Binary Solid Solutions Research Articles

Phase Evolution in the CaZrTi2O7-Dy2Ti2O7 System: A Potential Host Phase for Minor Actinide Immobilization.

Zirconolite is considered to be a suitable wasteform material for the immobilization of Pu and other minor actinide species produced through advanced nuclear separations. Here, we present a comprehensive investigation of Dy3+ incorporation within the self-charge balancing zirconolite Ca1–xZr1–xDy2xTi2O7 solid solution, with the view to simulate trivalent minor actinide immobilization. Compositions in the substitution range 0.10 ≤ x ≤ 1.00 (Δx = 0.10) were fabricated by a conventional mixed oxide synthesis, with a two-step sintering regime at 1400 °C in air for 48 h. Three distinct coexisting phase fields were identified, with single-phase zirconolite-2M identified only for x = 0.10. A structural transformation from zirconolite-2M to zirconolite-4M occurred in the range 0.20 ≤ x ≤ 0.30, while a mixed-phase assemblage of zirconolite-4M and cubic pyrochlore was evident at Dy concentrations 0.40 ≤ x ≤ 0.50. Compositions for which x ≥ 0.60 were consistent with single-phase pyrochlore. The formation of zirconolite-4M and pyrochlore polytype phases, with increasing Dy content, was confirmed by high-resolution transmission electron microscopy, coupled with selected area electron diffraction. Analysis of the Dy L3-edge XANES region confirmed that Dy was present uniformly as Dy3+, remaining analogous to Am3+. Fitting of the EXAFS region was consistent with Dy3+ cations distributed across both Ca2+ and Zr4+ sites in both zirconolite-2M and 4M, in agreement with the targeted self-compensating substitution scheme, whereas Dy3+ was 8-fold coordinated in the pyrochlore structure. The observed phase fields were contextualized within the existing literature, demonstrating that phase transitions in CaZrTi2O7–REE3+Ti2O7 binary solid solutions are fundamentally controlled by the ratio of ionic radius of REE3+ cations.

Long-wavelength optical properties of the Ca0.33Sr0.33Ba0.33F2 solid solution single crystals

The optical characteristics of Ca0.33Sr0.33Ba0.33F2 (CSBF) single crystal of a ternary solid solution of calcium, strontium and barium fluorides were studied in order to create disordered optical media. Characteristics of the single crystals of individual fluorides CaF2, SrF2, BaF2 and binary solid solutions Ca0.6Sr0.4F2 and Ba0.67Sr0.33F2 were obtained. Broadband reflection and transmission spectra of the said crystals were recorded in the frequency range of 3–5000 cm−1, and the values of the complex refractive indexes and dielectric constants were calculated. The generalized four parameter model were used for calculation of absorption band parameters. For the CSBF crystal, a significant broadening of the band was observed in the absorption region at optical phonon modes along with an increased absorption in the region below the optical phonon frequencies, which is typical for disordered dielectric media.

Strain Engineering of Energy Storage Performance in Relaxor Ferroelectric Thin Film Capacitors

AbstractDielectric energy storage capacitors are receiving a great deal of attention owing to their high energy density and fast charging–discharging speed. The current energy storage density of dielectrics is relatively low and cannot meet the requirements of miniaturization of pulsed power equipment. Therefore, increasing the energy storage density of dielectrics has become a research hotspot. Herein, using phase‐field simulations to design polymorphic nanodomains, the strain engineering of energy storage performance of binary and ternary solid solution relaxor ferroelectric films is investigated. The results show that the energy storage performance of the ternary film is better than that of the binary film due to the polymorphic nanodomains. In addition, as the film in‐plane strain is modified from −2% to 2%, the energy density is improved by 80%, and the efficiency also increases from 52% to 77%. This work proves the remarkable energy storage performance of polymorphic films and provides a theoretical basis to optimize the energy‐storage performance of ferroelectric thin‐film capacitors by adjusting the misfit strain.

One-Dimensional Core–Shell Cd0.85Zn0.15S@Cd0.85Zn0.15MoO4 Binary Solid Solution Composite: In Situ Construction and Photocatalytic H2 Evolution Performance

One-Dimensional Core–Shell Cd_0.85Zn_0.15S@Cd_0.85Zn_0.15MoO₄ Binary Solid Solution Composite: In Situ Construction and Photocatalytic H₂ Evolution Performance

Evolution of New Phase Clusters at the Initial Stages of Binary Alloy Decomposition Described in Terms of a Modified Theory of Nucleation

The work considers the thermodynamics and the kinetics of initial decomposition stages in a supersaturated binary solid solution inthe framework of the modified nucleation theory. The specific surface energy is considered as a function of intensive state parameters of both the cluster and the matrix, which allows one to uniformly describe clusters of critical, subcritical, and supercritical size. The analysis was performed in two stages. On the first one, the optimal size dependences of the compositions of new phase clusters were determined by analyzing the macroscopic equations of growth of nuclei. On the second stage, we solved akinetic equation to describe the evolution of the size distribution function of new-phase clusters along this optimal composition line.The effect of various kinetic factors on the behavior of the distribution function and characteristics of new-phase clusters was studied. The obtained distributions demonstrate a possibility of the existence of bimodal size distributions of new-phase clusters.

A Combined Optimization Strategy for Improvement of Comprehensive Energy Storage Performance in Sodium Niobate-Based Antiferroelectric Ceramics.

Sodium niobate (NaNbO3, NN)-based lead-free antiferroelectric (AFE) ceramics are currently the focus of most attention on account of their outstanding energy storage density. Nevertheless, the high loss energy density (Wloss) by unique field-induced AFE-ferroelectric (FE) phase transition in pure NN ceramic and low breakdown electric field (Eb) largely restrict their practical application. Here, a combined optimization strategy was aimed at ameliorating energy storage characteristics of NN-based ceramics. First, the introduction of BiFeO3-SrTiO3 binary solid solution in pure NN ceramics destroys the long-range polar ordering and reduce the tolerance factor (t), thus reducing the polarization hysteresis, stabilizing the AFE phase and enhancing the energy storage efficiency. Then, the two-step sintering method was used to improve the compactness of ceramics and reduce the grain size. Finally, the VPP method was used to reduce the porosity, and thin the ceramic disk to a thickness of ∼100 μm. The high compactness and small thickness could effectively enhance the maximum breakdown electric field of ceramics. Ultimately, the optimum energy storage characteristics were obtained by the improvement of a combined optimization strategy, namely, an exceptional recoverable energy storage density (Wrec = 5.29 J/cm3) and efficiency (η = 82.1%) at a very high breakdown electric field (Eb = 380 kV/cm). This combined optimization strategy establishes a universal approach to ameliorate the energy storage characteristics of NN-based AFE ceramics for energy storage.

Machine-Learning Prediction of Vegard's Law Factor and Volume Size Factor for Binary Substitutional Metallic Solid Solutions

Machine-Learning Prediction of Vegard's Law Factor and Volume Size Factor for Binary Substitutional Metallic Solid Solutions

Influence of SFT Content on Physical, Mechanical and Dielectric Properties of BNKT-SFT Binary Ceramic System

In this research, the binary solid solution Bi0.5(Na0.84K0.16)0.5TiO3 and Sr(Fe0.5Ta0.5)O3 in the system of (1-x)BNKT-xSFT was synthesized by solid-state reaction technique. The mixed powder and ceramics of (1-x)BNKT-xSFT where x=0.00, 0.01, 0.02, 0.03 and 0.04 were calcined at 900 °C for 2 h and sintered at 1125 °C for 2 h. The sintered ceramic samples were investigated phase formation, densification, mechanical properties, and dielectric constant at room temperature. The XRD analysis of all condition samples shows a pure phase perovskite structure. The maximum of bulk density, HV, HK microhardness, the elastic modulus, fracture toughness, and dielectric constant were found at x= 0.04 condition which the value is 5.877 g/cm3, 6.21 GPa, 5.39 GPa, 181.12 GPa, 0.19 MPa·m1/2 and 1,404, respectively. A small among SFT content shows an improvement of densification, mechanical properties, and dielectric constant in (1-x)BNKT-xSFT ceramics. The relations of these results were discussed and compared to the previously reported.

Effect of co-addition of WC and MoSi2 on the microstructure of ZrB2–SiC–Si composites

In this paper, ZrB2–SiC–Si-based ceramic composites with WC and MoSi2 additives were fabricated using SPS method and their densification behavior was investigated by phase and microstructural studies. During the SPS process and according to the prevailing conditions, WC and MoSi2 additives reacted with the surface oxide impurities of the main raw materials. As a result of these reactions and the decomposition of some raw materials, a series of oxide liquid phases formed, which were often Si-based, and due to their good fluidity, undissolved and free elements such as Zr, Mo and W moved to open porosities and grain boundaries. According to the established thermodynamic conditions, binary solid solutions and new phases such as MoB, ZrC and WB formed. The synthesis of such phases boosted the densification of the composites due to the fact that they formed in porosities or voids between the main grains. The results showed that the sample doped with 2.5 vol% WC and 2.5 vol% MoSi2 had the highest relative density (about 99%). Meanwhile, microstructural studies showed that homogeneous and dense parts can be achieved by SPS technology.

Softening of antiferroelectric order in a novel PbZrO3-based solid solution for energy storage

PbZrO3-based antiferroelectric (AFE) materials have received growing attention for their attractive energy storage performance. However, a major drawback of PZ is its high critical electric field (Ecr) which makes it difficult to switch the antiparallel dipoles therein so as to be useful. Therefore, softening of AFE order in PbZrO3 is thought to be a promising approach for its practical applications. In this work, a new binary AFE solid solution of (1-x)PbZrO3-xPb(Mg1/2Mo1/2)O3 (PZ-PMM), with x = 0.00–0.10, was successfully synthesized in form of ceramics via the solid-state reaction method. The effect of chemical modification by introducing Pb(Mg1/2Mo1/2)O3 on the crystal structure, phase transition behavior and electrical properties of the PbZrO3 ceramics are investigated systemically. It is found that a perovskite phase with orthorhombic Pbam symmetry is preserved at room temperature for all the compositions studied, and a broadened ferroelectric intermediate phase exists between the paraelectric (PE) and the antiferroelectric phases of the PZ-PMM solid solution. At 160 °C, typical double hysteresis loop can be displayed for all the compositions. Most importantly, the maximum electric field-induced polarization is significantly increased, whereas the critical field is decreased with increasing PMM content, suggesting a remarkable softening effect of the antiferroelectric order in PZ due to some degree of dipole frustration. This work could bring about the development of a new series of PZ-based solid solutions for energy storage applications in the future.

Exothermic synthesis of binary solid solutions based on hafnium and zirconium carbides

The paper presents the results of an experimental study into the possibility of producing ultra-high temperature ceramics constituting solid solutions of HfC and ZrC carbides by the single-stage electro-thermal explosion (ETE) method under pressure. Adiabatic flame temperature and phase composition of the equilibrium final product were calculated based on thermodynamic data. It was shown that when the ZrC content in the final product is less than 20 wt.%, adiabatic flame temperature reaches 3800– 3900 K, and the combustion product contains hafnium and zirconium carbides. The effect of mechanical activation modes in an AGO-2 planetary centrifugal mill used for a reaction mixture containing Hf, Zr and C powders on its properties, phase composition formation and the microstructure of carbide solid solutions was studied. It was shown that high-energy mixing in hexane leads to the destruction of the crystal structure of Hf and Zr particles and the formation of amorphous composite particles. The synthesized samples of ultra-high temperature ceramics were studied by X-ray phase and microstructure analyzes. It was shown that exothermic synthesis leads to the formation of single-phase solid solutions of HfC and ZrC carbides with the average particle size of 0.2–1.5 μm. The residual porosity of the binary carbides obtained is 10–12 %. It was found that, despite the high temperature of sample heating during ETE under pressure, the particle size of the resulting solid solutions is significantly (by an order of magnitude) smaller than the particle size of similar complex carbides (20–50 μm) obtained by other methods (SPS and hot pressing). This is associated with the rapidity of the exothermic interaction of the reagents (10–50 ms) during ETE.

Radiation-resistant binary solid solutions via vacancy trapping on solute clusters

Additions of solute that trap vacancies slow down vacancy diffusion and promote point-defect recombination in alloys subjected to irradiation. Such selective alloying can thus help to minimize the detrimental consequences resulting from point defect fluxes. The current work investigates the effect of solute additions on the recombination rate using kinetic Monte Carlo simulations for a model alloy system, which was parametrized to Cu-Ag in the dilute limit, but with an increased solubility limit, ≈ 0.86 at.% at 300 K. As the solute concentration was increased above 0.1 at.%, solute clustering was observed and led to a strong increase in recombination rate. The beneficial effects of solute clustering on reducing vacancy mobility, and reducing solute drag, were analyzed by calculating relevant transport coefficients using the KineCluE code (Schuler et al., Computational Materials Science (2020) 172,109,191). Moreover, it was observed in the KMC simulations that large recombination rates resulted in a shift of steady-state distributions of solute cluster sizes to smaller clusters compared to equilibrium distributions in the solid solution. This shift is rationalized as resulting from the irreversible character of the interstitial-vacancy recombination reaction. These results suggest a novel irradiation effect on phase stability where a high recombination rate increases the solubility limit of a solute at steady state over its equilibrium value.

Investigation of iridium, ruthenium, rhodium, and palladium binary metal oxide solid solution thin films for implantable neural interfacing applications

Metal oxide solid solution thin films containing binary mixtures of iridium, ruthenium, rhodium, and palladium were combinatorially synthesized by DC reactive magnetron sputtering to investigate the compositional dependence of properties relevant to neural interfacing applications. The binary metal oxides studied included Ir(1-x)MxOy where M = Pd, Rh, and Ru. The properties of the binary metal oxides are compared to that of their single metal oxide endmembers which include palladium oxide (PdOx), ruthenium oxide (RuOx), rhodium oxide (RhOx), and iridium oxide (IrOx). The binary metal oxides exceed the electrochemical performance of their respective single metal oxide endmembers (as measured by cyclic voltammetry) at film thicknesses generally greater than 700 nm. The binary metal oxide concentrations which produce robust microstructures and exceptional electrochemical performance have been identified to be but are not limited to x ≥ 0.5 for Ir(1-x)RhxOy, x ≥ 0.34 for Ir(1-x)RuxOy, and x ≥ 0.14 for Ir(1-x)Pdx Oy. XPS analyses suggest that the electrochemical enhancements observed are at least partly due to the presence of higher oxidation states in the binary metal oxides when compared to that of the corresponding single metal oxide endmembers.

Phase evolution and relaxor to ferroelectric phase transition boosting ultrahigh electrostrains in (1−x)(Bi1/2Na1/2)TiO3-x(Bi1/2K1/2)TiO3 solid solutions

Owing to the complex composition architecture of these solid solutions, some fundamental issues of the classical (1−x)Bi1/2Na1/2TiO-xBi1/2K1/2TiO3 (BNT-xBKT) binary system, such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses, remain unresolved. In this work, we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization, but also temperature-dependent polarization versus electric field (P-E) and current versus electric field (I-E) curves. Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and electrostrain characterizations. As the temperature increased above 100 °C, the x = 0.19 composition produces ultrahigh electrostrains (> 0.5%) with high thermal stability. The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase transition and ferroelectric-to-relaxor diffuse phase transition during heating. More specifically, we revealed the relationship between phase evolution and electrostrain responses based on the characteristic temperatures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations. This work not only clarifies the phase evolution in BNT-xBKT binary solid solution, but also paves the way for future strain enhancement through doping strategies.

Binary perovskite solid solutions and trends in their phase transitions temperatures variation

Some of the known binary ABO3 perovskites with ferro- (FE) or antiferroelectric (AFE) at [Formula: see text] and different magnetic phase transitions (PT): ferro-and antiferromagnetic at [Formula: see text] and also some of their solid solutions are considered. Some correlations between their FE or AFE and/or magnetic PTs temperatures, on the one hand, and their interatomic bond [Formula: see text]–O strains, on the other hand, have been constructed. It is shown that in the plotted diagrams these temperatures change with a change in [Formula: see text] values as follows: classical FEs are followed by multiferroics, starting with BiFeO3 and ending with YVO3, followed by classical AFEs. At the same time, the temperatures [Formula: see text] and [Formula: see text] experience maxima at the corresponding points for BiFeO3, then quickly decrease, and the difference between them, [Formula: see text]-[Formula: see text], basically also decreases, slightly increasing along the way to the point EuTiO3. which made it possible to systematize these [Formula: see text] and [Formula: see text].

Static Displacements and Short-Range Order in Ni-14 at. % Ir Alloy

In this paper, we are proposing a novel method to estimate static displacements of atoms caused by size effects in fcc substitutional binary polycrystalline solid solutions. Fourier transforms of static displacements of the atoms on every considered shell were calculated using the equations that include dynamical matrix and Fourier transform of interatomic forces. Short-range order parameters on the first seven shells of Ni-14 at. % Ir alloy have been identified from X-ray diffuse scattering intensity by accounting microscopic static displacements of atoms on a particular shell. Pairwise interatomic potentials on the considered shells and critical temperature of disorder-order phase transition were calculated using values of short-range order parameters.

Pressure dependence of thermodynamic interaction parameters for binary solid solution phases: An atomistic simulation study

The effect of pressure on the interaction parameters (enthalpy of mixing) of face-centered cubic (FCC) and body-centered cubic (BCC) binary solid solution phases has been investigated using atomistic simulations at 0 K based on semi-empirical interatomic potentials (the second nearest-neighbour modified embedded-atom method: 2NN MEAM). First, it is confirmed that the 2NN MEAM interatomic potentials reproduce the pressure dependence of enthalpy and molar volume of pure elements in excellent agreement with thermodynamic modelling and experimental data. The prediction of pressure dependence is then extended to binary solid solutions. It is shown that the pressure dependence of binary interactions is clearly correlated with the sign of excess volume of corresponding solid solution phases. That is, the enthalpy of mixing shifts toward the positive direction with pressure if the excess volume shows a positive deviation from the linear average of constituent elements, while it shifts toward the negative direction in the opposite case. The results can be interpreted well by the functional form for the pressure dependence of Gibbs free energy of solution phases. An atomistic computational approach to estimate the pressure dependence of the excess volume of solution phases is also proposed.

Role of polar nanoregions in the enhancement of the recoverable energy storage density and electrostrictive coefficient in the lead free Na0.25K0.25Bi0.5TiO3

The electrostrictive materials are gaining attention for the actuating application because of their positive strain irrespective to the electric field direction and low hysteresis loss. In this work, the room temperature electrostrictive effect of lead free ferroelectrics Na0.3K0.2Bi0.5TiO3 and Na0.25K0.25Bi0.5TiO3 are studied. Due to the relaxor nature of Na0.25K0.25Bi0.5TiO3, sprout shape strain (S) and pinched polarization (P) loops are noticed as a function of electric field (E), which are beneficial for high electrostrictive coefficient and recoverable energy storage density, respectively. The reversible transformation of the polar nanoregion into the ferroelectric domain with electric field is the reason behind the sprout shape S-E loop. This composition shows the dielectric constant of ≈4000 and strain of 0.30% without any Sneg (negative value of strain). The obtained value of the electrostrictive coefficient from the S vs. P2 graph of Na0.25K0.25Bi0.5TiO3 is ≈0.022 m4/C2, which is comparable to 0.93Na0.5Bi0.5TiO3-0.07BaTiO3 composition and other Na0.5−xKxBi0.5TiO3-based binary solid solutions.

Resistive Switching Effect of Multiferroic Complex Oxide Solid Solution Thin Films

Resistive switching in multiferroics has attracted increasing attention due to the potential application for next-generation nonvolatile memory and could lead to forms of computing. However, the resistive switching mechanism in solid solution oxides is unclear. In this article, we have successfully fabricated binary 0.72BiTi0.27Fe0.46Mg0.27O3-0.28LaFeO3 (BTFM-LFO) and ternary 0.625BiTi0.27Fe0.46Mg0.27O3-0.25LaFeO3-0.125La2MgTiO6 (BTFM-LFO-LMT) thin films with precise component control by the spin coating method. The solid solution films exhibit obvious ferroelectricity and magnetism at room temperature. Both binary and ternary solid solution films show switchable polarization, weak magnetism, and reversible and repeatable resistive switching effects. Multistage resistive switching behavior was observed. Four resistive switching states were obtained in the binary film; the highest Ion/off is up to 106. The influence of the film composition on the resistive switching effect was discussed. It is considered that the oxide vacancy/valance exchange-induced defects play a dominant role in the resistive switching effect of complex oxide thin films. This work provides an alternative pathway to explore the resistive switching in multiferroic oxides by fabrication of complex solid solution films.

A simple yet general model of binary diffusion coefficients emerged from a comprehensive assessment of 18 binary systems

This study is the most comprehensive test to date aiming at defining the optimal number of fitting parameters for a reliable mathematical description of the diffusion behavior of a binary solid solution. Our systematic test of 18 diverse binary systems has yielded a surprisingly simple model with only one fitting parameter/constant which can be evaluated from experimental diffusion data. The rest of the quantities in the model are the self-diffusion and impurity (dilute) diffusion coefficients of the pure elements and the thermodynamic factor which can be computed from a CALPHAD thermodynamic assessment of the pertinent binary system. The 1-parameter Z-Z-Z model has been demonstrated to be very reliable and robust since the 18 binary systems tested in this study include very asymmetrical systems such as Co-Pd and Fe-Pd as well as Nb-Ti whose experimental diffusion coefficient data cover ~9 orders of magnitude and over a temperature range spanning ~1200°C (from ~800°C to ~2000°C). The Z-Z-Z model allows both tracer and intrinsic diffusion coefficients to be reliably computed for any composition at any temperature after the sole constant is evaluated from the interdiffusion or all experimental diffusion data. Extension of such a simple and robust model from binary to ternary and higher order systems will lead to a substantial reduction of fitting parameters and an enhancement of the reliability of future multicomponent diffusion (atomic mobility) databases for simulation of kinetic processes in materials.