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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 Ca3N2and 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 situsynchrotron X-ray diffraction studies reveal that nominally stoichiometric reactions produce Zr3+intermediates early in the reaction pathway, and the excess Ca3N2is 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 situdiffraction studies and computational thermochemistry to provide mechanistic guidance for synthesis.

Tin antimonide (SnSb) is a promising alloying anode for sodium-ion batteries due to its high theoretical capacity and relative stability. The material is popular in the battery field, but, to our knowledge, few studies have been conducted on the influence of altering Sn and Sb stoichiometry on anode capacity retention and efficiency over time. Here, Sn-Sb electrodes were synthesized with compositional control by optimizing electrodeposition parameters and stoichiometry in solution and the alloys were cycled in sodium-ion half-cells to investigate the effects of stoichiometry on both performance and electrochemical phenomena. Higher concentrations of antimony deposited into the films were found to best maintain specific capacity over 270 cycles in the tin-antimony alloys, with each cell showing a slow, gradual decrease in capacity. We identified that a 1:3 ratio of Sn:Sb retained a specific capacity of 486 mAh g−1after 270 cycles, highlighting a need to explore this material further. These results demonstrate how control over stoichiometry in Sn-Sb electrodes is a viable method for tuning performance.