Todd Paul K, Fallon M Jewels, Neilson James R, Zakutayev Andriy
Material Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States.
ACS Mater Lett. 2021 Nov 2;3(12):1677-1683. doi: 10.1021/acsmaterialslett.1c00656. eCollection 2021 Dec 6.
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 MgZrN and MgNbN, as well as layered MgMoN. 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.
三元氮化物材料在许多光学、电子和耐火材料应用中具有潜力；然而，通过固态合成制备它们仍然具有挑战性。通常，需要使用高压或反应性气体来控制氮的有效化学势，但这些策略需要专门的设备。在此，我们报道了一种使用离子交换反应的简单两步合成法，该方法可生成岩盐衍生的MgZrN和MgNbN以及层状MgMoN。这三种化合物在低温下对施加的磁场都表现出几乎与温度无关的微弱顺磁响应，表明产物为纯相。合成这些三元材料的关键是初始低温步骤（300 - 450°C）以促进Mg - M - N成核。然后将中间体退火（800 - 900°C）以生长三元产物的晶畴。量热实验表明，初始反应温度由反应前体的相变决定，而直接加热到高温会导致分解。这两步反应为发现其他块状三元氮化物材料提供了合理的指导。
