations had been conducted, marking the foundational exploration of the sensitizer effect within the rare earth-doped SrCeO3 matrix aimed at enhancing luminescence properties. The current study focuses on the innovation of single-phase robust white phosphors, SrCeO3: 2wt% Sm3+: xBi3+ (x = 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%) to coat near UV LED chips for high CRI wLED applications. The novel perovskites were synthesized using a low-temperature fuel excess gel combustion method, utilizing citric acid as the fuel and ammonium nitrate as an extra oxidizer. Upon co-doping SrCeO3: 2wt% Sm3+ with bismuth, the impact of changing sensitizer concentration on both the development of crystalline phases, morphology, elemental composition, band gap energy, and the luminescent properties of ceramic powders were explored through X-ray diffraction, FE-SEM, Energy dispersive spectra, UV-visible absorption spectra, and photoluminescence characterization methods. The experimental results revealed the orthorhombic single-phase formation of SrCeO3: 2wt% Sm3+: xBi3+perovskites yielding high crystallinity and luminescence maximum at critical sensitizer concentration 1 wt% Bi3+. Also, the bright white light emission of all the perovskites was confirmed using the CIE color diagram. Thus, nano-perovskite SrCe0.97Sm0.02O3: 1wt% Bi3+ acts as an inevitable direct phosphor coating the near UV chip in LEDs, which can be a great revolution in energy savings applications.

Soft sol–gel combustion synthesis: A potential route for functional nanocomposites of copper-based mixed valent oxides and cermet

The high reaction rate in the sol–gel combustion synthesis (SCS) often restricts precise control over the composition of mixed valent oxides in a single step. The current study overcomes this limitation by employing melamine—that forms a hydrogel with Cu(II)—as a novel fuel in the combustion synthesis. As opposed to the conventional SCS approach, the current synthesis occurs in a mild and controlled way under oxygen-lean conditions,wherein at and above 300 °C of calcination, a red-hot coke is found to form and persist for hours and hence termed as ‘soft sol–gel combustion synthesis’ (SSCS). Such a controlled synthesis is shown to be pivotal in obtaining a copper-based mixed-valent oxide/cermet nanocomposite system, comprising tunable levels of g-C3N4, in a single step. The phase compositions of the nanocomposites are modulated by varying calcination parameters like temperature and duration. These nanocomposites are thoroughly characterized for their microstructural, morphological, elemental, bandgap, and optical properties.Unique compositions are synthesized from the blend of Cu(II)–melamine complex gel with ZIF-8, in which formulations comprising different proportions of ZnO, CuO, Cu2O, metallic Cu and g-C3N4 have been obtained. Such multicomponent formulations post ball-milling exhibit notable photocatalytic activity in degrading organic pollutants and show high antibacterial efficacy against Escherichia coli under dark-light dual-mode conditions. Additionally, the SSCS approach has also been demonstrated for its versatility by synthesizing nickel-based cermet, which opens up numerous avenues for developing exotic material compositions for diverse applications in the realms of energy and environment.

Nano triumphs bulk in red light emission from Eu3+ doped Y2Zr2O7: Gel combustion versus solid state synthesis

Red phosphors are integral element of a phosphor converted white light emitting diodes (pc-WLEDs) which significantly impacts the color rendering index (CRI) and correlated color temperature (CCT) and thus provides a white light suitable for indoor applications. Red Light emitting Eu doped Y2Zr2O7 (YZOE) has been synthesized by two different synthesis methods viz. gel combustion (GC) and solid-state route (SS) wherein the former yielded nanocrystalline and latter leads to bulk YZOE. By virtue of lower light scattering, better electron-hole overlap integral and lower symmetric surrounding, nano YZOE displayed better photoluminescence properties in terms of emission intensity, photoluminescence quantum yield (PLQY) and excited state lifetime compared to its bulkier counterpart.

Thermoluminescence kinetics in beta-irradiated novel ZnGa2O4:Eu3+ phosphor produced via gel combustion synthesis

Eu3+ doped ZnGa2O4 phosphors with varying dopant concentrations were successfully synthesized using the combustion technique. X-ray diffraction analysis confirmed the consistency of both undoped and Eu3+ doped ZnGa2O4 samples with PDF#38–1240 card structure. The investigation of thermoluminescence (TL) characteristics involved studying TL glow curves in Eu3+ doped ZnGa2O4 samples with different dopant concentrations, employing various optical detection filter combinations. Among these, ZnGa2O4: 2%Eu3+ and the IRSL-TL wide blue band (wbb) proved to be the optimal sample and ideal detection filter pairing for identifying TL features. Following preheating experiments, the TL maximum was observed at around 190 °C, with a heating rate of 2 °Cs−1. The dose-response experiment for ZnGa2O4:2%Eu3+ exhibited satisfactory linearity, with a coefficient of b = 0.988 and an R2 value of 0.989 for doses up to 100 Gy. Moreover, for the dose range of 200–500 Gy, a sublinear relationship was maintained, with a coefficient of b = 0.31 and an R2 value of 0.988. Hoogenstraaten's method, along with the initial rise method and the Tm-Tstop experiment, was also employed in conjunction with a glow curve fitting package. This comprehensive approach facilitated the determination of the number of peaks, trap structure, and kinetic parameters within the thermoluminescence glow curve. Glow curve deconvolution using specialized software revealed the presence of five well-isolated and overlapping TL glow peaks, achieving a figure of merit (FOM) value of 1.39.

Al5BO9:Tb3+: Synthesis, structural characterization and thermoluminescence dosimetry studies for high intensity thermal neutron beams

In this manuscript, gel-combustion synthesis of Al5BO9:xTb3+ (x = 0.0%, 0.05%, 0.1%, 0.2% and 1.5%) phosphor along with the detailed structural characterizations using a host of techniques such as XRD, SEM, EDS, IR, EXAFS and PL etc. has been reported. XRD analysis confirmed the phase pure formation and also the nanocrystalline nature of the materials. Detailed EXAFS analysis explained the oxidation state and the coordination behaviour of Tb3+ ion in the Al5BO9 matrix. PL study showed that the material can be a potential green light emitting phosphor. Thermoluminescence (TL) study revealed the presence of a wide shoulder peak and a broad dosimetry peak situating at 551 K. Net TL response from 10B and 11B enriched Al5BO9:0.1%Tb3+ thin pellets showed prolonged linearity within the thermal neutron fluence range of 3.2 × 1010 to 1.6 × 1011 n/cm2. Also, the maximum fading of the TL signal is only 9% during the storage period of 112 days. These indicates that the developed material can be a potential candidate for dosimetry applications involving high intensity slow neutron beams. The TL glow curve was deconvoluted which revealed the presence of five individual peaks whose kinetic parameters viz. activation energy (E), order of kinetics (b) and frequency factor (s) were evaluated using both glow curve deconvolution and Chen's peak shape method and the results were found to be in good agreement.

Assessing the improved luminescence of SrCe1-xSmxO3 perovskite by concentration controlled extra oxidizer substitution

Strontium cerate perovskite nano phosphors when doped with rare earth elements show improved functional properties such as electrical conductivity and photoluminescence. Electrical conductivity investigations on doped strontium cerates have been studied widely over decades for application in electrochemical cells, hydrogen sensors, hydrogen extractors, etc. But only minimal research has been developed in the amelioration of photoluminescence in rare earth-doped strontium cerates. In the present study, samarium-doped strontium cerate perovskite nanophosphors were considered for utilization in optoelectronic applications. The perovskites SrCe1-xSmxO3 (x = 0.01,0.02,0.03) were prepared via a low-temperature gel combustion approach with citric acid as chelating agent and ammonia solution as an extra oxidizer. The influence of concentration variation on the evolution behaviour of the crystalline phase as well as the luminescence characteristics of ceramic powders are investigated using X-ray diffraction and Photoluminescence characterization techniques. Experimental results indicate that the calcinating temperature of 1223 K in gel combustion synthesis, much lower than the conventional solid-state reaction is only needed for the single-phase perovskite formation. Also, a comparison study of the luminescence behaviour by replacing internal constituent extra oxidizer ammonia solution with ammonium nitrate is observed in this study, and conditions for maximum luminescence intensity are hence discussed. The observed results on photoluminescence studies indicate that an enhancement in the luminescence intensity of SrCe0.98Sm0.02O3 occurred when we replaced extra oxidizer ammonia solution with ammonium nitrate. Thus, a bright orange-scarlet red emitting perovskite nano phosphor SrCe0.98Sm0.02O3 by the later technique can be synthesized and can act as an inevitable red phosphor coating the chip in LEDs, which can be a great revolution in energy savings applications.

Sol–Gel Combustion Synthesis and Study the High Frequency Dielectric Properties of Copper Ferrite Nanoparticles

Sol–Gel Combustion Synthesis and Study the High Frequency Dielectric Properties of Copper Ferrite Nanoparticles

Получение высокодисперсного порошка оксида цинка путем сжигания смеси нитрата цинка с глицином и его применение для фотокаталитического разложения фенола

The paper presents the results of a detailed study of the process and products of combustion during self-propagating high-temperature synthesis (SHS) of ZnO zinc oxide powder from mixtures of such common reagents as oxidizer zinc nitrate and reducing agent (fuel) glycine, as well as the application of synthesized highly dispersed submicron and nanosized ZnO powder for the phenol photocatalytic decomposition under the action of ultraviolet irradiation. An aqueous solution of a mixture of reagents (the SHS-S process or Solution Combustion Synthesis – SCS) and the gel from a mixture of initial dry reagents formed when they were moistened due to hygroscopicity (the SHS-G process or Gel Combustion Synthesis – GCS) were combusted. The authors studied the phase and chemical compositions, the structure of the combustion product, and the effect of calcination in an oxidizing air medium and grinding in drum ball and planetary-centrifugal mills, as well as in mortar, on them and their photocatalythic activity. The study showed that calcination considerably increases the photocatalytic activity of combustion products due to a significant decrease in carbon impurity in the unburned fuel remains, and grinding in mills reduces the photocatalytic activity due to iron contamination and coarsening of ZnO particle agglomerates. The difference between the photocatalytic activity of the SHS-G and SHS-S products in the phenol decomposition is evident only at the initial stage of ultraviolet irradiation, after which this difference disappears. The authors discuss the direction of further research to increase significantly the photocatalytic activity of zinc oxide synthesized during combustion to use it effectively for the phenol decomposition under the action of visible light.

Perovskite GdAlO3:Dy3+ nanophosphors: A gel-combustion synthesis, phase evaluation and down conversion luminescent characteristics for lighting applications

The single phase Gd1-xAlO3:xDy3+ (x = 1, 3, 5, 7, 9 mol %) nanophosphors that produce cool white light have been synthesized by utilizing urea assisted gel-combustion synthetic method. The prepared nanocrystalline materials are thoroughly investigated using a variety of structural as well as photophysical analyses. According to Rietveld refinement elucidations, pure GdAlO3 and Dy3+ doped GdAlO3 nanomaterials have crystallized into an orthorhombic structure with space group of Pnma. Transmission electron microscopy (TEM) graph validates that agglomerated particle with irregular dimensionality are still in nano-range which corroborate the outcomes of diffraction data. As a result of effective energy transfer between Gd3+ to Dy3+, Dy3+ emission achieved by Gd3+ excitation at 281 nm was substantially greater than that obtained through direct excitation of Dy3+ at 350 nm. The photoluminescence emission spectra recorded at 281 nm excitation wavelength revealed two strong bands i.e. blue and yellow which were accompanying the transitions 4F9/2 → 6H15/2 (481 nm) and 4F9/2 → 6H13/2 (575 nm), separately. The dipole-quadruple interactions are accountable for quenching of concentration in focused nanophosphors. Photometric analysis exposed the luminescence of white color in prepared nanomaterials demonstrating its extensive applications in white light applications.

One-step CoFe2O4 gel combustion synthesis using tris(hydroxymethyl)aminomethane (TRIS) as alternative fuel: Control of oxidiser-to-fuel molar ratio for tuning its structural, magnetic, and optical properties

Spinel ferrites are promising candidates for various applications as transformers, transducers, inductors in the electronic field, sensors, biosensors and hyperthermia agents in the biomedical field. Combustion synthesis, as a method for obtaining ferrites, is gaining attention. However, most fuels generate high ignition temperatures, which lead to larger (micrometric) crystallites or even render combustion synthesis unfeasible in a single step. Spinel cobalt ferrite (CoFe2O4) has unique features that facilitate tuning the spinel structure based on modifications in the synthesis parameters. In this study, CoFe2O4 was synthesised via gel combustion using tris(hydroxymethyl)aminomethane (tris) as an alternative fuel. The effect of the oxidizer-to-fuel molar ratio (Ψ) on their formation and structural, optical, and magnetic properties were evaluated. Gels were prepared from metal nitrates and tris at Ψ values of 0.6, 0.8, 1.0, 1.2, and 1.4. Thermal analysis of the ignition temperature was found to be dependent on Ψ. The adiabatic flame temperatures were estimated using thermodynamic calculations, as 2688.36 K when Ψ = 0.6, and 1017.56 K when Ψ = 1.4, which indicates that the temperatures would be sufficient to form the phase in one step without additional thermal treatment. X-ray diffraction confirmed the formation of CoFe2O4 as a single-phase for all Ψ values. Raman and Fourier transform infrared spectroscopy confirmed the formation of CoFe2O4 for all Ψ values investigated. The low bandgap values (0.92–1.36 eV) suggest several promising applications in photoactivated materials. The magnetic properties of the as-prepared powders measured by a vibrating sample magnetometer revealed saturation magnetisation values, Ms, and coercivity field, Hc, and remanence magnetisation were dependant on Ψ. These results show that tris can be used as a fuel to synthesise spinel ferrites via one-step gel combustion with excellent properties for several applications.

Sol–gel combustion synthesis and photocatalytic dye degradation studies of rare earth element Ce substituted Mn–Zn ferrite nanoparticles

This paper reports the impacts of cerium (Ce) substitution on morphological, magnetic and structural characteristics of Mn0.5Zn0.5CexFe2-xO4 (x = 0.0, 0.3 and 0.5) ferrites nanoparticles (NPs) prepared via sol gel combustion method. The crystalline structure, magnetic and morphological features were examined by powder X-ray diffraction, vibrating sample magnetometer and scanning electron microscope analyser individually. Magnetic hysteresis (M−H) loops of samples were determined to examine the magnetic properties of synthesized samples. Magnetic measurement shows that samples exhibit ferromagnetic behaviour at room temperature (RT). The magnetic properties are described in terms of cation substitution and grain size effect. The various concentration of synthesized photocatalyst such as Mn0.5Zn0.5Fe2O4, Mn0.5Zn0.5Ce0.3Fe1.7O4 and Mn0.5Zn0.5Ce0.5Fe1.5O4 NPs were analysed under visible light irradiation by the degradation of an aqueous solution of Congo red and Reactive Orange 16 dyes and the sample Mn0.5Zn0.5Ce0.3Fe1.7O4 NPs showed higher degradation percentage 97.25% and 98.42% respectively, than other compositions at 120 min with enhanced visible light absorption range. These performances expose that these nanomaterials are appropriate for high frequency applications.

Optimization of sol–gel combustion synthesis of calcium looping CO2 sorbents, Part Ⅱ: Effects of thermal activation conditions

This work is the extension of part Ⅰ. The last procedure in the technical route of sol–gel combustion synthesis for CaO sorbents preparation, i.e. the thermal activation process was studied. The effects of the relevant preparation parameters including temperature, duration, and heating rate on the cyclic CO2 sorption performance, micromorphology, pore size distribution, and physical parameters of the prepared pure CaO sorbents were investigated. Results were obtained that high temperature (>950 ℃), long duration (>1 h), and low heating rate (<2 ℃/min) in the thermal activation process accelerated the formation of a stable structure in CaO sorbents. Accordingly, the sorbent showed low initial conversion, an opposite increasing trend in the first several cycles, and high cyclic stability. The optimal thermal activation condition was 850 ℃ for 5 min without heating rate. Furthermore, by integrating the optimization results of the whole technical route, the optimal CaO sorbent was prepared, which showed excellent performance. With the cyclic condition of 10 minutes of carbonation at 650 ℃ under 15% volume CO2 and 10 minutes of calcination at 850 ℃ under 100% volume N2, its carbonation conversion varied from 98.2% to 52.1% through 50 cycles. An average enhancement of 21.8% in 50 cycles was obtained compared to the sorbent before optimization and the average enhancement was 168.3% compared to CaCO3. Moreover, the pH value of the precursor solution was the most influential factor among the preparation variables.

P123 Assisted Sol- Gel Combustion Synthesis of Mesoporous Strontium Titanate Nanomaterials for Photocatalytic Degradation of Methylene Blue

We have reported the synthesis of strontium titanate (ST) nanomaterials via sol-gel combustion method in the presence and absence of pluronic P123 as a templating agent and citric acid as fuel at relatively high temperature. The presence of templating agent and fuel helps to generate mesoporosity in the materials resulting in mesoporous strontium titanate (MST). The materials are well characterized by various instrumental techniques. X-ray powder diffraction analysis has confirmed that both of the strontium titanate materials exhibited cubic perovskite structure. The FT-IR spectra has indicated that during high temperature calcination, carbonate species expelled out from the decomposition of the volatile impurities get adsorbed on the surface of titanate nanostructure, which is predominant in MST as indicated by the variation in the intensity of peak in between 1450 cm-1 –1470 cm-1. From diffuse reflectance spectra, the absorption edge of the MST is extended to visible regions and showed band gap energy of 3.14 eV compared to 3.21 eV for ST. The reduction in intensities of PL emission bands in MST compared to ST has indicated that slow electron-hole recombination takes place in this material compared to ST. The Transmission electron microscopic studies reveal the formation of spherical and cuboidal nanostructures with an average size of 55 and 38 nm for ST and MST material, respectively. From N2 sorption studies, the MST exhibit type IV adsorption isotherms with H3 type hysteresis loop indicated the formation of mesoporosity in this material whereas the ST indicated the formation of type II adsorption isotherms typical of nonporous materials. The elemental analysis of MST material is further confirmed from X-ray photoelectron spectroscopic analysis and confirm the formation of carbonate species on the surface of the materials. The photocatalytic activity of the materials is elucidated by the degradation of methylene blue under UV light irradiation and degradation followed first order kinetics with Langmuir-Hinshelwood adsorption pathways. The activity of MST material is found to be 5 times faster than ST at similar experimental conditions. The enhanced activity of the MST might be attributed to, lower band gap energy, presence of carbonate species, and lower electron-hole recombination in this material.

Electromagnetic wave absorption properties of Pr1-xBaxMnO3 ceramics prepared by a sol–gel combustion method

Manganese-based rare-earth perovskite oxides with excellent dielectric loss and effective magnetic loss have attracted considerable attention as microwave-absorbing materials. Herein, irregular spherical particles of Pr1-xBaxMnO3 (x = 0, 0.02, 0.04, 0.06) were successfully designed and fabricated by a sol–gel combustion method. The Ba2+ doping amount played a dominant role in adjusting the electromagnetic (EM) functions of the PrMnO3 ceramics. X-ray diffraction and refinement results illustrated that Ba2+ doping had no effect on the main phase of PrMnO3, but it caused lattice distortion and led to changes in the lattice constant of the material. The magnetisation curves did not reach saturation, and the materials had low coercivity at room temperature. Fluctuations in the Mn4+/Mn3+ ratio due to oxygen vacancies decreased owing to the addition of Ba2+, as demonstrated by the X-ray photoelectron spectroscopy analysis. It was observed that the absorption of electromagnetic wave (EMW) energy could be effectively controlled by adjusting the Ba2+ content. The Pr0.98Ba0.02MnO3 sample exhibited the best EMW absorption ability; the minimum reflection loss (RLmin) was -46.45 dB (absorption rate of 99.99%), and the matching thickness was 3.7 mm. The maximum bandwidth of the Pr0.98Ba0.02MnO3 sample was 6.16 GHz, while the thickness of the absorbing coating was only 2.5 mm. When d = 5.5 mm, Pr0.94Ba0.06MnO3 achieved an RL of -18.97 dB at 5.04 GHz (C band). This shows that Pr0.94Ba0.06MnO3 also has good microwave absorption ability in the low-frequency C band, and its RL peak conformed to the nλ/4 cancellation law at a given thickness. The results show that the low-cost sol–gel combustion synthesis process and lightweight, wideband, and strong absorption ability of Pr1-xBaxMnO3 make it a promising candidate for microwave absorbers.

Evaluating the Activity and Stability of Perovskite LaMO3-Based Pt Catalysts in the Aqueous Phase Reforming of Glycerol

The aqueous phase reforming of glycerol, to hydrogen, alkanes and liquid phase dehydration/dehydrogenation products, was studied over a series of 1 wt% Pt/LaMO3 (where M = Al, Cr, Mn, Fe, Co, Ni) catalysts and compared to a standard 1 wt% Pt/γ-Al2O3 catalyst. The sol–gel combustion synthesis of lanthanum-based perovskites LaMO3 produced pure phase perovskites with surface areas of 8–18 m2g−1. Glycerol conversions were higher than the Pt/γ-Al2O3 (10%) for several perovskite supported catalysts, with the highest being for Pt/LaNiO3 (19%). Perovskite-based catalysts showed reduced alkane formation and significantly increased lactic acid formation compared to the standard catalyst. However, most of the perovskite materials undergo phase separation to LaCO3OH and respective M site oxides with Pt particle migration. The exception being the LaCrO3 support which was found to remain structurally stable. Catalytic performance remained stable over several cycles, for catalysts M = Al, Cr and Ni, despite phase separation of some of these materials. Materials where M site leaching into solution was observed (M = Mn and Co), were found to be catalytically unstable, which was hypothesised to be due to significant loss in support surface area and uncontrolled migration of Pt to the remaining support surface. In the case of Pt/LaNiO3 alloying between the exsoluted Ni and Pt was observed post reaction.

Superparamagnetic MnFe2O4 Ferrite by Gel Combustion Synthesis Using TRIS as a Fuel: Influence of Oxidizer to Fuel Ratio

Superparamagnetic MnFe2O4 Ferrite by Gel Combustion Synthesis Using TRIS as a Fuel: Influence of Oxidizer to Fuel Ratio

Synthesis, Characterization and sintering of nanocrystalline (U1-yCey)O2±x

Nanocrystalline solid solutions of (U1-yCey)O2±x [y = 0.15, 0.22, 0.28, 0.35] have been synthesized by citrate gel-combustion route with a fuel to oxidant ratio of 1. The “as prepared” powders were calcined at 873 K in air for 6 h and were consolidated into pellets at 220 MPa. These green pellets were reduced at 1073 K under flowing hydrogen for 8 h and were sintered at 1873 K under flowing Ar+8% H2 for 6 h. All these powders were characterized for their X-ray crystallite size (XCS), specific surface area (SSA), particle size distribution (PSD), porosity, bulk density (BD) and residual carbon (RC). The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), respectively. The Hall–Williamson analysis of the X-ray diffraction (XRD) data revealed that the “as-prepared” powders consist of nano grains with a size of about 10 to 20 nm and the results have been substantiated by bright field HRTEM image analysis of these samples. These sintered pellets were characterized for their phase composition, density and microstructure. Presence of a single phase fluorite solid solution was confirmed by XRD. A sintered density of 95.88±0.62% of theoretical density (TD) could be achieved. A systematic study on the gel-combustion synthesis of nanocrystalline (U1-yCey)O2±x [y = 0.15, 0.22, 0.28, 0.35] powders is being reported for the first time.

Structural and luminescence characterization of Ce3+ and Mn2+ co-activated zinc silicate nanocrystal obtained by gel combustion synthesis

The structural, morphological, and luminescence properties, including photoluminescence (PL) and thermoluminescence (TL), of newly produced Zn2SiO4 co-activated by Ce3+ and Mn2+ ions using the gel-combustion synthesis, are investigated in deep. To determine the co-dopant effect precisely, non-doped, Ce3+ doped, and Ce3+ and Mn2+ double doped Zn2SiO4 phosphors are evaluated. The fluorescence decay curves indicate that a shorter decay time at relatively high Mn concentrations takes place. The TL glow curve readouts observed by applying the dose range between 0.1 and 2000 Gy after 150 °C preheat are performed at a linear heating rate of 2 °C/s from room temperature (RT) to 500 °C. An anomalous heating rate behavior is observed when the influence of different heating rates on TL characteristics is reported. An excellent agreement is found between the TL kinetic parameters analyzed by the initial rise (IR) with TM–Tstop analysis and computerized glow curve deconvolution (CGCD) methods.

Evaluation of the Microstructure and the Electrochemical Properties of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] Electrolytes for IT-SOFCs

The influence of copper addition (0.5–2 mol%) on the crystal structure, densification microstructure, and electrochemical properties of Ce0.8Gd0.2O1.9 synthesized in a one-step sol–gel combustion synthesis route has been studied. It has been found that Cu is very active as sintering aids, with a significative reduction of GDC firing temperature. A reduction of 500 °C with a small amount of copper (0.5 mol%) was observed achieving dense bodies with considerable ionic conductivities. Rietveld refined was used to investigate the crystal structure while relative density and microstructural examination were performed in the sintering temperature range of 1000–1200 °C after dilatometer analysis. High dense bodies were fabricated at the lowest sintering temperature, which promotes the formation of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] solid solution and the absence of secondary phase Cu-rich or the segregation or copper at the grain boundary. As compared to the pure GDC an improvement of total conductivity was achieved with a maximum for the highest copper content of 2.23·10−3–9.19·10−2 S cm−1 in the temperature range of 200–800 °C.

Probing structural evolution in thorium–cerium mixed oxides thermally annealed in oxidizing and reducing conditions

ThO2 is a promising matrix either for incineration or direct disposal of plutonium and (Th, Pu)O2 is a potential advanced fuel. In this view, a ThO2–CeO2 mixed oxide system has been investigated under oxidizing as well as reducing conditions wherein CeO2 has been employed as a non-radioactive surrogate for PuO2. Selected compositions in Th1−xCexO2 (0 ≤ x ≤ 0.5) series were prepared by gelcombustion synthesis and thoroughly characterized by XRD and Raman spectroscopy. Both the studies confirm the formation of a fluorite-type (F-type) solid solution throughout the series after calcination of gelcombusted powders at 873 K in air. The F-type phase is retained even on annealing these solid solutions at an elevated temperature 1773 K in air. Lattice parameter of the F-type phase decreases as a function of ceria content in accordance with the Vegard’s law. On the contrary, the position of the F2g Raman band in these solid solutions exhibits non-ideal behavior. Annealing of calcined samples at 1873 K in a reducing atmosphere (Ar−8% H2) yields a single phase of F-type structure at x ≤ 0.2, while a biphasic phase field at x ≥ 0.3. Characteristic Raman vibration bands have been utilized to identify the presence of possible defects (due to Ce4+/Ce3+ substitution in ThO2) that are otherwise difficult to detect by the XRD studies. Detailed structure and defect analysis in ThO2–CeO2 mixed oxides will not only give valuable insight to the fuel designer but also bring out fundamental chemical aspects of such mixed oxides.