Ternary nitride phase space holds great potential for new functional materials, as suggested by computational predictions of yet-to-be discovered stable phases. Here, we report a metathesis route to bulk powders of MgZrN2 and the solid solutions Mg x Zr2–x N2 (0 < x < 1). These ternary phases only result when lower temperature reactions are used, in contrast to previous work using the similar Mg-based metathesis reactions that resulted in the formation of exclusively ZrN. Thermochemical calculations illustrate why lower temperature metathesis reactions yield the incorporation of Mg, while higher temperature ceramic reactions yield exclusively ZrN. Experimental in situ X-ray diffraction of metathesis reactions during heating reveals two stages in the reaction pathway: initial consumption of the precursors to make an amorphous product (T rxn > 350 °C) followed by crystallization at higher temperatures (T rxn > 500 °C). Changing the ratio of the metathesis precursors (Mg2NCl and ZrCl4) controllably varies the composition of Mg x Zr2–x N2, which crystallizes as a cation-disordered rock salt, as evidenced by high-resolution synchrotron X-ray diffraction, electron microscopy, and bulk compositional analysis. Variation in composition leads to a gradual metal-to-insulator transition with increasing x, similar to other reports of analogous thin film specimens produced by combinatorial sputtering. Meanwhile, the optical behavior of these powders suggests nanoscale compositional inhomogeneity, as signatures of ZrN-like absorption are detectable even in Mg-rich samples. This metathesis approach appears to be generalizable to the synthesis of bulk ternary nitride materials.

Ternary nitride materials hold promise for many optical, electronic, and refractory applications; yet, their preparation via solid-state synthesis remains challenging. Often, high pressures or reactive gases are used to manipulate the effective chemical potential of nitrogen, yet these strategies require specialized equipment. Here, we report on a simple two-step synthesis using ion-exchange reactions that yield rocksalt-derived MgZrN2 and Mg2NbN3, as well as layered MgMoN2. All three compounds show almost temperature-independent and weak paramagnetic responses to an applied magnetic field at cryogenic temperatures, indicating phase-pure products. The key to synthesizing these ternary materials is an initial low-temperature step (300–450 °C) to promote Mg-M-N nucleation. The intermediates then are annealed (800–900 °C) to grow crystalline domains of the ternary product. Calorimetry experiments reveal that initial reaction temperatures are determined by phase transitions of reaction precursors, whereas heating directly to high temperatures results in decomposition. These two-step reactions provide a rational guide to material discovery of other bulk ternary nitrides.

The layered Ruddlesden−Popper derivatives of CH 3 NH 3 PbI 3 have recently emerged as high-performing materials for photovoltaics with improved stability. The inclusion of organic molecules within the inorganic framework provides additional dynamic degrees of freedom that influence the optoelectronic properties. The rotational dynamics of CH 3 NH 3 + influence dielectric behavior and electronic excited-state dynamics in CH 3 NH 3 PbI 3 ; however, the influence of cation dynamics on properties in the layered derivatives has not yet been determined. We employ quasi-elastic neutron scattering to study the rotational dynamics of methylammonium (CH 3 NH 3 + , MA) and deuterated nb u t y l a m m o n i u m ( + CD (CD ) NH 3 2 3 3 , d -n B A ) i n ( d -nBA) 2 (MA) n−1 Pb n I 3n+1 (n = 2, 3). (d-nBA) 2 (MA) 2 Pb 3 I 10 exhibits shorter residence times of the CH 3 NH 3 + and + CD (CD ) NH 3 2 3 3 reorientational motions, which are attributed to the larger volumes that the cations occupy in the inorganic framework and to the dimensionality of the inorganic layer by way of dielectric screening between the organic cations. Discontinuities in the mean-squared displacement of overall hydrogen motion determined by fixedwindow elastic neutron scattering are consistent with phase transitions observed by differential scanning calorimetry and timeresolved microwave conductivity signals. Determining how the dimensionality of the inorganic layer influences the organic cation rotational dynamics provides fundamental chemical insight into how the electronic dynamics vary between n-members.

A low-temperature synthesis of iron selenide using molten triphenylphosphine demonstrates the use of an organic flux in solid-state synthesis.

Ternary nitrides with strong metal-nitrogen bonds are an emerging class of inorganic materials for use in a variety of optical, electronic, and refractory applications. However at the elevated synthesis temperatures, entropy favors formation of strong dinitrogen triple bonds, which is often counteracted at high reaction pressures, making synthesis process difficult.Here we report on a simple two-step ion-exchange synthesis of MgZrN 2 and Mg 2 NbN 3 with rocksalt-derived structure as well as the MgMoN 2 with layered hexagonal structure, whereas the corresponding one-step reactions lead to decomposition into binaries. Differential Scanning Calorimetry reveals that the first low-temperature reaction step is facilitated at phase transition temperatures of chloride precursors, which promotes the local ternary Mg−TM−N bond formation. Overall, these results demonstrate a low-temperature ambient-pressure approach to synthesize new ternary nitride materials.