Circumventing Diffusion in Kinetically Controlled Solid-State Metathesis Reactions

• DOI: 10.1021/jacs.6b06367
• Publication Date: 2016-08-04T14:53:23Z
• Authors: Andrew J. Martino...; Joshua A. Kurzman; James R. Neilson
• Keywords: Exothermic reaction; Metastability; Salt metathesis reaction

Solid-state diffusion is often the primary limitation in synthesis of crystalline inorganic materials and prevents potential discovery isolation new that may not be most stable with respect to reaction conditions. Synthetic approaches circumvent solid-state reactions are rare allow formation metastable products. To this end, we present an situ study metathesis MCl2 + Na2S2 → MS2 2 NaCl (M = Fe, Co, Ni) using synchrotron powder X-ray diffraction differential scanning calorimetry. Depending on preparation method reaction, either combining reactants air-free environment or grinding homogeneously air before annealing, barrier product formation, therefore pathway, can altered. In reactions, appears limited, a number intermediate phases observed product. However, allows form directly without annealing displaces corresponding metal sulfide ions into amorphous matrix, as confirmed by pair distribution function analysis. Heating mixture yields direct nucleation phase avoids all binary intermediates. Grinding also dissipates large amount lattice energy via NaCl, crystallization much less exothermic process. This approach has range binary, ternary, higher-ordered compounds synthesized bulk, while avoiding many intermediates otherwise diffusion-limited reaction.