WIN Seminar - Professor Harald Hillebrecht: "Inorganic Energy Materials − Contributions from Solid State Chemistry"

Monday, May 29, 2017 11:00 am - 12:00 pm EDT (GMT -04:00)

The Waterloo Institute for Nanotechnology (WIN) presents a seminar by Professor Harald Hillebrecht, Institute for Inorganic Chemistry, University of Freiburg, Germany.

Inorganic Energy Materials − Contributions from Solid State Chemistry

Contributions from solid state chemistry to inorganic energy materials may originate from two different directions. One aspect is the synthesis and characterization of new compounds for possible applications. Another point is the development of synthetic strategies to obtain well-known materials with enhanced properties or in a more efficient way.
One field for inorganic energy materials are thermoelectrics. Bi1-xSbx (x ≈ 0.15) is the best thermoelectric material at low temperatures around 200 K. Nanoparticles were obtained by a simple and upscalable solution-based process. ZT-values are comparable to material made by mechanical alloying. For high-temperature applications (>1000 K) the solid solution Si1-xGex is obtained by SPS. Homogenous polycrystalline samples can be pressed into pellets which were used as feed rod for the single crystal growth by a floating zone technique in a mirror oven. SPS was also used for a one-step synthesis of BiCuSeO, which is also a promising material for medium temperatures.
Fe2-xCoxAlB2 was established as a new magnetocaloric material where the co-content shifts Tc between 300 K (x = 0) and 200 K (x = 0.3). Similar related ternary borides like Fe3Al2B2, Ru9Al3B8 and Ru9Al5B8-x.
MAX-phases, i.e. ternary carbides or nitrides of the series (MX)nMA (M = Ti, V, Nb, ..; A = Al, Si, Ga, ..; X = C, N; n = 1, 2, 3) are investigated as machinable ceramics, and very recently as material for batteries, catalysts, or capacitors. We have analyzed solid solutions of different representatives of M and A based on single crystal investigations. Similar properties can be expected for analogous ternary borides (MB2)nMA.
Organic-inorganic hybride perovskites like MAPbI3 (MA = CH3NH3) are excellent dyes for the dye-sensitized solar cell. Within a few years the efficiency was increased to over 20%. The combination of two different organic cations like guanidinium (Gu), formamidinium (Fo) or thioformamidinium (Tu) modifies the dimensionality of the framework of edge-sharing PbI6 octahedra to layered structures with varying thickness and topology. This has an impact on optical properties and chemical stabilities. The classification of the crystal structures is similar to oxidic Ruddlesden-Popper phases. Further fragmentation to different 1D structures is possible, but the resulting large band gap prohibits an application.