2020, Abdelhameed, A.H., Angloher, G., Bauer, P., Bento, A., Bertoldo, E., Breier, R., Bucci, C., Canonica, L., D’Addabbo, A., Di Lorenzo, S., Erb, A., Feilitzsch, F.V., Iachellini, N.F., Fichtinger, S., Fuchs, D., Fuss, A., Ghete, V.M., Garai, A., Gorla, P., Hauff, D., Ješkovský, M., Jochum, J., Kaizer, J., Kaznacheeva, M., Kinast, A., Kluck, H., Kraus, H., Langenkämper, A., Mancuso, M., Mokina, V., Mondragon, E., Olmi, M., Ortmann, T., Pagliarone, C., Palušová, V., Pattavina, L., Petricca, F., Potzel, W., Povinec, P., Pröbst, F., Reindl, F., Rothe, J., Schäffner, K., Schieck, J., Schipperges, V., Schmiedmayer, D., Schönert, S., Schwertner, C., Stahlberg, M., Stodolsky, L., Strandhagen, C., Strauss, R., Usherov, I., Wagner, F., Willers, M., Zema, V., Zeman, J., Brützam, M., Ganschow, S.

In this work, a first cryogenic characterization of a scintillating LiAlO 2 single crystal is presented. The results achieved show that this material holds great potential as a target for direct dark matter search experiments. Three different detector modules obtained from one crystal grown at the Leibniz-Institut für Kristallzüchtung (IKZ) have been tested to study different properties at cryogenic temperatures. Firstly, two 2.8 g twin crystals were used to build different detector modules which were operated in an above-ground laboratory at the Max Planck Institute for Physics (MPP) in Munich, Germany. The first detector module was used to study the scintillation properties of LiAlO 2 at cryogenic temperatures. The second achieved an energy threshold of (213.02 ± 1.48) eV which allows setting a competitive limit on the spin-dependent dark matter particle-proton scattering cross section for dark matter particle masses between 350MeV/c2 and 1.50GeV/c2. Secondly, a detector module with a 373 g LiAlO 2 crystal as the main absorber was tested in an underground facility at the Laboratori Nazionali del Gran Sasso (LNGS): from this measurement it was possible to determine the radiopurity of the crystal and study the feasibility of using this material as a neutron flux monitor for low-background experiments. © 2020, The Author(s).

2021, Porz, L., Knez, D., Scherer, M., Ganschow, S., Kothleitner, G., Rettenwander, D.

High power solid-state Li batteries (SSLB) are hindered by the formation of dendrite-like structures at high current rates. Hence, new design principles are needed to overcome this limitation. By introducing dislocations, we aim to tailor mechanical properties in order to withstand the mechanical stress leading to Li penetration and resulting in a short circuit by a crack-opening mechanism. Such defect engineering, furthermore, appears to enable whisker-like Li metal electrodes for high-rate Li plating. To reach these goals, the challenge of introducing dislocations into ceramic electrolytes needs to be addressed which requires to establish fundamental understanding of the mechanics of dislocations in the particular ceramics. Here we evaluate uniaxial deformation at elevated temperatures as one possible approach to introduce dislocations. By using hot-pressed pellets and single crystals grown by Czochralski method of Li6.4La3Zr1.4Ta0.6O12 garnets as a model system the plastic deformation by more than 10% is demonstrated. While conclusions on the predominating deformation mechanism remain challenging, analysis of activation energy, activation volume, diffusion creep, and the defect structure potentially point to a deformation mechanism involving dislocations. These parameters allow identification of a process window and are a key step on the road of making dislocations available as a design element for SSLB.

2020, Bertoldo, E., Abdelhameed, A.H., Angloher, G., Bauer, P., Bento, A., Breier, R., Bucci, C., Canonica, L., D’Addabbo, A., Di Lorenzo, S., Erb, A., Feilitzsch, F.V., Ferreiro Iachellini, N., Fichtinger, S., Fuchs, D., Fuss, A., Gorla, P., Hauff, D., Ješkovský, M., Jochum, J., Kaizer, J., Kinast, A., Kluck, H., Kraus, H., Langenkämper, A., Mancuso, M., Mokina, V., Mondragon, E., Olmi, M., Ortmann, T., Pagliarone, C., Palušová, V., Pattavina, L., Petricca, F., Potzel, W., Povinec, P., Pröbst, F., Reindl, F., Rothe, J., Schäffner, K., Schieck, J., Schipperges, V., Schmiedmayer, D., Schönert, S., Schwertner, C., Stahlberg, M., Stodolsky, L., Strandhagen, C., Strauss, R., Usherov, I., Willers, M., Zema, V., Zeman, J., Brützam, M., Ganschow, S.

In the current direct dark matter search landscape, the leading experiments in the sub-GeV mass region mostly rely on cryogenic techniques which employ crystalline targets. One attractive type of crystals for these experiments is those containing lithium, due to the fact that 7Li is an ideal candidate to study spin-dependent dark matter interactions in the low mass region. Furthermore, 6Li can absorb neutrons, a challenging background for dark matter experiments, through a distinctive signature which allows the monitoring of the neutron flux directly on site. In this work, we show the results obtained with three different detectors based on LiAlO2, a target crystal never used before in cryogenic experiments.

2019, Von Helden, L., Bogula, L., Janolin, P.-E., Hanke, M., Breuer, T., Schmidbauer, M., Ganschow, S., Schwarzkopf, J.

We present a study in which ferroelectric phase transition temperatures in epitaxial KxNa1-xNbO3 films are altered systematically by choosing different (110)-oriented rare-earth scandate substrates and by variation of the potassium to sodium ratio. Our results prove the capability to continuously shift the ferroelectric-to-ferroelectric transition from the monoclinic MC to orthorhombic c-phase by about 400 °C via the application of anisotropic compressive strain. The phase transition was investigated in detail by monitoring the temperature dependence of ferroelectric domain patterns using piezoresponse force microscopy and upon analyzing structural changes by means of high resolution X-ray diffraction including X-ray reciprocal space mapping. Moreover, the temperature evolution of the effective piezoelectric coefficient d33,f was determined using double beam laser interferometry, which exhibits a significant dependence on the particular ferroelectric phase. © 2019 Author(s).