Perovskite solid solutions exist throughout the ternary system Pb(Mn3+ 1/2NU1/2)O3-PUTiO3 PbZrO3 and in up to 40mol% of the first component in Pb(Mn2+ 1/3Nb2/3)O3-PbTiO3-PbZrO3; at higher concentrations, a mixture of perovskite and pyrochlore phases was obtained. With Pb(Mn2+ 1/3Nb2,a)O3, ceramics showed enhanced piezoelectric activity and increased mechanical quality factor, both in comparison to the PbTiO3-PbZrO3 binary and with Pb(Mn3+ 1/2Nb1/2)O3. Much improved piezoelectric properties were obtained, when manganese ions were regarded as divalent ions, in comparison with the case of trivalent ions. The difference seems to be caused by different amount of space charge generated in the ceramics, resulting from the co-existence of manganese ion and niobium ion. The amount in the former ceramics is much larger than that of the latter. The Curie point and electrical resistivity of these ceramics remain sufficiently high for practical use.
Very pure lead zirconate titanate ceramics were prepared for an accurate determination of the characteristic values of piezoelectric properties. The ceramics were sufficiently matured by using pulverized calcined powders and by sintering with a gradual rise in temperature. Electromechanical activity of the ceramics became maximum when the ceramics were subected to poling at 100•Ž with a field intensity of 40 kV/cm for 10 min. Deterioration gave rise to the breakdown of ceramics along grain boundaries when the field intensity and the time of poling increased. Breakdown predominated in the ceramics belonging to tetragonal symmetry. Breakdown seems to be caused by a decrease of intergranular binding strength, and this assumption was confirmed by measurement of the bending strength and observation of the fracture.
A new type of actuator has been developed by multilayering piezoelectric ceramic green sheets with line electrodes in such a way that electrode lines are parallel and slide one-half a pitch in alternate layers. The large displacements were obtained utilizing multiplication of longitudinal converse piezoelectric effect occurs between nearest electrode lines located a layer below or above.A long co-fired multilayer actuator with a large displacement can be easily produced, and reliability was improved by eliminating exposure of opposite polarity of electrodes on a same surface of actuator to humidity in the air. For example, a 74mm long actuator with 106 electrode lines on each of 100 layers provided a displacement of SO pm/3SOV, with a generative force of 350 kg/cm2. Also, under the condition of 8S"C/90%RH and 180V constant loading, a lifetime of over 1000 hr was demonstrated. IhTRODUCTIONWith the recent development of electromechanical devices, piezoelectric actuators have been a primary focus of interest owing to their fast response time, large generative forces, high volumetric efficiency, low cost, and relatively simplistic E-field control. Multilayer piezoelectric actuators offer additional performance features such as low driving voltage and large displacements.In order to avoid delaminations or crack formations, conventional co-fired multilayered actuators which utilize longitudinal piezoelectric effect are limited to a maximum height of approximately 20mm; subsequently, displacement is limited to approximately 1Spm. Therefore, when more than 1 Spm displacement is required, i t is necessary to use displacement magnification devices or simply adhere several multilayer actuators in series. The displacement magnification devices, however, often require complicated design. In addition, they also possess the added disadvantage of decreasing the generative force (which is inversely proportional to the displacement). The problems encountered when using the stacked multilayer actuators are inadequate control of total length as well as a loss of response time due to the existence of adhesive layers.Theoretical analysis and detailed experimental data on piezoelectric resonators with interdigital electrodes on the surface of a rectangular ceramic for both poling and driving purposes are already found in the literatures[1,21. In addition, we have previously developed torsional actuators by applying interdigital electrode at a 45 degree angle on the outside surface of hollow PZT cylinder [3]. In order to develop a large displacement co-fired actuator, we first investigated the effect of several parameters such as electrode line width, gap, and number of layers on the three dimensional interdigital electrodes (3D-IDE). By optimizing above-mentioned parameters we have developed 73mm long cofired piezoelectric actuators which provided displacement of a S0pm at 150V.In addition to the large displacement, the new structure also provides improved reliability by eliminating exposure of internal electrodes on the same surface o...
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