O3 Solid Solutions Research Articles

Effect of lithium substitution with sodium on electrical properties in La0.5Li0.5-xNaxTiO3 and La0.67Li0.2-yNayTi0.8Al0.2O3 solid solutions

Li-containing La0.5Li0.5-xNaxTiO3 and La0.67Li0.2-yNayTi0.8Al0.2O3 solid solutions have been obtained by solid-state reaction route that involves chemical decomposition reactions. Complex impedance spectroscopy measurements demonstrate that the electrical properties in La0.5Li0.5-xNaxTiO3 and La0.67Li0.2-yNayTi0.8Al0.2O3 systems depend on different areas of the ceramic's grain and can be represented by the equivalent circuit consisting of two (when x = 0.5, y = 0.2) and three series-connected elements (0 ≤ x ≤ 0.4, 0 ≤ y ≤ 0.15). It has been shown that an increase in sodium concentration leads to a decrease in the ceramic's grain size for La0.5Li0.5-xNaxTiO3 and La0.67Li0.2-yNayTi0.8Al0.2O3 solid solutions. Substitution of lithium ions by sodium leads to an increase in the unit cell volume of the perovskite structure. It has been demonstrated that La0.67Li0.14Na0.06Ti0.8Al0.2O3 and La0.5Li0.4Na0.1TiO3 materials with low sodium concentration have the maximum value of dielectric constant.

Growth of BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 Solid Solution Photocatalyst for Visible Light-Driven Z-Scheme Overall Water Splitting

BaTaO 2 N with intense visible light absorption has been demonstrated as a promising photocatalyst for Z-scheme overall water splitting, whereas the photocatalytic activity of BaTaO 2 N is still restricted by strong charge recombination at structural defects. Here, we present the direct growth of BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution from a lattice-matched BaNa 0.25 Ta 0.75 O 3 precursor through volatilization of Na species during a nitridation process. This method promotes the direct phase transformation from BaNa 0.25 Ta 0.75 O 3 to BaTaO 2 N to inhibit the formation of defect states. As a result, the as-obtained BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution shows greatly enhanced activity compared to the conventional BaTaO 2 N, regardless of photocatalytic H 2 evolution in the presence of methanol or Z-scheme overall water splitting. This study provides a facile method to construct (oxy)nitride-based solid solution photocatalysts with low defect density for efficient solar hydrogen production from water splitting.

Extreme structural stability of Ti0.5Sn0.5O2 nanoparticles: synergistic effect in the cationic sublattice.

Ti0.5Sn0.5O2 nanoparticles (∼5 nm and ∼10 nm) have been studied under high pressure by Raman spectroscopy. For particles with diameter ∼10 nm, a transformation has been observed at 20-25 GPa while for particles with ∼5 nm diameter no phase transition has been observed up to ∼30 GPa. The Ti0.5Sn0.5O2 solid solution shows an extended stability at the nanoscale, both of its cationic and anionic sublattices. This ultrastability originates from the contribution of Ti and Sn mixing: Sn stabilizes the cationic network at high pressure and Ti ensures a coupling between the cationic and anionic sublattices. This result questions a "traditional" crystallographic description based on polyhedra packing and this synergistic effect reported in this work is similar to the case of metamaterials but at the nanoscale.

Synthesis of n-type ZrO2 doped ε-Ga2O3 thin films by PLD and fabrication of Schottky diode

Tin-assisted pure phase n-type ZrO2-doped ε-Ga2O3 films were synthesized by pulsed laser deposition (PLD) and deposited on (0001) epi-GaN/sapphire substrates. The characterization of n-type ZrO2-doped ε-Ga2O3 thin films and the electrical properties of SBD based on that film were investigated in details. From XRD, the pure Zr-doped ε-Ga2O3 without diffraction peaks of zirconia suggested the formation of ε-(ZrxGa1−x)2O3 solid solution. The surface morphology and chemical content of the ε-Ga2O3 thin film were studied by AFM and XPS. The electrical resistivity and related free carrier concentration at room temperature were measured to be 108 Ω·cm and 5.5 × 1015 cm−3, respectively, and mobility up to 10.3 cm2/V·s. The Schottky barrier diode possessed a rectification ratio up to 106~107, breakdown voltage of 392 V, and the interface states density from 2.4 × 1013 cm-2 eV-1 to 6.4 × 1014 cm-2 eV-1 with the trap energy level from 0.89 eV to 0.94 eV below the bottom of the conduction band.

Growth, Structure, and characterization of new High-TC Piezo-/Ferroelectric Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals

In this work, new bismuth-based complex perovskite piezo-/ferroelectric single crystals of the (1-x)PbTiO3-xBi(Zn2/3Ta1/3)O3 solid solution have been successfully grown by the high temperature solution method (HTSG). The crystal structure was found to be tetragonal at room temperature by means of structural analysis by X-ray diffraction and domain examination by polarized light microscopy (PLM). High Curie temperature (TC = 470 °C) was determined by dielectric measurements and PLM observations. Band-like domain structures were observed in the (001)-oriented single crystal with a width of 100–200 µm. Good piezoelectric performance (d33 = 251 pC/N) and high coercive field (EC = 30 kV/cm) were found by the piezoelectric and ferroelectric characterizations. Detailed crystal structural refinement was performed to establish the structure–property relationship in this system. Comparative studies of current bismuth-based complex perovskite solid solution single crystals point to the advantages of the Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals in terms of high TC, good piezoelectric performance, and high coercive field. These advantages make this piezo-crystal system a favourable candidate for potential high-temperature and high-power electromechanical applications.

Solid-State Dispersions of Platinum in the SnO2 and Fe2O3 Nanomaterials.

The dispersion of platinum (Pt) on metal oxide supports is important for catalytic and gas sensing applications. In this work, we used mechanochemical dispersion and compatible Fe(II) acetate, Sn(II) acetate and Pt(II) acetylacetonate powders to better disperse Pt in Fe2O3 and SnO2. The dispersion of platinum in SnO2 is significantly different from the dispersion of Pt over Fe2O3. Electron microscopy has shown that the elements Sn, O and Pt are homogeneously dispersed in α-SnO2 (cassiterite), indicating the formation of a (Pt,Sn)O2 solid solution. In contrast, platinum is dispersed in α-Fe2O3 (hematite) mainly in the form of isolated Pt nanoparticles despite the oxidative conditions during annealing. The size of the dispersed Pt nanoparticles over α-Fe2O3 can be controlled by changing the experimental conditions and is set to 2.2, 1.2 and 0.8 nm. The rather different Pt dispersion in α-SnO2 and α-Fe2O3 is due to the fact that Pt4+ can be stabilized in the α-SnO2 structure by replacing Sn4+ with Pt4+ in the crystal lattice, while the substitution of Fe3+ with Pt4+ is unfavorable and Pt4+ is mainly expelled from the lattice at the surface of α-Fe2O3 to form isolated platinum nanoparticles.

Ti0.8B0.1P0.1O2 Solid Solution with the Anatase Structure

Ti0.8B0.1P0.1O2 Solid Solution with the Anatase Structure

Structural and Magnetic Phase Transitions in the Fe-Rich Compositional Range of the Multiferroic BiFe1- x [Zn0.5Ti0.5] x O3 Perovskites

The (1-x)BiFeO3-xBiZn0.5Ti0.5O3 solid solutions (0.05 ≤ x ≤ 0.25) were prepared using high-pressure synthesis. Up to 25 at.% substitutions of Fe by the combination of [Mg0.5Ti0.5] were found to increase the unit cell volume of the primitive perovskite cell, while the crystal structure remains the rhombohedral perovskite, as that in the parent BiFeO3. With increasing temperature, the as-prepared ceramics of the x = 0.25 composition reversibly transform into a cubic modification between about 970 and 1070 K. However, this phase transition is overlapped with a gradual decomposition of the perovskite phase, which starts above 770 K. The perovskite phase with the substitution rate corresponding to x = 0.25 is antiferromagnetic below T N∼460 K. Peculiarities of the temperature-dependent magnetic behavior of this composition at about 220 and 315 K, which might indicate transitions between the states with different magnetic orderings, have been observed.

Production of light hydrocarbons at atmospheric pressure from CO2 hydrogenation using CexZr(1-x)O2 iron-based catalysts

Considering that the combination of ZrO2 and CeO2 have superior catalytic properties compared to the individual oxides, the present work investigates the production of light hydrocarbons by carbon dioxide hydrogenation at atmospheric pressure, using iron catalysts constituted of CexZr(1-x)O2 solid solutions (x = 0, 0.25, 0.5, 0.75, and 1). The aim was to determine the effect of the composition of the CexZr(1-x)O2 oxides on the reaction. The materials were characterized by XRF, XRD with Rietveld refinement, textural analysis, Raman spectroscopy, H2-TPR, H2-TPD, and CO2-TPD. The catalysts were tested in the CO2 hydrogenation reaction at 370 °C, under atmospheric pressure, using a molar ratio H2/CO2 = 3, for at least 5 h of time on stream. For the iron-based catalysts constituted of CeO2 and/or ZrO2, the CO2 conversion and selectivity towards the light olefins first increased as the Zr content increased, reaching the highest values with the iron catalyst supported on the material containing 50 % of Ce and 50 % of Zr (molar concentrations on an oxygen-free basis), and then decreased at higher Zr concentrations. The highest CO2 conversion achieved with this catalyst could be attributed to the quantity of basic sites. An appropriate balance between the amounts of adsorbed CO2 and H2 could provide a suitable surface C/H concentration ratio, leading to the best products distribution.

High-Temperature Chemical Stability of Cr(III) Oxide Refractories in the Presence of Calcium Aluminate Cement.

Al2O3-CaO-Cr2O3 castables are used in various furnaces due to excellent corrosion resistance and sufficient early strength, but toxic Cr(VI) generation during service remains a concern. Here, we investigated the relative reactivity of analogous Cr(III) phases such as Cr2O3, (Al1−xCrx)2O3 and in situ Cr(III) solid solution with the calcium aluminate cement under an oxidizing atmosphere at various temperatures. The aim is to comprehend the relative Cr(VI) generation in the low-cement castables (Al2O3-CaO-Cr2O3-O2 system) and achieve an environment-friendly application. The solid-state reactions and Cr(VI) formation were investigated using powder XRD, SEM, and leaching tests. Compared to Cr2O3, the stability of (Al1−xCrx)2O3 against CAC was much higher, which improved gradually with the concentration of Al2O3 in (Al1−xCrx)2O3. The substitution of Cr2O3 with (Al1−xCrx)2O3 in the Al2O3-CaO-Cr2O3 castables could completely inhibit the formation of Cr(VI) compound CaCrO4 at 500–1100 °C and could drastically suppress Ca4Al6CrO16 generation at 900 to 1300 °C. The Cr(VI) reduction amounting up to 98.1% could be achieved by replacing Cr2O3 with (Al1−xCrx)2O3 solid solution. However, in situ stabilized Cr(III) phases as a mixture of (Al1−xCrx)2O3 and Ca(Al12−xCrx)O19 solid solution hardly reveal any reoxidation. Moreover, the CA6 was much more stable than CA and CA2, and it did not participate in any chemical reaction with (Al1−xCrx)2O3 solid solution.

Diffused phase transition boosted dye degradation with Ba (ZrxTi1−x)O3 solid solutions through piezoelectric effect

Micron-sized Ba(Zr x Ti 1−x )O 3 particles have been prepared using the conventional solid state method, and their microstructure, morphology and piezocatalytic properties have been investigated in detail. The present study shows that Ba(Zr 0.05 Ti 0.95 )O 3 is a relaxor-like ferroelectric having a typical perovskite structure with existence of polar nanodomain regions at room temperature. With the increase of the degree of diffuseness γ, the piezoelectric properties increased. Also, the particles exhibit good piezocatalytic performance in degrading organic pollutants with the aid of ultrasonic vibration. The catalytic activity can be significantly improved by poling, i.e. the alignment of polarization using an applied electric field. The catalytic degradation ratio of RhB, MB and MO dyes for poled Ba(Zr 0.05 Ti 0.95 )O 3 particles is reached ~95%、~70% and ~65% after 90 min, respectively. Our results also reveal that the existence of polar nanodomain due to the diffuse phase transition can highly boost the catalytic activity of the Ba(Zr 0.05 Ti 0.95 )O 3 particles, which can be used as multifunctional catalyst for degrading organic pollutions. • The diffuse phase transition can enhance the piezocatalytic activity. • The polar nanodomains are responsible for high piezocatalytic performance. • The polar nanodomains can induce local polarization and inhomogeneity. • Micron-sized Ba(Zr 0.05 Ti 0.95 )O 3 particles display RhB degradation of 95%.

Fundamental understanding on the microstructure and corrosion resistance of Cr-(Cr, Al)2O3 composite coatings in-situ synthetized by reactive plasma spraying

Three composite coatings were prepared with Al-Cr2O3-Al2O3 composite powders feedstocks by in-situ reactive plasma spraying, and the microstructures and corrosion resistances were studied. The results show that the CAC-1 coating is the hypoeutectic microstructure consisting of large-size Cr particles and the eutectic structure, the CAC-2 coating presents a typical eutectic microstructure [nano-Cr + (Cr, Al)2O3], and the CAC-3 coating is the hypereutectic microstructure which is composed of (Cr, Al)2O3 solid solution and eutectic structure. The corrosion resistance of the coating is closely related to the microstructure and defects of the coating. The surface of the nano-Cr particles in the CAC-2 coating can form a stable Cr(OH)3 film, which hinders the further contact with the electrolyte, thereby improving the corrosion resistance of the coating itself. In addition, the uniform and dense microstructure also leads to the least coating defects, further improving the corrosion resistance of the coating. While the surface product film of large-size Cr particles in the CAC-1 coating cannot exist stably, causing the Cr to continue to dissolve until it peels off. The coating itself has the highest porosity, so the coating has the worst corrosion resistance. The CAC-3 coating mainly exhibits the characteristics of ceramic coating due to the limited eutectic structure contained. Due to the unevenness of the microstructure, the coating has more defects, resulting in lower corrosion resistance than the CAC-2 coating.

Static and dynamic corrosion behavior of SnO2‐doped AZS slip cast refractory in SLS glass

AbstractThe corrosion behavior of a tin IV oxide‐doped AZS‐refractory, subject to static and dynamic corrosion testing at 1370˚C in soda‐lime‐silica glass, was studied considering the effect of the microstructural features on corrosion. The refractory was synthesized by slip cast methods through reaction sintering of alumina and zircon raw materials using SnO2 as a sintering agent. SnO2 had a considerable influence in the enhanced alumina/zircon reaction sintering and the subsequently evolved microstructures of an interlocked Zr(1‐x)Sn(x)O2 solid solution reinforced alumina‐mullite composite. The process kinetics of the refractory corrosion followed reasonably well the predicted dependence on the square root of angular velocity under forced convection corrosion. Glass chemical corrosion and erosion of the refractory, under static and dynamic glass conditions, respectively, revealed the Zr(1‐x)Sn(x)O2 solid solution‐rich mullite matrix as providing the most corrosion resistance and glass compatibility.

Remarkably enhanced photocatalytic H2 evolution via construction of Ti0.5Ru0.5O2/TiO2(B)/TiO2(A) three-phase-junctions

TiO2 is an important material used in photocatalytic H2 evolution. Here nanosheets with a Ti0.5Ru0.5O2/TiO2(B)/TiO2(A) three-phase-junctions, composed of solid solution rutile phase Ti0.5Ru0.5O2, bronze phase TiO2(B), and anatase phase TiO2(A), are constructed via a hydrothermal method and subsequent calcination. At the optimal calcination temperature of 350 °C, the highest H2 evolution rate reaches 27.817 mmol∙g−1∙h−1 at 25 °C, which is further increased up to 62.357 mmol∙g−1∙h−1 at 70 °C by synergistic photothermal catalysis. The photocatalytic activity of the optimized catalyst was further enhanced by loading with Pt as a co-catalyst. It is found that, in addition to helping charge separation, migration, and inhibiting the charge recombination, the three-phase-junctions structure is a key to present strong oxidation and reduction ability. Ti0.5Ru0.5O2 solid solution has excellent co-catalytic ability, much better than Ru oxide, metallic Ru, as well as Pt. It works as hole acceptor, accelerating the generation and quench of photo induced peroxyl radicals, and thus significantly enhancing the H2 generation rate.

Studying of dielectric spectra of YCu0.15Mn0.85O3 solid solution with the use of complex conductivity

This work presents the results of studying the electrophysical properties of the [Formula: see text][Formula: see text]O3 solid solution in the range of temperatures of [Formula: see text] = 26–400[Formula: see text]C and frequency range of [Formula: see text] = 102–105 Hz. A model description of the revealed dispersion of dielectric parameters in the material is made. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity was used as an approximation model. It is shown that the application of this model almost exactly describes the frequency behavior of the dielectric constant [Formula: see text]/[Formula: see text]( [Formula: see text], the dielectric loss tangent tg[Formula: see text]( [Formula: see text] as well as the real and imaginary parts of complex conductivity [Formula: see text]( [Formula: see text] and [Formula: see text]( [Formula: see text]. The results of this work are an important step in identifying the opportunities and understanding the applications of this model.

Corrigendum: Dielectric Properties of BaZr0.2[Ti(1-x)Mgx/3Ta2x/3]0.8O3 Solid Solution

The title of the original article was "Ferroelectric and Dielectric properties of BaZr0.2[Ti(1-x)Mgx/3Ta2x/3]0.8O3 solid solution".However, the title can be misleading to the readers since the ferroelectric study was not performed in detail. Hence the title of the article is modified as "Dielectric properties of BaZr0.2[Ti(1-x)Mgx/3Ta2x/3]0.8O3 solid solution"

(Sn,Ti,Nb)xO2 Solid Solution: An Innovative Nanostructured Material and Its Chemoresistive Properties

Introduction Recently, great attention has been paid to solid solutions and composite materials based on metal oxides in order to obtain nanostructures with enhanced sensing performance with respect to those of single-oxide counterparts [1]. Tin and titanium dioxides (SnO2 and TiO2) are wide-gap n-type semiconductors extensively investigated for the fabrication of solid-state devices for gas sensing applications. Albeit SnO2-based gas sensors exhibit high response to reducing gases, they suffer of poor selectivity and degradation of electrical properties at low oxygen partial pressure and high operating temperatures upon prolonged exposure to reducing gases [2]. Instead, TiO2 is more thermally stable than SnO2, but it has a lower sensitivity due to a higher density of surface states, that entails the pinning of the Fermi level [3]. SnO2 and TiO2 would easily form solid solutions because they can exhibit a rutile type structure where octahedrally coordinated Ti4+ and Sn4+ have similar ionic radii (i.e. 0.605 Å and 0.69 Å, respectively) [4,5].In an earlier investigation, the sensing properties of Sn1-x TixO2 (0.2<x<0.7) oxides prepared through sol-gel route from stoichiometric solutions of the two metal-alkoxides have been explored [6]. Sn1-xTixO2 solid solution showed better sensing performances than SnO2 and TiO2 under different target gases, with the Sn0.7Ti0.3O2 solid solution overperforming with respect to the other investigated compounds [6].Despite the Sn1-x Ti x O2 good sensing performances, a further improvement on the sensing aptitude of these materials has been attempted by means of a Nb doping. The incorporation of Nb5+ within the Sn0.7Ti0.3O2 lattice would increase the conductivity of the material, as niobium acts as donor dopant in n-type semiconductors and it can inhibit grain growth [7]. Scope and Methods The aim of this work was to study the sensing properties and the structural features of solid solutions based on Sn, Ti and Nb oxides. According to what reported in a previous investigation [6], different sample of (Sn,Ti,Nb)xO2 were synthesized keeping constant the Sn/Ti stoichiometric ratio (70/30) at different Nb doping of 2, 3.5 and 5% of the total metal amount, and hereafter labelled as STN 2, STN 3.5 and STN 5. As synthetized powders were heated at 650 and 850 °C for 2h (STN Nb% 650, STN Nb% 850) to investigate the possible influence of the temperature on grain size, Nb percolation and sensing properties. Observations at SEM microscopy revealed that the morphology of the samples consists of rounded nanoparticles. Samples heated at 650 °C are composed by grains with diameters from 10 to 30 nm, while those heated at 850 °C showed a more uniform grain size distribution (30-40 nm). Along with a small fraction of TiO2 nanocrystalline phase (about 2.5% on average), X-ray powder diffraction analyses confirm that the (Sn,Ti,Nb)xO2 with rutile-type structure is the main phase in all the investigated samples. On the base of the refined unit-cell parameters a 17% substitution of Ti4+ (i.r. 0.605Å) and Nb5+ (i.r.=0.64Å) for the bigger Sn4+ (i.r.=0.69Å) was estimated.The sensing performance of (Sn,Ti,Nb)xO2 sensors were investigated toward various gases (H2, CO, ethanol, NO2, CH4 and acetaldehyde) at their optimal working temperature of 450 °C. As shown in figure 1a, it was found that the STN 2 650 sample exhibit a response to hydrogen 6 to 8 times higher than STN 2 850 and SnO2 650, respectively. Moreover, STN 2 650 displays a better stability in wet conditions (Fig 1b). Despite the increase of relative humidity (RH%) affects the response to hydrogen, the dynamic response to H2 of the sample heated at 650 °C remains still high (Fig. 1c).Thanks to its outstanding characteristics, (Sn,Ti,Nb)xO2 solid solution is a promising candidate for hydrogen detection. The sensing properties towards other gases will be considered.

Solid-Solution Photocatalysts: New Insights Via Percolation Theory

Solid-solution semiconductors in many metal-oxynitride and metal-chalcogenide systems have been demonstrated to efficiently drive water oxidation and/or reduction under visible-light irradiation as suspended powders or thin films, respectively. This occurs despite the high level of inherent atomic-level disorder that would normally be expected to decrease charge mobility and increase charge recombination in these systems. Within the mixed-metal oxides, current results will be presented on the syntheses, structures and photoelectrochemical properties of the solid solutions Cu5(Ta1-x Nb x )11O30 and (Ba1-x Sn x )(Zr1-yTi y )O3 with band gaps that span the visible light energies from ~1.9 to 3.1 eV. Their band gaps, band edge energies and photocatalytic activities for the production of molecular hydrogen and molecular oxygen are found to be a sensitive function of their Ta-to-Nb or Zr-to-Ti and Ba-to-Sn molar ratios, as shown in the Figure for the (Ba1-x Sn x )(Zr1-yTi y )O3 solid-solution semiconductor. Notably, electronic structure calculations reveal that the highest photocatalytic activities should occur at the percolation thresholds of the mixed transition-metal frameworks, wherein extended diffusion pathways for the minority carriers start to form across the surfaces. In the semiconductors that will be described, the extended diffusion pathways constitute the lowest energies of the conduction bands and/or highest energies of the valence bands, and thus revealing an underlying driving force for achieving efficient charge separation in solid-solution systems. Figure 1

Screening Transition Metals (Mn, Fe, Co, and Cu) Promoted Ni-Based CO2 Methanation Bimetal Catalysts with Advanced Low-Temperature Activities

The Ni monometallic catalyst usually exhibits poor CO₂ methanation activity, although its low cost is beneficial for conducting large-scale application in industries. Herein, the transition metal (Mn, Fe, Co, and Cu)-doped Ni-based bimetallic catalysts loaded on mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were prepared to address this challenge in CO₂ methanation. We found that the Co-doped catalysts exhibited much higher activity than the corresponding counterparts. Therefore, the relationship between the Co/Ni ratio and activity was further investigated to acquire the optimum ratio. The obtained catalysts were characterized by various measurements. The results demonstrated that doping the second transition metals could promote Ni dispersion and strengthen metal–support interaction. Resultantly, serious agglomeration of the metallic active sites was successfully inhibited. Besides, we also carried out the in situ diffuse reflectance infrared spectroscopy and online temperature-programmed surface reaction of CO₂ methanation to study the possible reaction intermediates and pathways over the Ni–Co bimetallic catalysts. A dynamic study was also conducted to further study the effect of the doped transition metals on the apparent activation energies. Besides, the present research also revealed that the Ni–Co synergistic effect significantly improved the low-temperature activity by regulating the reaction intermediates. As a result, the Ni–Co bimetallic catalysts supported by mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were considered as a series of promising and efficient low-temperature CO₂ methanation catalysts.

UO2–Y2O3 ceramic nuclear fuel: SPS fabrication, physico-chemical investigation and neutron absorption evaluation

The paper studies spark plasma sintering of UO2-based ceramics nuclear fuel obtained from a mixture of pristine urania with 2 and 8 wt% of Y2O3 (integral fuel burnable absorber) produced by liquid-phase ultrasonic homogenizing. Densification dynamics of UO2-Y2O3 system is investigated for the first time in the temperature range up to 1250 °C under spark plasma sintering (SPS) conditions followed by a comparative analysis with UO2-Gd2O3 and UO2-Eu2O3 analogs. Earlier unknown data on formation of (U,Y)O2 solid solutions, isostructural to UO2, under SPS conditions is presented. Structural changes manifested in stable pore and defect occurrence within the ceramics bulk are shown to depend on Y2O3 amount proving the occurrence of the Kirkendall effect, which is commonly known phenomenon in the field of traditional methods of fuel manufacturing. Microhardness (HV), compressive strength (σcs) and density (ρ) are found to degrade in the presence of Y2O3, however their values remain within acceptable limits. For the first time, neutron-activation analysis is implemented as a laboratory means to assess neutron absorption efficiency of the SPS fuels containing various IFBA additives (Gd2O3, Eu2O3, Y2O3). These novel results contribute to the fundamental knowledge on the range of possible applications available owing to nonconventional SPS technology, thus extending the methods palette of fuel fabrication as well as providing new characterization approaches to probe important fuel properties for nuclear power engineering field.