Functional transition metal nitrides

过渡金属氮化物因其丰富的重要性能和应用，如硬质陶瓷磨料、催化剂、巡回和定域电子的磁性、显著的介电性和可能的铁电性，以及半导体、超导体和锂离子导体的有用输运性质，在现代固体化学和材料科学中发挥着重要的作用。然而，由于氮化物化学热力学的困难，新材料的发现目前停滞不前。在前期工作中，我们提出了通过高压合成新型氮化物如钙钛矿型LaReN3和高度氧化的硝酸铁酸盐Ca4FeN4来解决制备困难的方法。在这个艾美奖-诺醚项目，功能过渡金属氮化物，我们系统地探索氮化物金属氮酸盐和氮化物钙钛矿的常压和高压合成方法。我们使用大容量压力机直接合成富氮材料，如氮化物钙钛矿、鲁德尔斯登-波普尔相和高度氧化的金属氮酸盐。我们继续用常压方法探索贫氮系统，并将重点放在缺陷钙钛矿和Ruddelsden-Popper类型上。在极端的氮气压力下，这些缺陷相将在金刚石顶压室中进一步局部氮化。由于过渡金属氮化物的电子性质是由金属-氮键的共价性决定的，我们预计会有一种与氧化物非常不同的独特的材料化学。钙钛矿氮化物在组成上提供了很大的灵活性，因此可以调整和探索电子相关引起的性质，如输运和磁性。特别是研究了自旋-轨道耦合、电子-声子耦合和晶格自由度的相互作用及其对结构和性质的影响。化学取代将被用来调整价电子组态，以研究金属-绝缘体转变中氮化物的物理。在金属氮酸盐化学中，我们追求氮化物中高氧化态的稳定，并研究其结构化学和性质。开壳系统有望表现出有趣的巡回或局域电子磁性行为，而闭壳系统通常是半导体，这可能有助于能量转换应用。这个Emmy-Noether项目将具有挑战性的无机合成与固体物理的先进分析方法相结合，创建了氮化物研究的一个新的跨学科领域。目标材料提供了一个独特的机会来提高对氮化物的基本理解，其结果将引起无机化学、材料科学和固体物理的所有领域的兴趣。

Transition metal nitrides play a central role in modern solid-state chemistry and materials science owed to abundant important properties and applications such as hard ceramic abrasives, catalysts, magnetism of itinerant and localized electrons, remarkable dielectricity and proposed ferroelectricity, as well as useful transport properties of semiconductors, superconductors, and Li-ion conductors. However, the discovery of new materials is currently stagnating owed to the difficult thermodynamics of nitride chemistry. In preliminary work, we presented a solution to the preparative difficulties through high-pressure synthesis of novel nitrides such as perovskite LaReN3 and highly oxidized nitridoferrate Ca4FeN4. In this Emmy-Noether programme, Functional Transition Metal Nitrides, we systematically explore nitridometallates and nitride perovskites with ambient and high-pressure synthesis methods. We employ large-volume-presses for direct synthesis of nitrogen-rich materials such as nitride perovskites, Ruddelsden-Popper phases, and highly oxidized nitridometallates. We continue exploration of nitrogen-poor systems with ambient pressure methods, and emphasize will be put on defect perovskite and Ruddelsden-Popper types. These defect phases will be further topotactically nitrided in diamond anvil cells under extreme nitrogen pressures. As the electronic properties of transition metal nitrides are governed by the covalency of the metal-nitrogen bonds, we expect a unique materials chemistry much different from oxides. Perovskite nitrides offer a large flexibility in compositions so that properties such as transport and magnetism stemming from electron correlation can be tuned and explored. Especially, the interplay of spin-orbit coupling, electron-phonon coupling, and lattice degrees of freedom and their effect on structure and properties will be studied. Chemical substitutions will be used to tune valence electron configuration to investigate the physics of nitrides at the metal-insulator transition. In nitridometallate chemistry, we pursue the stabilization of high oxidation states in nitrides and investigate their structural chemistry and properties. Open-shell systems are expected to show interesting itinerant or localized electron magnetic behaviour, while closed-shell systems are usually semiconductors, which may be useful for energy conversion applications. This Emmy-Noether project combines challenging inorganic synthesis with advanced analysis methods from solid-state physics to create a new interdisciplinary field of nitride research. The targeted materials present a unique opportunity to improve the fundamental understanding of nitrides and the results will be of interest to all fields of inorganic chemistry, materials science, and solid-state physics.