Expansion of the Chemistry of Nitridometallates of 3d Transition Metals through a Novel High-Pressure Synthesis Approach

• Applicant: Dr. Simon David Kloß
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: from 2019 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 433306733

In this postdoctoral project a new synthesis pathway shall be opened for the hitherto little explored nitridometallates of the 3d transition metals. These compounds of composition A–M–N, in which A is an electropositive metal and M a 3d transition metal, had been investigated in the 90s owing to their potential application as semimetals in spintronics, thermoelectrics, superconductors, and energy conversion materials. Their exploration, however, almost came to a standstill in recent years, which might in part be owed to the difficult synthesis of these materials. Obstacles are inert or temperature labile starting materials and most important the strongly rivalling redox decomposition of the nitrides. At ambient pressures there is only a small temperature window available to conduct reactions due to this decomposition.The nitridometallate chemistry of the 3d metals will be revived with an innovative high-pressure approach in this project. By applying pressures in the gigapascal range the redox decomposition is suppressed following the principle of Le Chatelier and the temperature window is enlarged. Hence, through the enclosed and pressurized reaction space, new synthesis strategies can be realized that are inapplicable at ambient pressures.Firstly, new synthesis routes shall be established through variation of pressure, temperature, as well as different reaction types and starting materials like azides, amides, nitrides and metathesis reactions. Nitridotitanates and -ferrates are chosen as starting systems owing to the physical properties of the 3d metals. Leading questions for the exploration of the nitridometallates are the synthesis of missing members of existing structural families for example Ba2FeN2 of the MFeN2 compounds (M = Ca, Sr), and the synthesis of predicted materials with intriguing properties like the thermoelectric BaTiN2. Long-term goals, which can evolve from this project, include the investigation of the metal-insulator transition in these systems as well as the study of the influence of high pressures and temperatures on the anion structures, since several known nitridometallates feature structural motifs from main group chemistry. In the second part of this project, physical properties like magnetism, resistivity, and heat capacity of obtained compounds will be investigated in dependency on for example temperature and applied magnetic field. As only little is known about such properties, one goal is to enrich the understanding of the structure-property relations of nitridometallates. We are confident that this postdoctoral project can lead to fascinating insights into the structural chemistry as well as the physical properties of the nitridometallates of the 3d transition metals.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. J. Paul Attfield