Solid-state Metathesis Reaction Research Articles

Simple to Quadruple Perovskite Transformation by Coordination Switching upon Solid-State Ion Exchange of NaNbO3.

Topotactic ion exchange is ubiquitous in the preparation of many metastable solids with layered structures. In recent times, the scope of chimie-douce ion exchange has been extended to quasi-2D and -3D structures including nanocrystals. The low-temperature solid-state exchange is yet another unique synthetic tool to access preconceived structures for the rational design of solids. Although rational synthesis using inorganic synthons is rare, few examples exist among inorganic solids with layered structures. Herein, we extend the scope further by transforming a simple perovskite (ABO3) into a high-pressure quadruple (AA'3B4O12) perovskite. The transformation is achieved at moderate temperatures and ambient pressure via a solid-state metathesis reaction, wherein the transition metal adopts a new A-cation coordination upon exchange. Such coordination switching upon ion exchange will open up possibilities for functionality-driven structural transformations and the rational design of new solids.

Mechanistically Guided Materials Chemistry: Synthesis of Ternary Nitrides, CaZrN2 and CaHfN2.

Recent computational studies have predicted many new ternary nitrides, revealing synthetic opportunities in this underexplored phase space. However, synthesizing new ternary nitrides is difficult, in part because intermediate and product phases often have high cohesive energies that inhibit diffusion. Here, we report the synthesis of two new phases, calcium zirconium nitride (CaZrN2) and calcium hafnium nitride (CaHfN2), by solid state metathesis reactions between Ca3N2 and MCl4 (M = Zr, Hf). Although the reaction nominally proceeds to the target phases in a 1:1 ratio of the precursors via Ca3N2 + MCl4 → CaMN2 + 2 CaCl2, reactions prepared this way result in Ca-poor materials (CaxM2-xN2, x < 1). A small excess of Ca3N2 (ca. 20 mol %) is needed to yield stoichiometric CaMN2, as confirmed by high-resolution synchrotron powder X-ray diffraction. In situ synchrotron X-ray diffraction studies reveal that nominally stoichiometric reactions produce Zr3+ intermediates early in the reaction pathway, and the excess Ca3N2 is needed to reoxidize Zr3+ intermediates back to the Zr4+ oxidation state of CaZrN2. Analysis of computationally derived chemical potential diagrams rationalizes this synthetic approach and its contrast from the synthesis of MgZrN2. These findings additionally highlight the utility of in situ diffraction studies and computational thermochemistry to provide mechanistic guidance for synthesis.

Synthesis of large-sized spherical Co-C alloys with soft magnetic properties though a high-pressure solid-state metathesis reaction.

In this work, we report a novel high-pressure solid-state metathesis (HSM) reaction to produce spherical bulk (diameters 2-4 mm) Co-C alloys (Co3C and Co1-xCx). At 2-5 GPa and 1300 °C, C atoms preferentially occupy the interstitial sites of the face-centered cubic (fcc) Co lattice, leading to the formation of metastable Pnma Co3C. The Co3C decomposes above 1400 °C at 2-5 GPa, C atoms infiltrate the interstitial sites of the fcc Co lattice, saturating the C content in Co, forming an fcc Co1-xCx solid solution while the C atoms in excess are found to precipitate in the form of graphite. The Vickers hardness of the Co-C alloys is approximately 6.1 GPa, representing a 19.6% increase compared to hexagonal close-packed (hcp) Co. First-principles calculations indicate that the presence of C atoms in the Pnma Co3C structure leads to a relative decrease in the magnetic moments of the two distinct Co atom occupancies. The Co-C alloys exhibited a soft magnetic behavior with saturation magnetization up to 93.71 emu g-1 and coercivity of 74.8 Oe; coercivity increased as the synthesis pressure rises.

Rapid solid-state metathesis reactions for the formation of cobalt–iron monoboride solid-solutions and investigation of their water splitting electrocatalytic activity

Rapid solid-state metathesis (SSM) reactions between four reactants form crystalline solid-solution cobalt iron monoborides. These mixed metal borides show improved HER activity that primarily correlates with higher cobalt content.

Y4O2(CN2)3Cl2, Its Relation to the Metal-Rich Y2Cl3, and the Photoluminescence of Y4O2(CN2)3Cl2:Ce

AbstractY4O2(CN2)3Cl2 and some isotypic rare earth (RE) carbodiimides RE4O2(CN2)3Cl2 (RE = Sm, Gd, Tb) were prepared by solid-state metathesis reaction between RECl3, REOCl and Li2CN2. The crystal structure of Y4O2(CN2)3Cl2 was solved and refined from single-crystal XRD data with the monocline space group C2/m. Homologous compounds with RE = Sm, Gd, Tb were assigned isotypically by means of XRD powder diffraction. The structure of Y4O2(CN2)3Cl2 is characterized by one-dimensional cluster chains which are showing a striking resemblance to the trans-edge bridging RE6-octahedra in the structures of Y2Cl3, β-Y2Cl3N, and RE2N(CN2)Cl, despite different numbers of cluster electrons. Crystals of RE4O2(CN2)3Cl2 appear as transparent rods. The presence of (NCN)2− ions is confirmed by infrared spectroscopy. Y4O2(CN2)3Cl2, doped with Ce3+ is a photoluminescent material that is showing an emission band in the orange region (λ = 550 nm) of the visible spectrum.

Phase-field modeling of solid-state metathesis reactions with the charge neutrality constraint

In this work, we present a phase-field model that captures the evolution of ionic concentrations and phase fractions during solid-state metathesis (SSM) reactions where diffusion limits the rate of transformation. The evolution of the mole fraction of each ion is obtained via governing equations that describe the reduction of a free energy, which includes an energy landscape with local minima located at compositions corresponding to stable products. We utilized two Lagrange multipliers to impose constraints of electroneutrality as well as on the sum of mole fractions, which were then eliminated to derive set of two partial differential equations that describe the dynamics of the mole fraction evolution. From these governing equations, the expressions for effective mobilities for the cations and the anions were obtained. We first study the effect of mobilities of ions on the reaction kinetics, using a simple model considering the ions with an identical absolute value of charge numbers. The simulation results show that the overall characteristic mobility, defined as the sum of the two effective ionic mobilities, provides an excellent measure of the rate at which reaction progresses and that the ratio of the effective mobilities of the anions and the cations signifies the manner by which the reaction progresses. We then generalize the model to consider ions with different charge numbers and tuned the mobility of ions based on their diffusion coefficients reported in the literature and experimental data from a thin-film experiment for the synthesis of FeS2 to demonstrate the capability of the model to predict the phase evolution during SSM reactions. In particular, the simulation predicts nonplanar phase evolution, which is recently observed in thin-film reactions for the synthesis of FeS2 via transmission electron microscopy. The approach can serve as a basis for models for phase transformations in other multiphase ionic mixtures, such as in all-solid-state batteries and in ionic liquids.

Synthetic Engineering in Na2MSn2(NCN)6 (M = Mn, Fe, Co, and Ni) Based on Electronic Structure Theory.

Quaternary transition metal cyanamides Na2MSn2(NCN)6 with M = Mn, Fe, Co, and Ni were prepared via solid-state metathesis reactions between Na2Sn(NCN)3 and binary transition metal fluorides MF2 in a 2:1 molar ratio. All phases crystallize isotypically in [NiAs]-derived structures (P3̅1m) with inter- and intra-layer cation ordering over the octahedral sites. This leads to a highly asymmetric coordination of the NCN2- anion, resulting in a strong degree of cyanamide character, which is confirmed via IR measurements. Intriguingly, the optical properties of Na2MSn2(NCN)6 phases change markedly as the nature of the divalent transition metal is varied, and UV-vis measurements evidence a band gap reduction from Mn (3.43 eV) via Fe (1.90 eV) to Co (1.75 eV), which broadly mirrors the DFT+U calculated energetic interval from the Fermi level to the unoccupied 3d states. Mott-Schottky analysis then goes on to characterize Na2FeSn2(NCN)6 and Na2CoSn2(NCN)6 as n-type semiconductors with flat-band potentials of 0.46 and -0.24 eV, respectively, vs RHE. This study demonstrates the utility of transition metal substitutions, within a flexible cyanamide framework, to electronically tune this growing family of pseudo-oxides.

Synthesis of perovskite-type LaWN3 by high-pressure solid-state metathesis reaction

Perovskite-type LaWN3 was synthesized by the solid-state metathesis reaction of LaCl3, WCl6, and Li3N under a pressure of 5 ​GPa and a temperature of 1573 ​K. The amount of oxygen in the synthesized sample is smaller than that in the sample prepared by the conventional ammonolysis of La2W2O9. The x-ray diffraction pattern of resulting phase can be fitted by either the meta-stable cubic structure with a Pm3¯m space group or the ground-state rhombohedral structure with an R3c space group. The indirect bandgap of ∼1.2 ​eV and the direct band gap of ∼2.2 ​eV are consistent with those of the rhombohedral structure calculated by the density functional theory calculation with the HSE06 hybrid functional.

Magnetic properties of α-KCoPO4 compound with a chiral polar crystal structure

We have obtained polycrystalline samples of a metastable α variant of KCoPO4 by low temperature (350–400 °C) solid state metathesis reaction of potassium oxalate and ammonium cobalt orthophosphate. The material crystallizes in a polar chiral structure (sg. P63, no. 173). Measurements of magnetic properties reveal antiferromagnetic interactions and no ordering observed down to T = 1.9 K, well below the Weiss temperature |Θcw| = 13.9 K.

Thin-Film Paradigm to Probe Interfacial Diffusion during Solid-State Metathesis Reactions

Thin-Film Paradigm to Probe Interfacial Diffusion during Solid-State Metathesis Reactions

Carbodiimide Bridged Network Structure of [RE6O(NCN)6] Clusters in the Structure of RE8O(CN2)10Br2, RE = La, Ce, Pr, Nd

New rare earth (RE) carbodiimides having the formula RE8O(CN2)10Br2 were synthesized by solid-state metathesis reactions. Structure determinations and refinements, based on single-crystal X-ray diffraction data, are performed with the space group P͞3c1. Homologous compounds with RE = La, Ce, Pr, and Nd are assigned isotypically. The refined crystal structure appears most unusual for rare earth carbodiimide compounds. The structure is characterized by the formally neutral [RE6O(NCN)8] fragment that is tightly interconnected by carbodiimide ions into a network structure, and contains additional RE3+ ions in the structure. Crystals of the compounds show characteristic colors of their corresponding RE3+ ions and behave stable in air. The presence of (CN2)2− ions was confirmed by infrared spectroscopy. Ce8O(CN2)10Br2 is a photoluminescent material that is showing a broad and efficient emission band in the yellow region of the visible spectrum.

Rapid and Energetic Solid-State Metathesis Reactions for Iron, Cobalt, and Nickel Boride Formation and Their Investigation as Bifunctional Water Splitting Electrocatalysts

Metal borides have long-standing uses due to their desirable chemical and physical properties such as high melting points, hardness, electrical conductivity, and chemical stability. Typical metal boride preparations utilize high-energy and/or slow thermal heating processes. This report details a facile, solvent-free single-step synthesis of several crystalline metal monoborides containing earth-abundant transition metals. Rapid and exothermic self-propagating solid-state metathesis (SSM) reactions between metal halides and MgB2 form crystalline FeB, CoB, and NiB in seconds without sustained external heating and with high isolated product yields (∼80%). The metal borides are formed using a well-studied MgB2 precursor and compared to reactions using separate Mg and B reactants, which also produce self-propagating reactions and form crystalline metal borides. These SSM reactions are sufficiently exothermic to theoretically raise reaction temperatures to the boiling point of the MgCl2 byproduct (1412 °C). The chemically robust monoborides were examined for their ability to perform electrocatalytic water oxidation and reduction. Crystalline CoB and NiB embedded on carbon wax electrodes exhibit moderate and stable bifunctional electrocatalytic water splitting activity, while FeB only shows appreciable hydrogen evolution activity. Analysis of catalyst particles after extended electrocatalytic experiments shows that the bulk crystalline metal borides remain intact during electrochemical water-splitting reactions though surface oxygen species may impact electrocatalytic activity.

A green and economical route to the precursor for the synthesis of single crystal LiNi0.5Co0.2Mn0.3O2

Single crystal LiNi1-x-yCoxMnyO2(NCM) cathode materials are typically synthesized using spherical polycrystalline hydroxides which are often prepared via coprecipitation reactions. However, the spherical morphology of polycrystalline hydroxides is not essential for the precursor in the synthesis of single crystal NCM, and also the coprecipitation process is not environmentally friendly and cost-effective enough. Herein a new process based on room-temperature solid-state metathesis reactions is developed to prepare the precursor for the synthesis of single crystal LiNi0.5Co0.2Mn0.3O2(NCM523). The whole process is free of any undesirable chemicals, and the resulting nanosize precursor can facilitate the synthesis of micron-level single crystal NCM523 at relatively lower sintering temperatures with less lithium excess. Moreover, the obtained single crystal NCM523 can exhibit comparable reversible capacities as compared with that synthesized from the coprecipitated spherical polycrystalline hydroxides. This work demonstrates a green and economical route to the precursor for the synthesis of single crystal NCM.

Sodium-Stuffed Open-Framework Quaternary Chalcogenide Built with (Cu2Ga6S18)16- Ribbons Cross-Linked by Unusual Linear Cu(I) Pillars.

A quaternary compound, Na15Cu3Ga6S18, the first member in the A-Cu-Ga-S (A = alkali metal) series, has been synthesized from a solid-state metathesis reaction between Na6Ga2S6 and CuCl as well as from a combination of Na2S, Ga, Cu, and S. The compound crystallizes in a monoclinic crystal system, space group C2/c, and represents a unique open-framework structure with channels filled with eight crystallographically distinct Na ions. The anionic framework is built up of infinite chains of corner-shared GaS4 tetrahedra fused together by an edge-shared dimer of CuS4 tetrahedra forming one-dimensional ribbons of (Cu2Ga6S18)16-, which are cross-linked by linearly coordinated S-Cu-S linkages resulting in a three-dimensional network with tunnels filled with Na atoms. Optical band gap measurements show that the compound has a direct band gap of 3.00 eV that is in good agreement with the theoretical band gap derived from density functional theory calculations. Band structure calculations further indicate that the states near the Fermi level are dominated by tetrahedral Cu+(d) and S(p) states resulting from the antibonding interactions, while s-d hybridization is prevalent in linear Cu+ coordination. Ionic conductivity measurements show that the compound has a room-temperature Na ion conductivity of 2.72 × 10-5 mS/cm with an activation energy of 0.68 eV, which corroborates well the nudged elastic band calculations.

Advanced Inorganic Nitride Nanomaterials for Renewable Energy: A Mini Review of Synthesis Methods.

Inorganic nitride nanomaterials have attracted widespread attention for applications in renewable energy due to novel electrochemical activities and high chemical stabilities. For different renewable energy applications, there are many possibilities and uncertainties about the optimal nitride phases and nanostructures, which further promotes the exploration of controllable preparation of nitride nanomaterials. Moreover, unlike conventional nitrides with bulk or ceramic structures, the synthesis of nitride nanomaterials needs more accurate control to guarantee the target nanostructure along with the phase purity, which make the whole synthesis still a challenge to achieve. In this mini review, we mainly summarize the synthesis methods for inorganic nitride nanomaterials, including chemistry vapor deposition, self-propagation high-temperature synthesis, solid state metathesis reactions, solvothermal synthesis, etc. From the perspective of nanostructure, several novel nitrides, with nanostructures like nanoporous, two-dimensional, defects, ternary structures, and quantum dots, are showing unique properties and getting extensive attentions, recently. Prospects of future research in design and synthesis of functional inorganic nitrides are also discussed.

Lowering Ternary Oxide Synthesis Temperatures by Solid-State Cometathesis Reactions

Low-temperature synthesis routes are necessary for selectively synthesizing many metastable solid-state materials. Here, we identify a cooperative effect that starting materials have in lowering temperatures in solid-state metathesis reactions by studying the formation of yttrium manganese oxide. Previous studies have shown that YMnO3 can be synthesized by ternary metathesis with an alkali halide being produced as a secondary product. In this contribution, we show that by using alkaline earth metals instead of alkali metals, the polymorph selectivity of the reaction is changed, as orthorhombic YMnO3 forms at lower temperatures than the hexagonal polymorph. Reactions were studied using ex post facto synchrotron X-ray diffraction. These experiments reveal that reactions using alkaline earth manganese oxides as a starting material require high temperatures to progress. Reaction temperatures can be lowered from 700 to 550 °C while maintaining phase selectivity by reacting both MgMn2O4 and CaMn2O4 with YOCl in a cooperative “cometathesis” reaction. The nascent halide salts appear to improve the reaction kinetics. Since the onset temperature for YMnO3 formation falls 50 °C below the MgCl2–CaCl2 liquidus, the enhanced reactivity is consistent with the surface melting of a nasscent salt byproduct at the interfaces. Cometathesis routes have similar phase selectivity and temperature reduction in reactions that form TbMnO3, ErMnO3, and DyMnO3. Cometathesis lowers reaction temperatures while preserving the reaction selectivity of the end members, making it a valuable approach for synthesizing metastable targets.

Pressure-induced disordering of site occupation in iron–nickel nitrides

Controlled disordering of substitutional and interstitial site occupation at high pressure can lead to important changes in the structural and physical properties of iron–nickel nitrides. Despite important progress that has been achieved, structural characterization of ternary Fe–Ni–N compounds remains an open problem owing to the considerable technical challenges faced by current synthetic and structural approaches for fabrication of bulk ternary nitrides. Here, iron–nickel nitride samples are synthesized as spherical-like bulk materials through a novel high-pressure solid-state metathesis reaction. By employing a wide array of techniques, namely, neutron powder diffraction, Rietveld refinement methods combined with synchrotron radiation angle-dispersive x-ray diffraction, scanning electron microscopy/energy dispersive x-ray spectroscopy, and transmission electron microscopy, we demonstrate that high-temperature and high-pressure confinement conditions favor substitutional and interstitial site disordering in ternary iron–nickel nitrides. In addition, the effects of interstitial nitrogen atoms and disorderly substituted nickel atoms on the elastic properties of the materials are discussed.

The effect of interstitial-site nitrogen on structural, elastic, and magnetic properties of face-center cubic Co

Cobalt plays a crucial role in the systematic understanding of magnetic phenomena originating from 3d transition metals. Particularly, recent studies of Co systems doped with nitrogen (Co–N) have attracted a lot of attention for applications in spintronics and high-density magnetic data-storage devices. In this work, in order to understand the effect of interstitial incorporation of N atoms into a face-center cubic (fcc) Co lattice, we have studied the structure, elastic, and magnetic properties of spherical-like bulk CoNx (x = 0.06–0.07) samples. These samples were synthesized through a high-pressure solid-state metathesis reaction. We demonstrate that the use of a certain concentration of interstitial N atoms tends to stabilize the lattice of fcc Co at ambient conditions. Such a stabilizing effect is found to originate from the covalent bond between Co atoms and N atoms. High-pressure synchrotron x-ray diffraction indicates that the incorporation of N atoms into fcc Co has little effect on the elastic property up to 27.2 GPa with a bulk modulus (B0) of 200 GPa; the latter is found to be comparable to that of fcc and hcp Co. CoNx samples exhibited ferromagnetic behavior with saturation magnetization up to 153.55 emu/g and coercivity of 16.25 Oe. The introduction of small amounts of nitrogen in the cobalt matrix was found to induce a significant decrease in the coercive force parameter.

Dinitrogen as a Universal Electron Acceptor in Solid-State Chemistry: An Example of Uncommon Metallic Compounds Na3(N2)4 and NaN2.

With the exception of lithium, alkali metals do not react with elemental nitrogen either at ambient conditions or at elevated temperatures, requiring the search for alternative synthetic routes to their nitrogen-containing compounds. Here using a controlled decomposition of sodium azide (NaN3) at high pressure conditions, we synthesize two novel compounds, Na3(N2)4 and NaN2, both containing dinitrogen anions. NaN2 synthesized at 4 GPa might be the common intermediate in high-pressure solid-state metathesis reactions, where NaN3 is used as a source of nitrogen, while Na3(N2)4 opens a new class of compounds, where [N2] units accommodate a noninteger formal charge of 0.75-. This finding can dramatically extend the expected compositions in other group 1 and 2 metal-nitrogen systems. Electronic structure calculations show the metallic character for both compounds.

Photothermal Transduction Efficiencies of Plasmonic Group 4 Metal Nitride Nanocrystals.

The photothermal transduction efficiencies of group 4 metal nitrides, TiN, ZrN, and HfN, at λ = 850 nm are reported, and the performance of these materials is compared to an Au nanorod benchmark. Transition metal nitride nanocrystals with an average diameter of ∼15 nm were prepared using a solid-state metathesis reaction. HfN exhibited the highest photothermal transduction efficiency of 65%, followed by ZrN (58%) and TiN (49%), which were all higher than those of the commercially purchased Au nanorods (43%). Computational studies performed using a finite element method showed HfN and Au to have the lowest and highest scattering cross section, respectively, which could be a contributing factor to the efficiency trends observed. Furthermore, the changes in temperature as a function of illumination intensity and solution concentration, as well as the cycling stability of the metal nitride solutions, were studied in detail.