Synthesis and characterisation of (poly-)antimonides and N-doped ZnO

This thesis focused on the investigation of novel and known materials in the binary system T_xSb_y (T = transition metal) and in the ternary system M_xT_ySb_z (M = Hf, Zr). The compounds were tested as anode materials for lithium-ion-batteries. In addition, the electronic conductivity and the magnetic behavior at low temperatures were tested. Main focus of this work was on the bonding situation in the antimony networks. To compare the results of the characterization of known or novel metallic/covalent compounds, all materials were synthesized and characterized either by solid state synthesis in a muffle furnace or by arc melting. In the ternary system M_xT_ySb_z (M = Hf, Zr; T = Cu, Ni, Pd), all compounds show covalent as well as metallic bonding character. Phase pure Zr₃TSb₇ (T = Ni, Pd) and Zr₂TSb₃ (T = Cu, Pd), were tested as potential anode materials for lithium-ion batteries. During electrochemical cycling these ternary compounds invariably convert to Li₃Sb and the respective transition metals. Magnetic measurements of these materials show typical behaviour of intermetallic compounds. In a ZFC-FC-measurement of Zr₃NiSb₇ a superconductive phase with 2 vol% superconducting material at T_c = 10.9 K could be detected. The low volume superconductivity indicates that a side phase is responsible for this behaviour. Ternary Hf₁₀NiSb₁₈, Zr₅NiSb₉ and Zr₄CuSb₇ were also synthesized by systematic variation of the synthesis conditions. The crystal structures were solved and showed a similar structure to the Hf₅Sb₉ structure type. In the case of Zr₄CuSb₉, phase purity was detected by Xray powder diffraction and the physical properties were measured. Due to ex-situ X-ray powder diffraction it was shown that the compound is disintegrating during lithiation and is re-formed during delithiation up to the 20^th cycle. M_xSb_y (M = Hf, Zr) as representatives of binary antimonides were synthesized. Through Fe and/or Ni doping superconducting Phases have been found. Furthermore binary chromium-antimonides with partial Fe or Ni substitution were prepared. Cr₂Ni_0,3Sb_3,7 was tested as potential anodic material and a capacity of 98% (520 mAh.g^-1) of the theoretical capacity in the 2^nd cycle was measured. All compounds indicated that antimonies with a covalent bonding character are more stable against lithium intercalation than the intermetallic ones. New compounds in the quaternary system Cu-Hg-Sb-X (X = Br, I) were obtained by using the reaction conditions for the earlier (lighter) elements of the V. main group (P, As). In the new structure [Hg₃Sb₂]₄[CuX₃]₄X₂ (X = Br, I) X₂ a barbell of the halide is present. This structure is the first example in the system Hf-Sb-X which shows two different interpenetrated networks: [Hg₃Sb₂]²⁺ and [CuX₃]^2-. For the first time it has been possible to calculate the Br-Br bond length by X-ray single crystal measurements at room temperature. Another topic of this work was to test the solution combustion method (SCM) in order to gain ZnO (Wurtzit structure) with nitrogen defects at the oxygen position. Standard synthesis methods for oxonitrides require high temperature or high pressure procedures. A softer synthesis method is the solution combustion method published by Mapa and Gopinath. The results of various experiments in cooperation with Stefan Soellradl yielded no intercalation of nitrogen defects into ZnO but a new phase was found which is identified as isocyanuric acid after reprocessing.