Characterization of Structure-Property-Relationships of electrical Functional Materials with Solid State-NMR
Prof. Dr. Gerd Buntkowsky (Eduard-Zintl-Institut für Anorganische u. Physikalische Chemie)
Dr. Hergen Breitzke (Eduard-Zintl-Institut für Anorganische u. Physikalische Chemie)
The efficient development of novel electrical functional materials and the study of their fatigue processes necessitate a characterization of these materials on the molecular level. For this reason the spectroscopic expertise of the research group is employed for the study of these materials and their fatigue processes. The focus of the project is on LiSiCN and LixMO2 type materials. In addition also piezo ceramics like of the type (1−x)Bi0.5Na0.5TiO3–xK0.5Na0.5NbO3 are studied.
Depending on the material under investigation 7Li, 59Co, 93Nb, 207Pb and others are employed as spin probes. If necessary the samples are also characterized by 135/137Ba- or 209Bi-NQR. By the quantitative comparison of fresh and fatigued materials the characteristic finger prints of the fatigue effects will be revealed. These are translated into the relevant chemical shift and quadrupolar interaction parameters, which can be interpreted on the molecular level or serve as basis of quantum chemical calculations.
In the case of the LiSiCN ceramics we wish to reveal by 13C-MAS and possibly X/Li_REDOR or X/Li-REAPDOR, how the lithium is bound in the ceramics and their precursors. In the case of the LixMO2-materials these studies as a function of the Co/Ni ratio parallel those with synchrotron radiation or in-situ neutron diffraction performed in TP B4. These studies are completed by 59Co-NMR-measurements. By the combination of the NMR data with the results from TP B4 a complete picture of the fatigue processes is expected.
The mobility of the lithium ions is equally important. If the lithium motions are accompanied by an exchange between chemically or magnetically non-equivalent positions, they are detectable by NMR. Depending on the time scale of the motions MAS-NMR, Spin-Echo-techniques or relaxation measurements are performed.