Effect of different processing parameters on preparation of doped soft PZT powders and fabrication of multilayered stacks

The use of piezoelectric materials for actuator applications has been steadily increasing in recent years. For better performance, actuators should-be fabricated from PZT materials of high d33 values and from large number of thin strips. PZT compositions near morphotropic phase boundary (MPB) with donor dopants are generally selected to get high piezo properties. In view of the above, we have studied the compositions Pb,-x, Mx -Pos3Ti o.47) 03,w here M = ~ a (0~-8 'm ole %), ~ d(0-~6 m+ole %), s?' (0-3 mole %) and their combinations. The powders were prepared by wet chemical method using clorides and nitrates as precursors. The powders were calcined in the temperature range\ud af 650-900°C, pelletized and sintered in the temperature range of 1050-1250°C. The effect of different dopants as well as the effect of calcination and sintering temperatures\ud on piezo- properties was studied. The sintered pellets were electroded, poled and were characterized for piezoelectric charge coefficient (d33), capacitance and loss factor with\ud an operating frequency of 100Hz at room temperature. The dielectric constants of the samples were calculated from the measured capacitance values. From the above study,\ud maximum dJ3 value of 234 pC/N for 2 mole% ~ a ~2'6,0 pC/N for 2 mole% ~d~~ and ZE pC/N for 1 mole% s?' were obtained. Similarly, in case of combined dopants, a combination of 1 mole%Nd and~ 1 m+ole % sr2+p roduced a maximum d33 value of 313 IJCIN. PZT powders were uniaxially pressed in the form of rectangular blocks, sintered in a lead rich atmosphere, cut into thin strips of equal sizes and were leveled, polished, W o d e d and poled in a dc field of 2KV/mm. PZT stacks were fabricated by stacking by layering them ensuring the desired electrical connectivity. The static displacements of the stacks were measured by applying a dc voltage and were recorded bg a strain gauge of lpm resolution and the % free strain was calculated. The maximum displacement of 20pm was recorded at an applied voltage of 650V. The effective inverse piezoelectric coefficient (d33) of the stacks in the direction of the applied field were 5dcdated by using the relation d33=&t/ (nV), where 'at" is the displacement, "V" is the applied voltage and "n" is the number of the active piezoelectric layers in the actuator. The fiee strain was 0.1% and the inverse d33 coefficient was 11 50x10-l2 mN respectively at 650V. Further studies on effect of thickness of PZT layers as well as number of layers on displacement are under progress.\u