PIEZOELECTRIC SHEAR MODE DEVICES

摘要

A piezoelectric device (10) comprises a plurality of piezoelectric elements (1) coupled together, each piezoelectric element (1) comprising a unitary member (2) of piezoelectric material having a plurality of portions (6, 8) including at least one active portion (6) and at least one further portion (8). The at least one active portion (6) has a pair of electrodes (4) on opposed surfaces for creating an electric field therebetween on activation by application of an activation voltage across the electrodes (4) and has a polarisation direction for activation in shear mode to create relative displacement between two coupling portions of the member. The piezoelectric elements (1) are coupled together by said coupling portions in series to combine the relative displacement created by each element (1) on activation. In one arrangement, there are at least two further portions which are inactive (8) and constitute said coupling portions, and there is an active portion (6) intermediate each pair of adjacent coupling portions. In another arrangement, the active portions (56) of the members (51) constitute said coupling portions, and there are further portions (58) intermediate the coupling portions which are either inactive or are active and operable in shear mode to shear in an antiparallel direction to the coupling portions.