Scientific Highlights

3 mai 2019

An iodine polymeric chain with tunable conductivity

The progressive hydrostatic compression of I2 and I3- units in an organic salt lead to a homoatomic polymeric chain. As the I---I distance collapses the covalent character of the interaction becomes more relevant, leading to a pressure-tunable increased conductivity.

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1 avril 2019
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HERCULES school 2019 at SLS

In the week of April 1-5 PSI welcomes 20 PhD students and postdocs taking part in the European HERCULES 2019 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.

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12 mars 2019
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Additive Manufacturing of High Entropy Alloys

Additive manufacturing of high-entropy alloys combines the mechanical properties of this novel family of alloys with the geometrical freedom and complexity required by modern designs. An approach to additive manufacturing of high-entropy alloys has been developed based on 3D extrusion of inks containing a blend of oxide nanopowders (Co3O4 + Cr2O3 + Fe2O3 + NiO), followed by co-reduction to metals, inter-diffusion and sintering to near-full density CoCrFeNi in H2. A complex phase evolution path is observed by in-situ X-ray diffraction in extruded filaments: the oxide phases undergo reduction and the resulting metals inter-diffuse, ultimately forming the desired fcc-CoCrFeNi alloy (see figure). Linked to this phase evolution is a complex micro-structural one, from loosely packed oxide particles to fully-annealed, metallic CoCrFeNi with 99.6 ± 0.1% relative density. CoCrFeNi micro-lattices are created with strut diameters as low as 100 μm and excellent mechanical properties at ambient and cryogenic temperatures.

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5 septembre 2018
Figure 1 (a) Transient relative x-ray intensity of the (1.5 0.5 0.5) superlattice reflection of Sr0.97Ca0.03TiO3 upon above bandgap excitation with 40 fs pulses Inset: STO crystal structure as seen along the c-axis. phi measures the antiferrodistortive rotation of the oxygen octahedra (exaggerated) and represents the order parameter. (b) Calculated energy change per STO cubic unit cell as a function of oxygen displacement u/u0 along the in-plane cubic crystal axes resulting from the octahedral rotation at …

Moving Atoms by Photodoping

Understanding how and how fast we can drive atoms to create a structural phase transition is of fundamental interest as it directly relates to many processes in nature. Here we show that a photoexcitation can drive a purely structural phase transition before the energy is relaxed in the material that corresponds to a “warmer” equilibrated state.

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