Prof. Jürgen Rödel, TU Darmstadt, CeramicsGroup, Germany: New processing approaches: dislocation-tuned functionality and black light sintering of ceramics

Prof. Dr. Jürgen Rödel

Bernhard-Ilschner- Hörsaal (H14), Martensstr. 5-7, Erlangen

TU Darmstadt, Ceramics Group, Germany
New processing approaches: dislocation-tuned functionality and black light sintering of ceramics

This talk will consider very new topics with the first papers in this field from either 2021 or 2022. These topics open new research fields and I will illustrate opportunities for the next 5 to 20 years, some for basic science and some for application.

The common theme is that I will discuss new microstructural tools or new processing methods to get completely new properties.

Dislocations in polycrystalline and single-crystal ceramics are usually present in very low density. However, they are appealing as they are typically charged and can be used both as paths as well as barriers for electric current, they can pin domain walls [1] and can be scattering centers. A special advantage of using dislocations to 1-dimensionally dope ceramics lies in the fact that they are temperature-stable and sustainable (no additional element needed) [2]. I will highlight examples on electrical conductivity in TiO2 [3], interaction with domain walls in BaTiO3 [1], toughening in SrTiO3 [3] and photoconductivity [4]. Depending on status of patent applications, I will outline the various options of dislocation catalysis for production of materials needed for sustainability.

We developed black light sintering, because we were searching for a process to insert dislocations during sintering. To heat very fast, we used photon energies above the band gap and can now sinter materials in very few seconds without electrical contact and without container. While we failed to insert dislocations, the energy savings as compared to standard heating in furnaces are drastic [5]. The process has been demonstrated on several materials and funding was obtained by SPRIND and ESA. One of my former PhD students has formed a company with several industry contacts and one of my group leaders with one of my current students covers the fundamental aspects.

References:

[1] M. Höfling, JR et al., “Control of polarization in bulk ferroelectrics by mechanical dislocation imprint,” Science, 372, 961-964 (2021)

[2] Q.K. Muhammad, JR et al., „Donor and acceptor-like self-doping by mechanically induced dislocations in TiO2“, nano energy, 85, 105944 (2021)

[3] Lukas Porz, JR et al., „Dislocation-toughened ceramics“, Materials Horizons, 8, 1528-1537 (2021)

[4] Maximilian Kissel, JR et al., “Enhanced photoconductivity at dislocations in SrTiO3”, Adv. Mat., 2203032 (2022)

[5] Lukas Porz, JR et al., “Blacklight sintering of ceramics”, Materials Horizons, 9, 1717-1726 (2022)