Several metal-organic framework (MOF) materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O₂, CO₂, C₃H₈, NO, H₂, ethanol and methanol in the gas atmosphere and under different test gas humidity conditions. Different sensor configurations were studied in a frequency range of 1 Hz -1 MHz and time-continuous measurements were performed at 1 Hz. The materials did not show any impedance response to O₂, CO₂, C₃H₈, NO, or H₂ in the gas atmospheres, although for some materials a significant impedance decrease was induced by a change of the ethanol or methanol concentration in the gas phase. Moreover, pronounced promising and reversible changes in the electric properties of a special MOF material were monitored under varying humidity, with a linear response curve at 120 °C. Further investigations were carried out with differently doped MOF materials of this class, to evaluate the influence of special dopants on the sensor effect.

The electrical conductivity of Sr_1−xLa_xTiO₃ ceramics (x≤0.4) and single crystals (x≤0.1) was investigated in the temperature range between 19 and 1673 K. The mobility was calculated from the carrier concentration, n, which was determined by Hall measurements as well as by a chemical Ti³⁺ titration. The mobility of the single crystals agrees well with a model originally developed for undoped strontium titanate. At low T and high n scattering by ionized donor centers predominates. Above room‐temperature phonon scattering becomes predominant. Sr_1−xLa_xTiO₃ ceramics follow the same model, but only if they had been previously reduced in water‐free and oxygen‐free hydrogen atmospheres. The behavior during the reducing and cooling process can be explained by a defect chemical model, using a set of constants developed in a former work. However, reduced in water saturated hydrogen the conductivity at low T decreases by decades compared to single‐crystal data and cannot be explained anymore by the above‐mentioned models. In conjunction with impedance spectroscopy experiments it was found, that in this case the electrical behavior of the ceramics is completely governed by grain‐boundary phenomena. These high‐ohmic grain boundaries may be depletion layers, which are formed or annihilated depending on the conditions of the preceding high‐temperature process.