Amalgams of less noble metals as model systems for polar intermetallic phases

• Applicant: Professor Dr. Constantin Hoch
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429690805

• Final Report Year: 2023

Final Report Abstract

The demands of our time, especially energy generation and storage, require new, highly efficient materials. Optimizing conventional materials is not enough. Exploratory basic research is indispensable for the future requirements. A room-temperature superconductor would be a nice thing, of course. The "up-conversion" of waste heat into electrical energy would also be a big step. Thermo-electrics are materials that convert temperature gradients into electrical voltage, but unfortunately so far only with poor yield. The physical principles of thermo-electrics are well understood, but the chemical conversion into efficient materials is not so simple: a material converting a constant temperature difference into electrical voltage must be at the same time a good electrical and a poor thermal conductor. However, since metals are also good thermal conductors (electrons are responsible for current and also a large fraction of the heat transport), one is not easily compatible with the other. Among the most efficient thermoelectric materials, polar intermetallic phases are particularly striking. However, thermoelectric behavior is only one example of how polar intermetallic phases can be highly interesting for modern applications. Other fields of application would be microelectronics, data storage or quantum computing. In order to find targeted syntheses of polar intermetallic phases with exactly the desired properties, one needs to know precisely the still unclear chemical and structural parameters that have direct influence on the well-understood physical parameters. And this is exactly where this project comes in. Systematic chemical modification of reported materials as well as the targeted preparation of new polar intermetallic phases helped to identify chemical and structural parameters that have a particularly strong influence on the typical properties of polar intermetallic phases, the so-called "bad-metal behavior". Amalgams were already known as particularly suitable for such investigations. Mercury reacts with almost all metals, therefore there are many different and still comparable but chemically quite simple systems. In particular, amalgams of less-noble metals (alkali, alkaline earth or rare earth metals) are typically polar intermetallic phases, with varying degrees of bad-metal behavior. Based on many new amalgams and the comparison with reported ones, we were able to show that the degree of ionic bonding contributions plays a particularly important role and can be varied in a targeted manner, but also structural parameters, such as on the one hand the complexity of the crystal structure and on the other hand the incorporation of disorder within a structure. These parameters can now be transferred from amalgams to polar intermetallic phases in general.

Publications

• Amalgams of less noble metals: Polarity in intermetallic compounds, Anorganisch-Chemisches Seminar der Universität zu Köln (2019).
  C. Hoch
  
• New Solvate Complexes [Be(Solv) 4]I2 of Beryllium Iodide with polar aprotic Solvents, 28. Jahrestagung der Deutschen Gesellschaft für Kristallographie, Leipzig (2019).
  T. Hohl, T. Sinn & C. Hoch
  
• Solvatkomplexe des Berylliums vom Typ [Be(Solv)4]I2, 15. Koordinationschemie-Treffen, LMU München (2019).
  T. Hohl, T. Sinn & C. Hoch
  
• Zwischen den Stühlen: Festkörper zwischen Metallen und Salzen, GDCh-Kolloquium, Uni Halle-Wittenberg (2021).
  C. Hoch
  
• Amalgams of electropositive metals - model systems for polar intermetallic phases, 21st Conference on Inorganic Chemistry, Marburg (2022).
  C. Hoch
  
• Amalgams of electropositive metals - model systems for polar intermetallic phases, URCUP - Undergraduate Research Conference on Molecular Sciences, Kloster Irsee (2022).
  C. Hoch
  
• From binary to ternary amalgams: expanding the structural variety of the Gd14Ag51 structure family, 30. Jahrestagung der Deutschen Gesellschaft für Kristallographie, München - online (2022).
  T. Hohl, L. F. J. S. Nusser, J. Wulfes & C. Hoch
  
• Structure and Bonding in CsNa2Hg18, a New Ternary Amalgam with Strong Coulombic Bonding Contributions. Crystals, 12(11), 1679.
  Hohl, Timotheus; Tambornino, Frank & Hoch, Constantin
  
• The Hg-rich part of the binary system K-Hg revised: synthesis, crystal and electronic structures of KHg 4, KHg5 and KHg8, 33rd European Crystallographic Meeting, Versailles (2022).
  T. Hohl, C. Hoch, M. Wendorff & C. Röhr
  
• Dim lit and overweight: - where X-ray diffraction becomes challenged, Stoe User Meeting, Darmstadt (2023).
  C.Hoch,
  
• Influence of Disorder on the Bad Metal Behavior in Polar Amalgams. Inorganic Chemistry, 62(9), 3965-3975.
  Hohl, Timotheus; Kremer, Reinhard K.; Ebbinghaus, Stefan G.; Khan, Saleem A.; Minár, Ján & Hoch, Constantin
  
• Röntgenstrukturanalyse von Amalgamen: Komplexität, Absorption und andere Widrigeiten, 31. Jahrestagung der Deutschen Gesellschaft für Kristallographie, Frankfurt (2023).
  C. Hoch
  
• Systematische Untersuchung von ternären Amalgamen elektropositiver Metalle – Synthese, Kristallstrukturen und physikalische Eigenschaften, Dissertation, LMU München, 2023.
  T. Hohl
  
• Ternary amalgams: expanding the structural variety of the Gd14Ag51 family. Zeitschrift für Kristallographie - Crystalline Materials, 238(5-6), 187-199.
  Hohl, Timotheus; Nusser, Lukas; Wulfes, Jessica & Hoch, Constantin