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Recently, high-entropy alloys (HEAs) and HEA-type compounds have been extensively studied in the fields of material science and engineering. In this article, we report on the synthesis of a layered system

To expand the process window for the rapid solid-state crystal growth (RSSCG) method, through which large unitary single crystals of a (K0.5Na0.5)NbO3 (KNN) system can be synthesized in a short time, we varied the dominant fabrication parameters, the B-site excess ratio and the Bi2O3 content, over a range wider than that utilized in previous studies. Unitary single crystals were obtained at the B-site excess ratios of 0.75%–1.75%; particularly, 1.00% and 1.25% were found to be suitable for the synthesis. Electron spin resonance analysis showed that the concentration of oxygen vacancies increased with increasing B-site excess ratios and decreased with increasing amount of added Bi2O3 in the calcined powder. The optimization of the critical driving force for crystal growth by controlling oxygen vacancy concentration was found to be key to growing the large unitary single crystals appropriately by the RSSCG method.

Spinel-type CoV2O4 compound shows cubic-to-tetragonal phase transition with a very small distortion (1 – c/a

We investigated the effects of 0.5 mol% to 6.0 mol% CuO addition on crystal growth by the rapid solid-state crystal growth method to synthesize large unitary rectangular (K,Na)NbO3 (KNN) single crystals several square centimeters within 24 h. X-ray photoelectron spectroscopy and X-ray powder diffraction measurements revealed that CuO and Cu2O segregated in the region near the coarsened single crystal/polycrystal boundary. A positive correlation between crystal growth and the addition of CuO up to 1.5 mol% was observed; however, for CuO amounts larger than 1.5 mol%, this correlation became negative. To investigate these phenomena, a high-precision synchrotron powder diffraction measurement was performed. Significant precipitation of the CuO phase was detected in the calcined powders with a CuO addition larger than 1.5 mol%. The effects of this precipitation on the growth mechanism for coarsening the single crystals were discussed.

Recently, high-entropy alloys (HEAs) and HEA-type compounds have been extensively studied in the fields of material science and engineering. In this article, we report on the synthesis of a layered system MBi2Te4 where the M site possesses low-, middle-, and high-entropy states. The samples with M = Pb, Ag1/3Pb1/3Bi1/3, and Ag1/5In1/5Sn1/5Pb1/5Bi1/5 were newly synthesized and the crystal structure was examined by synchrotron X-ray diffraction and Rietveld refinement. We found that the M-Te2 distance was systematically compressed with decreasing lattice constants, where the configurational entropy of mixing at the M site is also systematically increased. The details of structural refinements and the electrical transport property are presented.

The effect of dynamic high-pressure loading on the decomposition reaction and negative thermal expansion of Ag2O was investigated by X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The XRD pattern of the sample shocked at 6.4 GPa indicated that the sample was composed of cubic phase Ag2O and metallic Ag. These XRD patterns indicated that the shock-induced decomposition reaction of Ag2O occurred when the sample was shock-loaded at 6.4 GPa and above. The DSC curves of the shocked Ag2O revealed that an additional exothermic reaction occurred at around 478 K in addition to an endothermic reaction at around 700 K, which corresponds to the decomposition of Ag2O. The exothermic reaction at around 478 K was probably caused by the release of shock-induced residual energy. Synchrotron XRD performed from 300 to 130 K clarified the suppression of negative thermal expansion in the shocked Ag2O.

A new crystalline lithium-ion conducting material, Li4SnS4 with an ortho-composition, was prepared by a mechanochemical technique and subsequent heat treatment. Synchrotron X-ray powder diffraction was used to analyze the crystal structure, revealing a space group of P63/ mmc and cell parameters of a = 4.01254(4) A and c = 6.39076(8) A. Analysis of a heat-treated hexagonal Li4SnS4 sample revealed that both lithium and tin occupied either of two adjacent tetrahedral sites, resulting in fractional occupation of the tetrahedral site (Li, 0.375; Sn, 0.125). The heat-treated hexagonal Li4SnS4 had an ionic conductivity of 1.1 × 10-4 S cm-1 at room temperature and a conduction activation energy of 32 kJ mol-1. Moreover, the heat-treated Li4SnS4 exhibited a higher chemical stability in air than the Li3PS4 glass-ceramic.

The desertification of coastal regions is a worldwide problem. It is believed that one of the potential influences is a reduction in the concentration of dissolved iron in seawater. On the other hand, there is a high demand for the use of steelmaking slag generated from iron works. Steelmaking slag concrete, hereafter referred to as SSC, is made from the byproducts of steelmaking, such as steelmaking and ground granulated blast-furnace slags. It has been shown that although SSC releases iron, the dissolved iron is oxidized and precipitates promptly. In the present research, porous-type SSC (POSSC) using hot-metal pretreatment slag (HPS) as an aggregate was manufactured, with the purpose of increasing the amount of iron released from HPS. In addition, the influence of incorporating humus into the paste on the concentration of dissolved iron in artificial seawater and the compressive strength of POSSC was investigated. Two commercially available leaf mulches were used as the humus. The effects of the void ratio and the water-to-binder ratio of the paste were also examined. As a result, it was confirmed that the larger the measured void ratio of the POSSC, the higher the concentration of total iron released by the POSSC. It was also demonstrated that, although a humus fraction of 2% of the volume of the HPS caused an approximately 2 N/mm2 reduction in the compressive strength, the humus clearly stabilized the long-term presence of dissolved iron in the artificial seawater.

Green-emitting Tb3+-doped pollucite (Cs1-3xTbx)AlSi2O6 (x = 0.01–0.13) phosphors were synthesized by the high-temperature solid-state reaction method. Structural characterization of the prepared (Cs1-3xTbx)AlSi2O6 phosphors was performed using powder X-ray diffraction and X-ray photoelectron spectroscopy. The excitation and emission spectra showed green emission at ~543 nm because of the 5D4→7F5 transition under excitation at 238 nm. The optimum doping concentration of the Tb3+ ions was x = 0.07, and the quantum efficiency was 83.6%. The temperature dependence of emission spectra for x = 0.07 revealed that 92.7% and 78.4% of the initial value of the emission intensity at 300 K are retained at 400 K and 500 K, respectively. These results show that the green-emitting phosphors synthesized herein have good performance and potential applications in ultraviolet-C excited white light-emitting diodes.

The high-pressure (HP) crystal polymorph of a fluorinated ionic liquid (fIL) was determined using X-ray diffraction and Raman spectroscopy. The irreversible crystal polymorph of 1-butyl-3-methylimidazolium perfluorobutanesulfonate ([C4mim][PFBS]) was observed upon compression and decompression using X-ray diffraction. Conformational variance/invariance of [C4mim]+ and [PFBS]− in the Raman spectra corresponded to the HP crystal polymorph. By the degrees of freedom of the conformations and their conformational flexibilities, the conformational variance was switched at the specific pressure for a volume contraction under HP, at which point the crystal system changed. The HP crystal polymorph was entirely different from the low-temperature crystal polymorph.

Alloying magnetic ions into halide double perovskites brings new opportunities for spintronics., Spintronics holds great potential for next-generation high-speed and low–power consumption information technology. Recently, lead halide perovskites (LHPs), which have gained great success in optoelectronics, also show interesting magnetic properties. However, the spin-related properties in LHPs originate from the spin-orbit coupling of Pb, limiting further development of these materials in spintronics. Here, we demonstrate a new generation of halide perovskites, by alloying magnetic elements into optoelectronic double perovskites, which provide rich chemical and structural diversities to host different magnetic elements. In our iron-alloyed double perovskite, Cs2Ag(Bi:Fe)Br6, Fe3+ replaces Bi3+ and forms FeBr6 clusters that homogenously distribute throughout the double perovskite crystals. We observe a strong temperature-dependent magnetic response at temperatures below 30 K, which is tentatively attributed to a weak ferromagnetic or antiferromagnetic response from localized regions. We anticipate that this work will stimulate future efforts in exploring this simple yet efficient approach to develop new spintronic materials based on lead-free double perovskites.

A series of Eu2+ substituted pollucite [(Cs1-xEu1-2x)AlSi2O6 (CASO:xEu) (x = 0.001–0.08)] phosphors were synthesized by a high-temperature solid-state reaction method in a reducing atmosphere and characterized by X-ray diffraction, photoluminescence (PL), and PL excitation (PLE) measurements. Under excitation at 275 nm, CASO:xEu phosphors exhibit an emission band that shifts from the bright blue region with color coordinates of (0.159, 0.247) to the bright blue-green region with color coordinates of (0.225, 0.421) with increasing x. Such tunable luminescence color was attributed to the crystal field splitting effect of Eu2+ ions because the substitution of Eu2+ created vacancies at Cs sites, and fluctuations occurred at the positions occupied by the Eu2+ ions. Studies on the temperature dependence of luminescence for x = 0.01, 0.03 0.05, and 0.07 in CASO:xEu reveal that 92.5%, 85.3%, 74.9%, and 79.8% of the initial value of the luminescence intensity at 300 K are retained at 400 K, respectively. Tuning the emission spectra was possible by varying the value of x while maintaining a high thermal stability.

Hidden crystal phases of fluorinated ionic liquids (fILs) at low temperature were clarified by simultaneous measurements using X-ray diffraction and differential scanning calorimetry. The fILs studied are 1-alkyl-3-methylimidazolium perfluorobutanesulfonate, [Cnmim][PFBS] (n = 4, 6, and 8). The crystal polymorphs of all [Cnmim][PFBS] appeared both upon cooling and heating. The phase varieties of fILs increased with an increase in the alkyl chain length, n. Density functional theory calculations provided the anisotropic electrostatic potential surface of the [PFBS]− anion. The complicated phase behaviors of fILs, including metastable phases, were derived from two conformations and the anisotropic electrostatic potential surface of the [PFBS]− anion.

We adjusted the B site excess ratio and the quantity of additional Bi2O3 in the KNN calcined powder in order to establish a process to fabricate, (K,Na)NbO3 (KNN)-based single crystals, with large and uniform configurations and relatively stable low porosity, using the seed-free solid-state crystal growth method. When the activity of abnormal grain growth during sample heating was controlled appropriately by adding 0.5 wt% Bi2O3 into the calcined powder with a B site excess ratio of 1%, extraordinarily large unitary rectangular single crystals were grown successfully. The individual crystals started to grow from the nucleus around the center of the green compacts formed by the calcined powder. Then they expanded until they became larger than 15 × 15 mm2 by heating at 1060 °C for 15 h. The relative density of the fabricated single crystals was higher than 99%.

Phase behaviors and magnetic properties of magnetic ionic liquids (mILs) were investigated at low temperature. The mILs were [C4mim][FeCl4], [C4mim][FeCl3Br], [C4mim][FeCl2Br2], [C4mim][FeClBr3], and [C4mim] [FeBr4], where [C4mim]+ is 1-butyl-3-methylimidazolium. The formation of symmetric and asymmetric anions was identified using Raman spectroscopy. In addition, [C4mim][FeCl4], [C4mim][FeCl3Br], and [C4mim][FeCl2Br2] indicated a paramagnetic behavior of magnetic susceptibility, which obeyed the Curie-Weiss law. In [FeClBr3]−-, and [FeBr4]−-based mILs, crystallization was induced at a low temperature upon cooling. Moreover, nonparamagnetic magnetic susceptibility was observed in [C4mim][FeClBr3], and [C4mim][FeBr4].

A new crystalline lithium-ion conducting material, Li

In frustrated spinel oxide $\mathrm{Co}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$, the knowledge of orbital, lattice, and spin structures has been fragmentary thus far. To investigate the structural and magnetic phase transitions in $\mathrm{Co}{\mathrm{V}}_{2}{\mathrm{O}}_{4}$, we performed high-resolution neutron powder diffraction, single crystal synchrotron radiation diffraction, and magnetization and specific heat measurements for high-quality samples. Extremely small crystal distortion from cubic to tetragonal phase ($1\ensuremath{-}c/al0.06%$) was observed using the high-resolution neutron diffraction measurement below ${T}^{*}\ensuremath{\sim}95\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, where a cusp was observed in the temperature dependence of magnetization. The single crystal diffraction experiment revealed that the structural phase transition accompanied by a change in the space group from $I{4}_{1}/amd$ to $I{4}_{1}/a$ occurred at ${T}_{2}=59\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, where the phase transition was observed in the specific heat measurement. Crystal and magnetic structure analysis was carried out with the neutron data, and the results suggest that the magnetic phase transition from collinear to noncollinear magnetic ordering occurs at ${T}^{*}$ and the antiferro-orbital ordering occurs below ${T}_{2}$. We discuss the observed small crystal distortion and orbital characteristics in the light of the boundary between localization and delocalization.

We synthesize herein millimeter-sized single crystals of the molecule-based chiral antiferromagnet, [NH4][Mn(HCOO)3]. The crystal is optically transparent, and has a hexagonal crystal structure tha...

We have investigated magnetic properties and phase transitions in polycrystalline and single crystal samples of the spinel compound CoV2O4 by magnetization, specific heat, and x-ray diffraction measurements. In addition to the ferrimagnetic transition, another phase transition is clearly observed at T 2 = 47 K in the specific heat measurement which has not been observed in single crystals to date. The magnetization and specific heat measurements for the polycrystalline samples of the Co1+x V2−x O4 system showed that the phase transition at T 2 is suppressed as x increases, however, it remains for x ≤ 0.15. From the result, the behavior of magnetization and specific heat in our single crystal is found to be consistent with that in the polycrystalline sample for Co1.1V1.9O4. This suggests that the fundamental physical properties of the Co1+x V2−x O4 system are determined by the concentration x and independent with whether the sample is polycrystalline or single crystal. These results reveal that the phase transition at T 2 is intrinsic in CoV2O4 and exists even in the single crystal with less excess Co. The detailed magnetic properties of the single crystal showing the transition at T 2 have also been investigated.