Host Ions Research Articles

Removal of Radioactive Co(II) and Sr(II) using (Co0.5Zn0.5)Fe2O4 Nanoparticles Co-doped with Barium and Antimony

Radioactive pollution poses significant environmental and health risks, including increased cancer rates, genetic mutations, and ecosystem damage, making the removal of radioactive ions from water crucial. Spinel ferrite nanoparticles are promising adsorbents for this purpose owing to their magnetic and adsorption properties. Herein, the novel synthesis of (Co0.5−xZn0.5−xBaxSbx)Fe2O4 nanoparticles (0 ≤ x ≤ 0.1) is reported as an effective solution for adsorbing radioactive Co(II) and Sr(II) ions. Co-doping with Ba and Sb enhances the structural stability, magnetic behavior, and adsorption efficiency of these nanoparticles. X-ray diffraction analysis confirmed sample purity with minimal hematite phase, while Fourier transform infrared spectroscopy verified the spinel structure. Transmission electron microscopy analysis revealed spherical morphology and indicated that increasing x from 0.00 to 0.10 reduced crystallite and grain sizes of nanoparticles from 11.28 to 6.49 nm and 24.47 to 10.88 nm, respectively. Energy-dispersive X-ray spectroscopy confirmed pure elemental compositions and the successful substitution of host ions with dopant ions in the nanoparticles, while X-ray photoelectron spectroscopy analysis provided insights into the chemical oxidation states. Vibrating sample magnetometer results indicated soft ferromagnetic behavior. In adsorption experiments, we examined contact time (0–180 min), pH (2–10), adsorbent dosage (0.04–0.10 g), initial ion concentration (10–250 mg.L−1), and temperature (293–313 K) to determine their effects on adsorption efficiency and optimize conditions for maximum contaminant removal. Nanoparticles with x = 0.06 exhibited the highest ion-removal efficiencies, achieving 88.3% for Co(II) and 96.3% for Sr(II) after contact time of 180 min, with maximum efficiencies observed at pH 8 for Co(II) and pH 6 for Sr(II). Co(II) adsorption followed the Freundlich isotherm, while Sr(II) adsorption adhered to the Temkin model. Kinetics for both ions conformed to the pseudo-second-order model, demonstrating the potential of Ba and Sb co-doped ferrite nanoparticles for efficient radioactive-water purification.

(Invited) Operando Nanoimaging of Phase Transformations in Energy Storage Materials

We applied operando Bragg Coherent Diffractive Imaging (BCDI) to study the discontinuous phase transformation in LixNi0.5Mn1.5O4 embedded in a fully operational battery. During Li-intercalation, we observed nucleation and growth of the Li-rich phase in a 500 nm particle embedded in the multicomponent positive electrode. The data captures the evolution from a curved coherent to planar semi-coherent interface, driven by dislocation dynamics. These dislocations travel with the interface and are expelled upon the completion of the phase transformation, resulting in a crystal devoid of defects. We hypothesize that these defects move via glissile motion without diffusion of host ions. Our data indicate the absence of significant kinetic limitations affecting the transformation kinetics, even under rapid discharge within 2 hours. This study underscores the capability of BCDI as a powerful tool for operando analysis of nanoscale phase transformations, offering guidance for the design and optimization of electrochemical materials.

Groups IV, V and VI metal oxide-containing hydrotalcite catalysts: state of the art on their catalytic applications

The present contribution is a review paper that summarizes the structure, properties and catalytic applications of hydrotalcite based materials when they are modified by the incorporation of oxide metals from groups 4, 5 and 6. The unique properties of hydrotalcites, with a double layer structure able to host ions in the interlayer space and its basicity, together with the properties of transitions metal oxides from groups 4, 5 and 6, leads to materials highly promising as catalysts. The incorporation can form dispersed species of those oxides on the hydrotalcite-like structure, which acts as support, or by the incorporation of those elements into the hydrotalcite structure. The structure and properties of these materials have been reviewed and analyzed, in order to give a detailed description of the main factors that affect the catalytic properties of these interesting materials.

Theoretical Study of Magnetization and Electrical Conductivity of Ion‐Doped KBiFe2O5 Nanoparticles

The electrical conductivity σ and magnetization M of (KBFO) nanoparticles (NPs) are systematically examined using a microscopic model and Green's function theory. KBFO is characterized by a narrow bandgap and relatively weak electrical conductivity σ, which presents a problem in carrier transportation and collection. Therefore, ways to enhance σ are found. The first is reducing the NP size. The second one is doping at the Fe and Bi sites with different ions which cause a compressive strain, that is, their ionic radius is smaller than that of the host ion. It is shown that doping with Al at the Fe site as well as with Ru or La ions at the Bi site leads to enhancing the electrical conductivity σ. The magnetization M increases with increasing concentration of all dopants.

Structural, Optical, and Morphological Study of Manganese Substituted Cobalt Ferrite and Its Effect on the Magnetic and Dielectric Properties of PVA Composites

Nanopowders of Mn-substituted CoFe2O4 were prepared in different proportions using the sol-gel auto-combustion method and were structurally and morphologically studied. In another step, composites based on polyvinyl alcohol (PVA) with Mn-substituted CoFe2O4 fillers were prepared, and the effect of the Mn-substituted CoFe2O4 on the optical, magnetic, and dielectric properties was studied. X-ray analysis revealed the formation of polycrystalline Mn-substituted CoFe2O4. The results showed a decrease in the lattice constant with Mn2+ substituted and incorporated into the crystal structure of CoFe2O4. The Fourier confirmed the spinel structure of the Mn-substituted CoFe2O4 transform infrared spectrum where absorption bands appeared at 569–561 and 446–407 cm-1, which are attributed to tetrahedral and octahedral groups. The magnetic properties were affected when Mn ions were substituted with CoFe2O4, as shown by the results of VSM. It was observed that the saturation magnetization, remnant magnetization, and coercivity decreased with increasing Mn content. The dielectric constant and loss tangent of PVA/MnxCo1−xFe2O4 were also studied. The difference in the diameters of the substituted and host ions causes the dielectric constant to increase following the substitution of Mn ions.

Aqueous Rechargeable Manganese/Iodine Battery

AbstractCarbon neutralization has promoted the identification of new types of energy storage devices. Aqueous iodine batteries (AIBs) with reversible iodine redox activity are considered a viable candidate for stationary energy storage units and thus have recently drawn extensive research interest. Herein, we introduce an aqueous manganese iodine battery (AMIB), utilizing sodium iodide (NaI) as a redox‐active additive in the Mn(ClO4)2 (NMC) electrolyte, activated carbon (AC) as a redox host and Mn ions as the charge carrier. Taking advantage of enhanced kinetics facilitated by I2/2I− redox activity, our suggested AMIBs can be electrochemically charged/discharged with only a 6 % loss in capacity after 2,000 cycles at a low current density of 0.3 A g−1 in an AC||AC coin cell configuration. Moreover, the AC||Zn−Mn hybrid full‐cell configuration is also established with AC and a Zn−Mn anode involving the NMC electrolyte, which retains a high energy of 185 Wh kg−1 at a specific power of 2,600 W kg−1. Overall, the AMIBs in this study preferred I2/I− conversion chemistry, yielding stable cycle stability, rate performance, and low capacity loss per cycle when compared to Manganese Ion Batteries (MIBs) which are based on Mn2+ intercalation chemistry.

Physiochemical interaction between osmotic stress and a bacterial exometabolite promotes plant disease

Various microbes isolated from healthy plants are detrimental under laboratory conditions, indicating the existence of molecular mechanisms preventing disease in nature. Here, we demonstrated that application of sodium chloride (NaCl) in natural and gnotobiotic soil systems is sufficient to induce plant disease caused by an otherwise non-pathogenic root-derived Pseudomonas brassicacearum isolate (R401). Disease caused by combinatorial treatment of NaCl and R401 triggered extensive, root-specific transcriptional reprogramming that did not involve down-regulation of host innate immune genes, nor dampening of ROS-mediated immunity. Instead, we identified and structurally characterized the R401 lipopeptide brassicapeptin A as necessary and sufficient to promote disease on salt-treated plants. Brassicapeptin A production is salt-inducible, promotes root colonization and transitions R401 from being beneficial to being detrimental on salt-treated plants by disturbing host ion homeostasis, thereby bolstering susceptibility to osmolytes. We conclude that the interaction between a global change stressor and a single exometabolite from a member of the root microbiome promotes plant disease in complex soil systems.

Bandgap Energy of Ion‐Doped LaMnO3 Nanoparticles

Based on the s‐d model combined with Green's function technique, the magnetization and the bandgap energy of ion‐doped nanoparticles at La sites are calculated. Due to the change of the valency of Mn ions, from to , as well as the difference between the ionic radii of the doping and host ions, the exchange interaction is modified which allows a tuning of the magnetization and the bandgap energy. For nanoparticles, the bandgap is decreased by Ag and Ba doping, whereas it is increased by K and Sr doping. Macroscopic quantities such as the magnetization and the bandgap energy are directly related to microscopic parameters of the model. The simulations are qualitatively in good agreement with the experimental data.

Electrochemical Failure Mechanism of δ-MnO2 in Zinc Ion Batteries Induced by Irreversible Layered to Spinel Phase Transition.

Phase transitions of Mn-based cathode materials associated with the charge and discharge process play a crucial role on the rate capability and cycle life of zinc ion batteries. Herein, a microscopic electrochemical failure mechanism of Zn-MnO2 batteries during the phase transitions from δ-MnO2 to λ-ZnMn2O4 is presented via systematic first-principle investigation. The initial insertion of Zn2+ intensifies the rearrangement of Mn. This is completed by the electrostatic repulsion and co-migration between guest and host ions, leading to the formation of λ-ZnMn2O4. The Mn relocation barrier for the λ-ZnMn2O4 formation path with 1.09eV is significantly lower than the δ-MnO2 re-formation path with 2.14eV, indicating the irreversibility of the layered-to-spinel transition. Together with the phase transition, the rearrangement of Mn elevates the Zn2+ migration barrier from 0.31 to 2.28eV, resulting in poor rate performance. With the increase of charge-discharge cycles, irreversible and inactive λ-ZnMn2O4 products accumulate on the electrode, causing continuous capacity decay of the Zn-MnO2 battery.

Doping Effects on the Multiferroic Properties of KNbO3 Nanoparticles

The magnetization, polarization, and band-gap energy in pure and ion-doped KNbO3 (KNO) bulk and nanoparticles (NPs) are investigated theoretically using a microscopic model and Green’s function theory. It is shown that KNO NPs are multiferroic. The size dependence of M and P is studied. The magnetization M increases with decreasing NP size, whereas the polarization P decreases slightly. The properties of KNO can be tuned by ion doping, for example, through the substitution of transition metal ions at the Nb site or Na ions at the K site. By ion doping, depending on the relation between the doping and host ion radii, different strains appear. They lead to changes in the exchange interaction constants, which are inversely proportional to the lattice parameters. So, we studied the macroscopic properties on a microscopic level. By doping with transition metal ions (Co, Mn, Cr) at the Nb site, M increases, whereas P decreases. Doped KNO NPs exhibit the same behavior as doped bulk KNO, but the values of the magnetization and polarization in KNO NPs are somewhat enhanced or reduced due to the size effects compared to the doped bulk KNO. In order to increase P, we substituted the K ions with Na ions. The polarization increases with increasing magnetic field, which is evidence of the multiferroic behavior of doped KNO bulk and NPs. The behavior of the band-gap energy Eg also depends on the dopants. Eg decreases with increasing Co, Mn, and Cr ion doping, whereas it increases with Zn doping. The results are compared with existing experimental data, showing good qualitative agreement.

X-ray excited optical luminescence from lanthanide ions in double phosphate and double silicate crystalline hosts

X-ray Excited Optical Luminescence (XEOL) from rare earth doped whitlockite phosphates and silicate garnets [Ca9La(PO4)7 and Ca9Lu(PO4)7, doped with 1 mol% Ce3+; Ca3Sc2Si3O12, doped with 0.5 mol% Pr3+, 1 mol% Eu3+ and 1 mol% Tb3+], was obtained upon X-ray excitation with a tunable synchrotron light source. Excitation at photon energies across the M5,4-edge of the dopants reveals additional information not normally obtainable with conventional UV/visible or an X-ray line source (Al Kα). It is found that despite the low concentration, photoluminescence yields excited with photon energy at the M5,4-edge of the rare-earth dopant can positively and negatively affect the overall energy transfer to the optical center. The implication of these observations is discussed. The application of XEOL in the investigation of X-ray scintillators is illustrated.

Novel high-sensitivity optical thermometry based on fluorescence intensity ratio of <inline-formula><tex-math id="Z-20240425115725">\begin{document}${\text{VO}}_4^{3 - } $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_Z-20240425115725.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_Z-20240425115725.png"/></alternatives></inline-formula> to Pr<sup>3+</sup>

It is noteworthy that since 2010, the number of published and cited scientific papers on optical thermometry has increased exponentially. Optical thermometry technology is about to make a significant process in sensing, therapy, diagnosis, and imaging. The current research mainly focuses on optical thermometry that is developing towards high-sensitivity thermometry. In this work, a new thermometry strategy is proposed based on the different temperature-dependent behaviors between the host ions and the doped ions. Firstly, YVO<sub>4</sub>:<i>x</i>Pr<sup>3+</sup>(<i>x</i> = 0%–1.5%) phosphors are successfully synthesized by the solid-state method. Then, the structure and luminescence properties of the samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and fluorescence spectrophotometer. The XRD results show that Pr<sup>3+</sup> ions are successfully incorporated into the YVO<sub>4</sub> host, and the sample has a tetragonal phase crystal structure with space group <i>I</i>41/<i>amd</i>. The SEM results show that the samples are rectangular-shaped micron particles with smooth surfaces, and the average grain size is about 2.1 μm. Under the excitation of 320 nm, the sample mainly exhibits broadband blue emission around 440 nm and red emission at 606 nm, which are attributed to the charge transfer transition of <inline-formula><tex-math id="M2">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M2.png"/></alternatives></inline-formula> and the <sup>1</sup>D<sub>2</sub>→<sup>3</sup>H<sub>4</sub> transition of Pr<sup>3+</sup>, respectively. The relationship between the luminescence of the sample and the concentration of Pr<sup>3+</sup> is studied. It is found that the optimal doping concentration of Pr<sup>3+</sup> is 0.5%, and a higher doping concentration will cause concentration to be quenched. The reason for quenching concentration is the electric dipole-quadrupole interaction. The luminescence peak position of the temperature-dependent spectrum of YVO<sub>4</sub>:0.5%Pr<sup>3+</sup> is consistent with that at room temperature. As the temperature increases, the total luminescence intensity gradually decreases, which is caused by thermal quenching, and the mechanism of thermal quenching is analyzed. Since the temperature-dependent behaviors of luminescence of <inline-formula><tex-math id="M3">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M3.png"/></alternatives></inline-formula> and Pr<sup>3+</sup> are significantly different from each other, a new fluorescence intensity ratio thermometry strategy is realized. Temperatures range is 303–353 K, and the maximum absolute sensitivity and relative sensitivity are 0.651 K<sup>–1</sup> and 3.112×10<sup>–2</sup> K<sup>–1</sup> at 353 K, respectively, much higher than the traditional thermally coupled level thermometry strategy. In addition, there is no obvious overlap between the emission peaks of <inline-formula><tex-math id="M4">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M4.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M4.png"/></alternatives></inline-formula> and Pr<sup>3+</sup>, which provides a good discrimination capability for signal detection. The above results show that this work provides a promising path for designing self-reference optical thermometry materials with excellent temperature sensitivity and signal discrimination.

Harnessing point-defect induced local symmetry breaking in a tetragonal-HfO2 system through sterically mismatched ion doping

Defect-engineering is a frequent approach to modify the material's properties.

Multiferroic Properties of Co, Ru, and La Ion Doped KBiFe2O5.

The magnetic, electric, dielectric, and optical (band gap) properties of ion doped multiferroic KBiFe2O5 (KBFO) have been systematically investigated utilizing a microscopic model and the Green's function theory. Doping with Co at the Fe site and Ru at the Bi site induces changes in magnetization, coercive field, and band gap energy. Specifically, an increase in magnetization is observed, while the coercive field and band gap energy decrease. This behavior is attributed to the distinct ionic radii of the doped and host ions, leading to alterations in the exchange interaction constants. The temperature dependence of the polarization P reveals a distinctive kink at the Neel temperature TN, which shifts to higher temperatures with an increase in the applied magnetic field h. Furthermore, doping with Ru and La leads to an increase in polarization. The temperature dependence of the dielectric constant exhibits two peaks at the Neel temperature TN and the Curie temperature TC. Notably, these peaks diminish with increasing frequency. Additionally, the dielectric constant demonstrates a decrease with the rise in the applied magnetic field h. This study sheds light on the intricate interplay between ion doping, structural modifications, and multifunctional properties in KBFO, offering valuable insights into the underlying mechanisms governing its behavior across various physical domains.

Revealing the mechanism of manganese doping in sulphoaluminate cement clinker

The production of cement clinker from solid waste generated by industrial development is a valid way to reduce the exploitation of natural resources and protect the environment. This paper reports the doping behavior of manganese (Mn) ions in sulphoaluminate cement (SAC) clinker. Results from energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and density functional theory (DFT) simulations indicate that Mn ions enter C4AF by replacing Fe ions, and rarely incorporate into the other two minerals, C4A3S‾ and C2S. Further analysis of the partial density of states (PDOS) and electron density difference (EDD) indicates that the Mn doping mechanism can be ascribed to the comparable electronic contributions of the host and guest ions. These insights into the doping behavior of Mn ions will provide meaningful information to guide the utilization of Mn-containing solid waste as an alternative raw material for the synthesis of SAC clinker.

Interfacial molecular structure of phosphazene-based polymer electrolyte at the air-aqueous interface using sum frequency generation vibrational spectroscopy

The change induced in the physicochemical properties of polymer while hosting ions provides a platform for studying its potential applications in electrochemical devices, water treatment plants, and materials engineering science. The ability to host ions is limited in very few polymers, which lack a detailed molecular-level understanding for showcasing the polymer-ion linkage behavior at the interfacial region. In the present manuscript, we have employed sum frequency generation (SFG) vibrational spectroscopy to investigate the interfacial structure of a new class phosphazene-based methoxyethoxyethoxyphosphazene (MEEP) polymer in the presence of lithium chloride salt at the air-aqueous interface. The interfacial aspects of the molecular system collected through SFG spectral signatures reveal enhanced water ordering and relative hydrogen bonding strength at the air-aqueous interface. The careful observation of the study finds a synchronous contribution of van der Waals and electrostatic forces in facilitating changes in the interfacial water structure that are susceptible to MEEP concentration in the presence of ions. The observation indicates that dilute MEEP concentrations support the role of electrostatic interaction, leading to an ordered water structure in proximity to diffused ions at the interfacial region. Conversely, higher MEEP concentrations promote the dominance of van der Waals interactions at the air-aqueous interface. Our study highlights the establishment of polymer electrolyte (PE) characteristics mediated by intermolecular interactions, as observed through the spectral signatures witnessed at the air-aqueous interface. The investigation illustrates the polymer-ion linkage adsorption effects at the interfacial region, which explains the macroscopic changes observed from the cyclic voltammetry studies. The fundamental findings from our studies can be helpful in the design and fine-tuning of better PE systems that can offer improved hydrophobic membranes and interface stability for use in electrochemical-based power sources.

Identification of structural and optical properties and adsorption performance of (Cd0.4Ni0.4Mn0.2)Fe2-xRuxO4 nanoparticles for the removal of Congo red dye

In the field of industrial wastewater treatment, the application of highly efficient methods such as adsorption is crucial for effectively eliminating dangerous pollutants before effluent discharge. Ferrite nanoparticles (NPs) have emerged as promising candidates for the efficient and sustainable removal of dyes from wastewater. Therefore, the synthesis, characterization, and application of (Cd0.4Ni0.4Mn0.2)Fe2-xRuxO4 (0 ≤ x ≤ 0.04) NPs as adsorbents for the removal of Congo Red (CR) dye, is reported in this study. The X-ray powder diffraction (XRD) analysis has confirmed the purity of the samples with a very small amount of hematite phase. The prepared NPs have pseudo-spherical morphology and average particle size in the range of 12–17 nm. Furthermore, the elemental compositions, estimated from the energy dispersive x-ray (EDX) measurements, indicate the homogenous distribution of elements and the substitution of the Fe3+ host ions by the Ru3+ dopant. As the Ru content increases from 0.00 to 0.04, SBET increases from 52.39 to 78.34 m2/g, respectively. Furthermore, the pore diameter, ranging between 12.71 and 18.38 nm, reveals the mesoporous nature of the prepared samples. The direct and indirect bandgap energy, calculated from UV–vis spectroscopy analysis, is in the range of 3.049–3.232 eV and 1.894–2.642 eV, respectively. The adsorption performance of the prepared NPs for the removal of CR dye solution was investigated by varying the contact time, adsorbent amount, pH, and reaction temperature. The adsorption process follows a second-order kinetic model and the NPs with x = 0.015 revealed the highest adsorption rate with a rate constant k2 = 2.7 × 10−3 g.mg−1.min−1. The optimum experimental conditions, achieved in the presence of 80 mg of (Cd0.4Ni0.4Mn0.2)Fe1.985Ru0.015O4 NPs at 308 K and in the acidic medium at pH = 3.45, result in the removal of 87.5 % of CR dye after 60 min. After applying several non-linear adsorption isotherm models, mainly Langmuir, Freundlich, and Temkin isotherms, the experimental data were well-fitted with the Temkin isotherm model. The strong interactive force between CR and (Cd0.4Ni0.4Mn0.2)Fe1.985Ru0.015O4 nanoparticles is revealed from the high value of bT knowing that bT = 182.91 J.mol−1.

Host-sensitized colour-tunable emission and Judd-ofelt analysis for Dy3+-doped ZnGa2O4 phosphor through exciton-mediated energy transfer

Single-phase Dy3+-doped zinc gallate (ZnGa2O4) phosphors were synthesized using a conventional solid-state fabrication technique. The structural properties of the host phosphor were determined through X-ray powder diffraction (XRPD) and Rietveld refinement, revealing a cubic spinal structure with a space group of Fd3m. The reflectance properties of the host and doped samples were measured using UV–Vis spectroscopy. The obtained data were used to estimate the bandgap of all the synthesized samples, ranging from 4.18 to 3.69 eV, confirming the formation of a wide bandgap semiconductor. Morphological, compositional, and surface mapping analyses were conducted using a field emission scanning electron microscope, energy dispersive electron spectroscopy, and time-of-flight secondary ion mass spectroscopy. X-ray photoelectron spectroscopy was employed to confirm the oxidation state of the constituent elements and for an in-depth study of the crystal structure. Photoluminescence excitation and emission spectra were recorded to analyze the luminescent properties of the synthesized phosphors. It was confirmed that when using an excitation wavelength of 247 nm, all samples exhibited broad host emission with decreasing intensity. In contrast, Dy3+ emission displayed an increasing trend, confirming host sensitization in this phosphor. To analyze the radiative properties of the activator ion, theoretical analysis using the Judd-Ofelt theory was carried out. The results revealed an overlapping of orbitals between the O2− ion and Dy3+, indicating its higher-order covalent nature and the increased symmetric nature of the activator ion in the present host. This characteristic allowed for the generation of near-white light emissions. A concentration of 7 mol% of Dy3+ was observed to match well with achromatic white (0.32, 0.33) on the color chromaticity diagram. The luminous properties of this material suggest that it is a desirable candidate for use in LEDs and AC electroluminescent systems.

First-Principles Dynamics Investigation of Germanium as an Anode Material in Multivalent-Ion Batteries

Germanium, a promising electrode material for high-capacity lithium ion batteries (LIBs) anodes, attracted much attention because of its large capacity and remarkably fast charge/discharge kinetics. Multivalent-ion batteries are of interest as potential alternatives to LIBs because they have a higher energy density and are less prone to safety hazards. In this study, we probed the potential of amorphous Ge anodes for use in multivalent-ion batteries. Although alloying Al and Zn in Ge anodes is thermodynamically unstable, Mg and Ca alloys with Ge form stable compounds, Mg2.3Ge and Ca2.4Ge that exhibit higher capacities than those obtained by alloying Li, Na, or K with Ge, corresponding to 1697 and 1771 mA·h·g–1, respectively. Despite having a slightly lower capacity than Ca–Ge, Mg–Ge shows an approximately 150% smaller volume expansion ratio (231% vs. 389%) and three orders of magnitude higher ion diffusivity (3.0 × 10−8 vs. 1.1 × 10−11 cm2 s−1) than Ca–Ge. Furthermore, ion diffusion in Mg–Ge occurs at a rate comparable to that of monovalent ions, such as Li+, Na+, and K+. The outstanding performance of the Mg–Ge system may originate from the coordination number of the Ge host atoms and the smaller atomic size of Mg. Therefore, Ge anodes could be applied in multivalent-ion batteries using Mg2+ as the carrier ion because its properties can compete with or surpass monovalent ions. Here, we report that the maximum capacity, volume expansion ratio, and ion diffusivities of the alloying electrode materials can be understood using atomic-scale structural properties, such as the host–host and host–ion coordination numbers, as valuable indicators.

Unraveling the Correlation between Structure and Lithium Ionic Migration of Metal Halide Solid-State Electrolytes via Neutron Powder Diffraction

Metal halide solid-state electrolytes (SSEs) (Li-M-X system, typically Li3MX6 and Li2MX4; M is metal or rare-earth element, X is halogen) exhibit significant potential in all solid-state batteries (ASSB) due to wide stability windows (0.36–6.71 V vs. Li/Li+), excellent compatibility with cathodes, and a water-mediated facile synthesis route for large-scale fabrication. Understanding the dynamics of Li+ transportation and the influence of the host lattice is the prerequisite for developing advanced Metal halide SSEs. Neutron powder diffraction (NPD), as the most cutting-edge technology, could essentially reflect the nuclear density map to determine the whole crystal structure. Through NPD, the Li+ distribution and occupation are clearly revealed for transport pathway analysis, and the influence of the host ion lattice on Li+ migration could be discussed. In this review, we stress NPD utilization in metal halide SSEs systems in terms of defect chemistry, phase transition, cation/anion disorder effects, dual halogen, lattice dynamics/polarizability, and in situ analysis of phase evolution. The irreplaceable role of NPD technology in designing metal halide SSEs with enhanced properties is stressed, and a perspective on future developments of NPD in metal halide SSEs is also presented.