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A manganese-doped BaTiOa was investigated with regard to the degradation of resistivity under a high d.c. electric field. Degradation was measured as a function of time, composition and temperature, using an electric field of 3 V #m -1. The activation energy of the process was found to be 1.13eV. to clarify the mechanism / against U characteristics and / against Tgraphs of new, degraded and relaxed samples were studied. Electron paramagnetic resonance and potential measurements were found to be useful in describing the degradation. Finally, a brief model is put forward to account for the observed phenomena. It is based on an injection of oxygen vacancies from the anode, which isaccompanied by a reduction of manganese in the lattice.* Based on a thesis submitted by J. R6del for the diploma degree at the

This article gives an overview about the preparation and characterization of asymmetric ceramic membranes that have been developed at our institute within the last years. Depending on the required pore size of the filter active layer for filtration applications ranging from microfiltration (MF) up to nanofiltration (NF) different preparation routes have to be applied.

Ceramics of the melilite‐type compound La1+xSr1−xGa3O7−δ were prepared by conventional ceramic processing. Samples prepared represented the entire homogeneity region of the phase (i.e., x=−0.15 to 0.60). Electrochemical characterization under variable temperature and atmospheric conditions in the vicinity of air entailed four‐point direct‐current conductivity measurements and electromotive force measurements. La1+xSr1−xGa3O7−δ samples exhibited a p‐type behavior with generally increased conductivity with increased substitution of lanthanum for strontium, which reached a saturation value of ∼10−1 S·cm−1 at 950°C.