Intermolecular vibrations in pure and doped C60

We discuss the results of inelastic neutron time-of-flight spectroscopy on powder samples of C₆₀, K₃C₆₀ and Rb₃C₆₀. A well structured density of states is obtained from the raw data where the details can be attributed to translational acoustic/optic and librational modes. The intermolecular excitation spectra for all three compounds can be well understood within the frame-work of lattice dynamics of a molecular crystal. We show that a particular sample preparation is necessary to avoid impurity contributions in particular within the gap region between inter- and intramolecular vibrations. There are indications for a weak anomalous temperature dependence of low energy phonons in K₃C₆₀ atT _c .     

Sol-gel preparation of selected high temperature proton conductors

The sol-gel preparation of the compounds BaCe_0.8Y_0.2O_2.9 (BCY20), BaCe_0.8Gd_0.2O_2.9 (BCG20), BaTiO₃, BaTi_0.9Y_0.1O_2.95 and BaTi_0.9Er_0.1O_2.95 using the acrylamide route is described. The advantages lie in the short reaction time leading to the gels and the large batch sizes possible. In the case of the titanates there was the additional advantage that one of the starting compounds was metallic Ti powder which was dissolved in H₂O₂ and NH₃. Basically, all 5 compounds could be synthesized phase pure. The cerates were well described by PDF 35-1318 and absorb large quantities of water vapor in TG experiments. The doped titanates were cubic and were well characterized by PDF 31-0174. They only absorb relatively small amounts of water vapor but still may be termed proton conductors.     

Einige neue Laboratoriumsapparate

Analytical and Bioanalytical Chemistry -