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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Synthesis and characterisation of In-doped MnWO{sub 4}-type solid-solutions: Mn{sub 1−3x}In{sub 2x}□{sub x}WO{sub 4} (x=0–0.11)

Substitution of In{sup 3+} for Mn{sup 2+} in MnWO{sub 4}, which is one of the most studied multiferroics, was conducted systematically by solid-state reactions at 1050 °C to obtain a series of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} solid solutions (x=0–0.11; the box indicates vacancy). The successful In-doping could be proven by electron microprobe, and statically disordered structures of this solid solution series were elucidated by Rietveld analyses with X-Ray powder diffraction (XPD) data. Its average structure maintains the space group P2/c at least up to the replacement of 33 at% Mn. The tendency of their unit cells proportionally enlarging with In-doping is an unexpected observation because In{sup 3+} is smaller than Mn{sup 2+}. This could not be explained alone by average atomic bonding distances and angles evaluated from XPD data analyses. Complimentarily, micro-Raman spectra of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} materials feature a hardening of Raman modes due to stronger atomic bonds in W{sub 2}O{sub 4} and WO{sub 2} units with increasing In-doping. This is considered as an inevitable consequence of broken bonding in directly neighbouring Mn–O bonds as the presence of In{sup 3+} in MnWO{sub 4} accompanies the creation of defects at Mn sites. The current study using XRD and micro-Raman suggests the enlarging local space around the bridging oxygen as the reason for the unexpected cell expansion when smaller In{sup 3+} along with defects replace Mn{sup 2+} in MnWO{sub 4}. - Graphical abstract: Despite of substitution of smaller In{sup 3+} for larger Mn{sup 2+}, the In-rich solid solution Mn{sub 0.71(2)}In{sub 0.19(1)}□{sub 0.10}WO{sub 4} undergoes a volume expansion of 0.4% with respect to MnWO{sub 4}. This could be explained by a local space expansion of 0.13% around bridging oxygen at O2 sites, as illustrated by dashed lines for clarity. - Highlights: • Investigation of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} solid solutions (x=0–0.11). • An unexpected lattice expansion by In-doping. • Strong change in local environment around bridging oxygens. • Enhancement of atomic bonds in W{sub 2}O{sub 4} and WO{sub 2} units with increasing In-doping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1) full range solid solution: Structure, optical properties, and magnetism

Graphical abstract: The continuous modulation on crystal structure and band gap is achieved in the Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1) full range solid solution. - Highlights: • Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1) solid solution was synthesized by a hydrothermal method. • They all present a single-phase in the wolframite structure with space group P2/c. • The continuous tenability in band gap was achieved in Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1). • CoWO{sub 4} and Zn{sub 0.5}Co{sub 0.5}WO{sub 4} are antiferromagnetic and paramagnetic, respectively. - Abstract: A novel full-range solid-solution Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1) was successfully developed via a facile one-pot hydrothermal route. The phase structure and microstructure were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra and scanning electron microscopy (SEM). The Zn{sub 1−x}Co{sub x}WO{sub 4} solid solution possesses similar wolframite crystal structure with the same space group P2/c. Diffuse reflection spectroscopy (DRS) measurements on Zn{sub 1−x}Co{sub x}WO{sub 4} (0 ≤ x ≤ 1) demonstrated that the optical band gap can be continuously tuned from 3.56 eV to 2.61 eV for direct transition and 1.87 eV for indirect transition, respectively, with increasing x from 0 to 1. Magnetic susceptibility measurements reveal that CoWO{sub 4} has an antiferromagnetic transition at T{sub N} = 42 K, whereas Zn{sub 0.5}Co{sub 0.5}WO{sub 4} exhibits paramagnetic behavior. Moreover, CoWO{sub 4} and Zn{sub 0.5}Co{sub 0.5}WO{sub 4} obey the Curie–Weiss law from 200 k down to 50 K, and their effective magnetic moments were determined.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Unique Challenges for Modeling Defect Dynamics in Concentrated Solid-Solution Alloys

Recently developed concentrated solid solution alloys (CSAs) are shown to have improved irradiation performance that strongly depends on the number of alloying elements, alloying species and their concentrations. In contrast to conventional dilute alloys, CSAs are comprised of multiple principal elements randomly situated in a simple crystalline lattice. As a result, the intrinsic disorder has a profound influence on the energy dissipation pathways and defect evolution when these CSAs are subjected to ion irradiation. Extraordinary irradiation resistance, including suppression of void formation by two orders magnitude at an elevated temperature, has been achieved with increasing compositional complexity in CSAs. Yet, the intrinsic disorder poses great challenges to theoretical modelling at the electronic and atomic level. Based on recent computer simulation results from a novel set of Ni-based face-centered cubic CSAs, we demonstrate in this review that how the disorder can be tackled in theoretical modeling and what is the impact of disorder on the defect dynamics. Finally, the unique challenges of describing the energy dissipation and defect evolution in CSAs are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

The exchange interactions and the state of manganese atoms in the solid solutions in Bi{sub 3}NbO{sub 7} of cubic and tetragonal modifications

The comparative analysis of magnetic behavior of manganese-containing solid solutions Bi{sub 3}Nb{sub 1−x}Mn{sub x}O{sub 7−δ} (x=0.01−0.10) of cubic and tetragonal modifications was performed. Based on the results of magnetic susceptibility studies paramagnetic manganese atoms in solid solutions of cubic and tetragonal modifications were found to be in the form of Mn(III), Mn(IV) monomers and exchange-coupled dimers of Mn(III)–O–Mn(III), Mn(IV)–O–Mn(IV), Mn(III)–O–Mn(IV). The exchange parameters and the distribution of monomers and dimers in solid solutions as a function of the content of paramagnetic atoms were calculated. - Graphical abstract: Structural transition of cubic to tetragonal Bi{sub 3}NbO{sub 7−δ}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is more than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Local polar structure and multiferroic properties of (1−x)Bi{sub 0.9}Dy{sub 0.1}FeO{sub 3}−xPbTiO{sub 3} solid solution

The multiferroic (1–x)[0.9BiFeO{sub 3}–0.1DyFeO{sub 3}]–xPbTiO{sub 3} (BDF–xPT) solid solution with compositions around the morphotropic phase boundary (x = 0.25, 0.28, 0.31, 0.34, and 0.37) has been synthesized in the form of ceramics. The phase symmetry, microstructure, ferroelectricity, piezoresponse, and ferromagnetic properties have been characterized by various techniques. It is found that, with increasing content of lead titanate from x = 0.25 to x = 0.37, the grain size increases and the ferroelectric property is improved. The ferroelectric performance is further enhanced by the introduction of an excess amount (2%) of TiO{sub 2} or by sintering in oxygen atmosphere, which reduces the leakage. The local polar structure is imaged by piezoresponse force microscopy. Both the out-of-plane and in-plane images reveal distinct ferroelectric domain structures, with the amplitude and the average domain size decreasing with the increase of lead titanate amount. Compared with the (1–x)BiFeO{sub 3}–xPbTiO{sub 3} binary solid solution of about the same concentration of PT, the magnetic properties are enhanced in BDF–xPT due to the presence of dysprosium, as demonstrated by the ferromagnetic hysteresis loops displayed at room temperature and at 10 K, but the remnant magnetization decreases with increasing PT content. The simultaneous presence of ferroelectricity and ferromagnetism entitles the BDF–xPT solid solution a room-temperature multiferroic material.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis of luminescent nanocrystals and solid solutions in the YNbO{sub 4}–EuNbO{sub 4} system via hydrothermal route

Highlights: • Nanocrystals: YNbO{sub 4}:Eu{sup 3+} were directly formed under hydrothermal conditions at 240 °C. • The nanocrystals (10–20 nm) were luminescent and had ellipsoidal morphology. • The complete solid solutions in the YNbO{sub 4}–EuNbO{sub 4} system were also directly formed. • The PL intensity and R/O intensity ratio changed depending on heating temperature. - Abstract: Luminescent nanocrystals having distinctive ellipsoidal morphology and the complete solid solution of monoclinic phase in the YNbO{sub 4}–EuNbO{sub 4} system were hydrothermally formed under weakly basic conditions at 180–240 °C for 5 h. The excitation spectra of the Y{sub 1−x}Eu{sub x}NbO{sub 4} nanocrystals, which consisted of the charge transfer (CT) band around 240–270 nm due to [NbO{sub 4}]{sup 3−}–Eu{sup 3+} interaction and several sharp bands corresponding to the f–f transitions of Eu{sup 3+}, e.g. the most intense absorption band at 395 nm ({sup 7}F{sub 0}→{sup 5}L{sub 6}), showed that the compounds could be excited by both ultraviolet and visible light. A dominant red emission at 610 nm and a weak orange emission at 590 nm assigned to {sup 5}D{sub 0}→{sup 7}F{sub 2} and {sup 5}D{sub 0}→{sup 7}F{sub 1} transitions of Eu{sup 3+}, respectively were observed in the as-prepared nanocrystals containing europium under excitation at 395 nm. The heat treatment at temperatures more than 1000 °C in air was effective for the improvement in the photoluminescence intensity of the as-prepared solid solutions. By the enhancement in the crystallinity and crystallite growth of the monoclinic phase through heat treatment at 1300 °C in air, the luminescence intensity of the as-prepared solid solution, Y{sub 0.75}Eu{sub 0.25}NbO{sub 4} (x = 0.25), which showed the most significant photoluminescence, became more than 5 times as strong as that before the heat treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and dielectric properties of erbium doped BiFeO{sub 3}−PbTiO{sub 3} solid solutions

Single phase Er substituted at A-site BiFeO{sub 3}−PbTiO{sub 3} solid solutions were synthesized using solid state reaction route. The calcinations at different temperature reveals that the single and pure tetragonal phase formation has been accomplished at 1000°C. The SEM micrographs did not show any distinguishable change in grain size. The dielectric studies established that the dielectric constant decreases and ferroelectric T{sub c} increases with increase in Er.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ab initio property predictions of quinary solid solutions using small binary cells

The Set of Small Ordered Structures (SSOS) approach is an ab initio technique for modelling random solid solutions in which many small structures are averaged so that their correlation functions match those of a desired composition. SSOS has been shown to be effective in reducing the cost of density functional theory calculations relative to other well-known techniques such as cluster expansions and special quasirandom structures for modelling solid solutions. Here in this work, we demonstrate that SSOS’s can be constructed using cells with only a subset of elements while still accurately modelling multi-component systems. Specifically, we show that small binary cells can effectively model two quinary high entropy alloys – NbTaTiHfZr and MoNbTaVW – accurately capturing properties such as formation energy, lattice parameters, elastic constants, and root-mean-square atomic displacements. Overall, this insight is useful for those looking to construct databases of such small structures for predicting the properties of multi-component solid solutions, as it greatly decreases the number of structures that needs to be considered.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Influence of the electron-phonon interaction on the temperature dependence of the phonon mode frequency in the II-VI compound solid solutions

We present an experimental investigation of the temperature dependence of the TO-phonon mode frequencies for the HgTe-based II-VI semiconductor solid solutions. In the case of the ternary Hg{sub 0.9}Zn{sub 0.1}Te solid solution was shown a discontinuity in the temperature dependence of the HgTe-like T{sub 0}-mode and of the ZnTe-like T{sub 1}-mode, similar to the Hg{sub 0.85}Cd{sub 0.15}Te system [Sheregii et al., Phys. Rev. Lett. 102, 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron-phonon e-p interaction which in this case is returnable—the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg{sub 0.85}Cd{sub 0.15}Te and Hg{sub 0.90}Zn{sub 0.10}Te containing Dirac point (E{sub g} ≡ Γ{sub 6} – Γ{sub 8} = 0) although one of the two constants describing the anharmonic shift of the HgTe-like mode should be positive what is abnormal too. In the case of the Hg{sub 0.80}Cd{sub 0.20}Te and Hg{sub 0.763}Zn{sub 0.237}Te solid solution, the role of the returnable e-p contribution is negligible but a positive temperature shift for the HgTe-like modes occurs. This result does not allow to explain the positive temperature shift of these modes merely by the contribution of the (e-p) interaction. Indeed, the relativistic contribution to the chemical bonds induces an abnormal temperature shift of the electron states in Hg-based semiconductors—the effect is expected since the Hg d spin-orbit split contribution to chemical bonds may lead to an abnormal temperature shift of the HgTe-like modes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Suppression of vacancy cluster growth in concentrated solid solution alloys

Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solution alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structural, magnetic, and dielectric properties of solid solutions between BiMnO{sub 3} and YMnO{sub 3}

Bi{sub 1−x}Y{sub x}MnO{sub 3} (0.1≤x≤0.9) solid solutions were prepared by the high-pressure high-temperature method at 6 GPa and 1573 K. They crystallize in the GdFeO{sub 3}-type perovskite structure with the Pnma symmetry. Crystal structures of Bi{sub 0.9}Y{sub 0.1}MnO{sub 3} and Bi{sub 0.5}Y{sub 0.5}MnO{sub 3} are studied by synchrotron X-ray powder diffraction at room temperature. Only one Néel temperature, T{sub N}, is found in samples with 0.1≤x≤0.9 in comparison with two Néel temperatures observed in YMnO{sub 3} (T{sub N}=29 and 39 K). Samples with 0.5≤x≤0.9 have almost constant T{sub N}=44 K, while T{sub N} starts to increase linearly for other compositions: T{sub N}=46 K for x=0.3, T{sub N}=58 K for x=0.2, and T{sub N}=68 K for x=0.1. Field-induced transitions from canted-antiferromagnetic states to antiferromagnetic states are detected at about 30 kOe for x=0.2 and 70 kOe for x=0.1. Dielectric constant increases below T{sub N} in samples with 0.5≤x≤1, while it decreases below T{sub N} in samples with 0.1≤x≤0.3. Our data suggest that a magnetic structure changes near x=0.4. By extrapolation, we could estimate lattice parameters (a=5.9221 Å, b=7.5738 Å, and c=5.4157 Å) and T{sub N}=79 K for a hypothetical Pnma modification of BiMnO{sub 3}. - Graphical abstract: Bi{sub 1−x}Y{sub x}MnO{sub 3} solid solutions were prepared in the whole compositional range by the high-pressure method. Magnetic and dielectric data suggest that a magnetic structure changes near x=0.4. No ferroelectric properties were found. - Highlights: • Orthorhombic Bi{sub 1−x}Y{sub x}MnO{sub 3} solid solutions are prepared by the high-pressure method. • Structural, magnetic, and dielectric properties are studied. • One Néel temperature is found in all the samples. • T{sub N}=44 K for x=0.5–0.9, 46 K for x=0.3, 58 K for x=0.2, and 68 K for x=0.1. • No ferroelectricity is observed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A high-pressure route to thermoelectrics with low thermal conductivity: The solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2} (x=0.1–0.6)

Metastable rocksalt-type phases of the solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2} (x=0.1, 0.2, 0.4, 0.5 and 0.6) were prepared by high-pressure synthesis at 2.5 GPa and 400 °C. In these structures, the coordination number of In{sup 3+} is six, in contrast to chalcopyrite ambient-pressure AgInTe{sub 2} with fourfold In{sup 3+} coordination. Transmission electron microscopy shows that real-structure phenomena and a certain degree of short-range order are present, yet not very pronounced. All three cations are statistically disordered. The high degree of disorder is probably the reason why AgIn{sub x}Sb{sub 1−x}Te{sub 2} samples with 0.4<x<0.6 exhibit very low thermal conductivities with a total κ<0.5 W/K m and a lattice contribution of κ{sub ph} ∼0.3 W/K m at room temperature. These are lower than those of other rocksalt-type tellurides at room temperature; e.g. the well-known thermoelectric AgSbTe{sub 2} (κ ∼0.6 W/K m). The highest ZT value (0.15 at 300 K) is observed for AgIn{sub 0.5}Sb{sub 0.5}Te{sub 2}, mainly due to its high Seebeck coefficient of 160 µV/K. Temperature-dependent X-ray powder patterns indicate that the solid solutions are metastable at ambient pressure. At 150 °C, the quaternary compounds decompose into chalcopyrite-type AgInTe{sub 2} and rocksalt-type AgSbTe{sub 2}. - Graphical abstract: Reaction scheme, temperature characteristics of the ZT value and a selected-area electron diffraction pattern (background) of AgIn{sub 0.5}Sb{sub 0.5}Te{sub 2}, which crystallizes in a rocksalt-type structure with statistical cation disorder. Display Omitted - Highlights: • High-pressure synthesis yields the novel solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2}. • In contrast to AgInTe{sub 2}, the compounds are inert at ambient pressure. • HRTEM shows no pronounced short-range order in the disordered NaCl-type structure. • The metastable phases exhibit very low total thermal conductivities <0.5 W/K m. • ZT values of 0.15 at room temperature were measured for AgIn{sub 0.5}Sb{sub 0.5}Te{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of atomic size mismatch and chemical complexity on the local lattice distortion of BCC solid solution alloys

Here, the effects of atomic size mismatch and chemical complexity on the local lattice distortion of solid-solution alloys VNbTa, TiVNbMo, TiVNbMoTa and TiVNbMoTaWRe with body-centered cubic (BCC) structure are quantitatively studied with time-of-flight neutron total scattering, extended X-ray absorption fine structure (EXAFS) measurements and first principles calculations. Neutron atomic pair distribution function (PDF) measurements found that the local lattice distortion in the ternary solid-solution alloy VNbTa is 1.1 %, obviously larger than that of the most complicated solid-solution alloy (0.27% for TiVNbMoTaWRe). Our results suggested that atomic size mismatch in high entropy alloys is more critical to the local lattice distortion than chemical complexity. Both EXAFS analysis and theoretical calculations indicate that there is a maximum of ~4 % difference between the bonding length of different atomic pairs in VNbTa.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Polymorphic, Porous, and Host–Guest Nanostructures Directed by Monolayer–Substrate Interactions: Epitaxial Self-Assembly Study of Cyclic Trinuclear Au(I) Complexes on HOPG at the Solution–Solid Interface

Synthesis, crystallographic characterization, and molecular self-assembly of two novel cyclotrimeric gold(I) complexes, Au 3 [3,5-(COOEt) 2 Pz] 3 (Au 3 Pz 3 ) and Au 3 [(n-Pr–O)C=N(Me)] 3 (Au 3 Cb 3 ) was studied. Single crystal X-ray crystallography data reveal that both gold(I) complexes have one-dimensional stacking patterns caused by intermolecular Au(I)···Au(I) aurophilic interactions. The Au 3 Pz 3 trimer units stack with two alternate and symmetrical Au(I)···Au(I) interactions while the Au 3 Cb 3 units have three alternating and nonsymmetrical Au(I)···Au(I) interactions. Molecular self-assembly of the gold(I) complexes on the 1-phenyloctane/highly ordered pyrolytic graphite (HOPG) (0001) solution–solid interface is studied with scanning tunneling microscopy (STM). The gold(I) cyclotrimers form epitaxial nanostructures on the HOPG surface. At a concentration of ~1 × 10 –4 M, Au 3 Pz 3 complexes exhibit a single morphology, while Au 3 Cb 3 complexes exhibit polymorphology. Two polymorphs, one nonporous and the other porous, are observed at 22.0 ± 2.0 °C for Au 3 Cb 3 complexes. A nonporous, low-surface-density (0.82 molecules/nm 2 ) Au 3 Cb 3 nanostructure forms first and then transforms into a high-density (1.43 molecules/nm2) porous nanostructure. This is the first time any porous surface nanostructure is reported for an organometallic system. The porous structure is thought to be stabilized by a combination of hydrogen bonding and monolayer–substrate interactions. These pores are utilized to incorporate pyrene into the film, rendering this the first organometallic host–guest system imaged at the solid–solution interface. In conclusion, molecular and periodic density functional theory (DFT) calculations shed light on the two-dimensional topography and polymorphic self-assembly revealed by STM; these calculations suggest significant electronic hybridization of the Au 3 trimer orbitals and HOPG. The multiple-technique approach used herein provides insights concerning molecule–substrate and molecule–molecule interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

An Optical Study of Disordering in Cadmium Mercury Telluride Solid Solutions

The disordering in cadmium mercury telluride solid solution films grown by molecular beam epitaxy on Si and GaAs substrates has been examined by optical transmission and photoluminescence investigations. The effect of a fundamental decrease in the disordering scale under thermal annealing and possible interplay of the observed phenomena with defects typical of films grown by molecular beam epitaxy are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Synthesis and Flash Sintering of (Hf1-xZrx)B2 Solid Solution Fine Powders

Fine powders of (Hf1-xZrx)B2 solid solution were synthesized by two methods. In the first one, solution-based processing of HfCl4, ZrCl4, sucrose and H3BO3 was carried out followed by heat treatment (e.g., at 1500 °C for 1 h) in Argon to achieve the carbothermal reduction (CTR) reaction to form the boride solid solution. In the second one, called boron hydride reduction (BHR) method, HfCl4, ZrCl4 and NaBH4 were directly mixed in a glove box followed by heat treatment in Argon at elevated temperatures from 700 to 1500 °C. In addition, the powders synthesized via both methods were flash sintered without sample preheating in a homemade setup. The synthesized powders as well as the flash sintered bulk ceramics were characterized using different techniques including XRD, SEM, EDS, TEM, TGA-DSC, and Vickers hardness test to reveal the inter-relationships between starting materials composition, processing conditions, and the resulting materials microstructure and physical/chemical properties.

Belisario, Jose↗