Prof. Dr. Tom Nilges; Fachgebiet Synthese und Charakterisierung innovativer Materialien; (Department Chemie); Foto: Andreas Heddergott /TUM; Verwendung frei für die Berichterstattung über die TUM bei Nennung des Copyrights / Free for use in reporting on TUM, with the copyright noted
Fig.1: Illustration of a pnp-switching material. Picture: V. Hiendl, TUM

Speaker: Prof. Dr. Tom Nilges, Technical University of Munich.

Abstract: Solid ion conductors are fascinating materials for energy conversion and storage applications. Due to their intrinsic properties and especially their high ion mobility in the lattice they are often characterized by complex crystal structures, polymorphism and the loss symmetry during structural phase transitions. This last aspect often causes twinning and demands the collection of precise data and the usage of group-subgroups relations to solve and understand their crystal structures. Beside the structural features of a selection of solid ion conductors discussed in this presentation also intriguing electronic property changes can occur that are closely related to the ion dynamics and structure changes upon heating or cooling of such materials. In this talk we present a series of copper and silver ion conductors that also show reasonable electronic conductivities which characterize them as mixed-conducting semiconductors. An intriguing feature of some of these materials is the ability to change the type of semiconductor mechanism, from a p-type to an n-type and back to p-type while undergoing a reversible structural phase transition.Invented in 2009[1], the first pnp-switching semiconductor Ag10Te4Br3 with a switching temperature of approx. 390 K was the starting point to develop new compounds that show this effect at lower temperatures and in an efficient and applicable way. During the talk the listener will learn about the optimization process and the synthesis strategies that were necessary to lower the pnp-switch down to room temperature and to apply these new compounds as the first position-independent and reversibly switchable diodes.[2] At the end of the presentation the listener will see how compounds like Ag18Cu3Te11Cl3 and AgCuS [3] were utilized to construct reversible diodes (Fig. 1) upon application of a small temperature gradient at room temperature and 360 K.

[1] Reversible switching between p- and n-type conduction in the semiconductor Ag10Te4Br3 Tom Nilges, Stefan Lange, Melanie Bawohl, Jens Markus Deckwart, H.-D. Wiemhöfer, Rodolphe Decourt, Bernard Chevalier, Julia Vannahme, Hellmut Eckert, Richard Weihrich Nature Mater. 8 (2009), 101-108.

[2] A switchable one compound diode Anna Vogel, Alfred Rabenbauer, Philipp Deng, Ruben Steib, Thorben Böger, Wolfgang G. Zeier, Renée Siegel, Jürgen Senker, Dominik Daisenberger, Katharina Nisi, Alexander W. Holleitner, Janio Venturini, Tom Nilges Adv. Mater. 35 (2023), 202370008.

[3] AgCuS: A Single Material Diode with Fast Switching Times Philipp Deng, Alfred Rabenbauer, Kathrin Vosseler, Janio Venturini, Tom Nilges Adv. Funct. Mater. (2023), 202214882.

Series: STOE User Talks 2023

Time: 55 min.

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