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The quasistatic electromechanical and dielectric behaviors of different electroactive actuator materials are investigated under the simultaneous influence of uniaxial stress and temperature at high driving field. An experimental setup capable of applying 9000 newtons of uniaxial force was carefully designed, based on a precisely guided steel frame. Extra caution was taken to minimize the effects of mis-alignment and contact surface clamping. The materials examined in this study include a prospective PLSnZT antiferroelectric ceramics which is currently under development, as well as electrostrictive ceramics, namely PMN-PT 90/10 and PMN-PT 76/24. To assess the applicability of these materials in real systems, multilayer stacks were assembled and their response to stress and temperature was examined. The overall strain of the PLSnZT composition showed increases with increasing uniaxial stress. This might be the result of re-orientation of antiferroelectric domains under pre-stress. It also showed excellent stability in strain over the temperature range 20 to 75°Cunder stress as high as 100 MPa. In contrast, the electrostrictive ceramics are less dependent on stress than antiferroelectrics but more susceptible to temperature changes.

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The current-voltage characteristics and especially the behaviour of the critical Josephson currents of V-V0,-Pb tunnel junctions are investigated experimentally. The maximum Josephson current and its temperature dependence deviate strongly from the theory. The London penetration depth of the vanadium films is found to be much larger than for pure vanadium but its temperature dependence is as expected from theory. The critical temperatures of the vanadium films are between 4.4 and 5.0 K. The ratio 2A(0)/(kFc) decreases with decreasing critical temperature as in the case of superconductors with paramagnetic impurities. The excess currents in the current-voltage characteristics of the tunnel junctions at low voltages are not related to the critical temperatures of the vanadium films. Die Strom-Spannungs-Kennlinien und besonders das Verhalten des kritischen Josephsonstromes von V-V0,-Pb-Tunnelverbindungen werden experimentell untersucht. Der maximale Josephsonstrom und seine TempcraturabhLngigkeit weichen stark von der Theorie ab. Die Londonsche Eindringtiefe der Vanadinschichten ist wesentlich groBer als die fur reines Vanadin, ihre Temperaturabhiingigkeit stimmt jedoch mit der Theorie uberein. Die kritischen Temperaturen der Vanadinschichten liegen zwischen 4,4 und 6,O K. Das Verhaltnis 2A(O)/(kT,) fallt mit abnehmender kritischer Temperatur, wie es fur den Fall eines Supraleiters mit paramagnetischen Verunreinigungen erwartet wid. Die GroBe der VberschuBstrome in den Strom-Spannungs-Kennlinien der Tunnelverbindungen bei geringen Spannungen hangt nicht systematisch von der kritischen Temperatur der Vanadinschichten ab.