The correlation between electrical and mechanical losses in ferroelectric ceramics has been investigated theoretically and experimentally. The theoretical derivation is based on the assumption that both loss types are induced by 90° domain walls moving under the influence of electrical or mechanical fields. A proportionality between both loss types is found. The factor of proportionality includes material constants such as spontaneous polarization and striction, permittivity, and elastic compliance, but is independent of the specific energy dissipation mechanism of a moving domain wall. In a compositional series of differently doped PLZT ceramics with a broad range of losses the theoretically derived relations have been checked experimentally. Good agreement between the experimental and theoretical results was found.

The oscillation of domain walls caused by alternating fields is often thought to be the origin of dielectric losses. In this paper the physical nature of losses is explained by the damping of moving 90° domain walls. For frequencies up to 108 Hz the origin of damping of the wall motion is ascribed to point defects within the 90° domain wall. At high frequencies damping results from the reflection of thermal-lattice waves impinging on a moving 90° domain wall.

Ba1–xSrxTiO3 ceramics and SrTiO3 single crystals subjected to reducing treatment show‐weight losses due to the release of oxygen. In parallel the reduction causes an electrical conductivity which is proportional to the weight loss. On the justified assumption that oxygen vacancies occur during the reduction process and that each vacancy loses an electron to the conduction band at room temperature, it is possible to determine from the weight‐loss measurements the number of electrons and, in combination with the electrical conductivity, their mobility. The mobility thus determined is 0.6 cm2/Vs for BaTiO3, rising with increasing Sr concentration to 5.9 cm2/Vs for SrTiO3. These gravimetrically determined mobilities are in satisfactory agreement with those found from Hall‐effect and thermo‐electric power measurements.

Thermokraft, elektrische Leitfähigkeit und HAix-Effekt unterschiedlich dotierter n-und p-leitender LaCo03-Proben wurden über einen größeren Temperaturbereich gemessen. Die Meßergebnisse konnten mit dem Modell des "kleinen Polaron" gedeutet werden, nach dem die Transporteigenschaften durch thermisch aktivierte Platzwechsel der Ladungsträger zwischen benachbarten lokali- Im Bereich der Energielücke zwischen diesen breiten Bändern sind nun die schmalen nicht überlap-penden 3d-Teilbänder (bzw. Folgen atomarer 3d-Terme) angeordnet. Dabei ist im Kristall die Entartung der 3d-Terme wenigstens teilweise aufgehoben. Von diesen schmalen 3d-Bändern interessieren hier jedoch nur das energetisch höchstgelegene der besetzten und das energetisch tiefste der unbesetzten Bänder, welche in Abb. 1 eingezeichnet sind. Die im folgenden beschriebenen Halbleitereigenschaften des LaCo03 spielen sich in diesem inneren Bänder-schema der 3d-Elektronen ab. Die Energieabstände zwischen diesen schmalen 3d-Bändern und den breiten Bändern V und L sind hier derart groß, daß die thermisch angeregte Ladungsträgerdichte in den Bändern V und L vernachlässigbar ist.1 E.

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