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The progress in ([K.sub.0.44],[Na.sub.0.52],[Li.sub.0.04])[O.sub.3]-based ceramics (KNN) with special emphasis on ([K.sub.0.44],[Na.sub.0.52],[Li.sub.0.04])([Nb.sub.0.84][Ta.sub.0.10],[Sb.sub.0.06])[O.sub.3] (KNN-LT-LS) is described. The studies have shown that KNN-LT-LS ceramics have displayed great promise for lead-free application, even though the temperature dependence of properties and strong sensitivity to processing conditions have remained as the two major challenges.

A new type of flextensional actuator is described that has an electromechanically active element that is a piezoelectric-electrostrictive monolithic bi-layer composite (PE-MBLC) capped by truncated thin brass sheets. The studies have shown that high displacement, modest hysteresis, and asymmetry in the displacement with respect to the polarity of the applied electric field are obtained by superimposing a first-order electromechanical effect on a second-order electromechanical effect.

The fabrication and characterization of single-element ultrasonic transducers with active elements composed of lead-free piezoceramic, 1-3 PZT/polymer composite and PVDF film is described. The acoustic characterization of the transducers showed that a wideband transducer with low insertion loss could be obtained by utilizing the nonlead ([K.sub.0.5][Na.sub.0.5]Nb[O.sub.3])-LiTa[O.sub.3]-LiSb[O.sub.3] (KNN-LS-LT) ceramic transducer.

The substitution of [Ba.sup.2+] cations in a lead-free piezoelectric system of [K.sub.1/2][Na.sub.1/2]Nb[O.sub.3]-LiTa[O.sub.3]-LiSb[O.sub.3] (KNN-LT-LS) with perovskite structure is investigated. The findings suggest that the [Ba.sup.2+]-substituted lead-free piezoelectric ceramic transducer could be used for noninvasive applications of ultrasound in medicine.

The symmetry and design of small, multimode flextensional transducers with active shells are studied. They combine the advantages of small size and low-cost manufacturing with control of the shape of the acoustic radiation/receive pattern.

Epitaxial and oriented paraelectric thin films of [Ba.sub.0.60][Sr.sub.0.40]Ti[O.sub.3] are grown on oriented NdGa[O.sub.3] orthorhombic substrates and the nonlinear dielectric properties are studied at GHz along selected inplane crystallographic directions. The in-plane anisotropy and the associated unorthodox, nonlinear dielectric response are obtained by the judicious choice of the epitaxial conditions, which enables to manipulate misfit dislocation phenomena.

A detailed snapshot of the materials used, and a detailed account of the major innovative methods developed in making various piezoelectric ceramic-polymer composites are presented. Computer-aided design (CAD)-based fabrication methods, which result in composites whose structural complexity surpass that of composites obtained with traditional methods are described.

A two-dimensional analytical model of a spiral-shaped piezoelectric ceramic actuator is described and discussed.

A dome actuator using a tangentially alternating poling direction and electric field has been shown to have larger displacement and force responses than actuators with other directions and fields. The proposed design significantly optimizes electromechanical devices.