High temperature, high strain piezoelectric compositions

Abstract

PLZT piezoelectric ceramics having the general formula (Pb,La,)(Zr,Ti,),M,O,are fabricated in a hot forging process using PbO, TiO,, ZrO,, and La,O,powders with Nb,O,and Ta,O,added to provide 2.0-3.0% Nb,(mole %) and 2.0-3.0% Ta,(mole %) as a dopant. ZrO,and TiO,powders are mixed at a molar ratio of y/(1−y), the preferred molar ratio being 55/45, calcined at approximately 1300° C.-1500° C., ball milled in acetone, and evaporated to a dry powder. The mixture of ZrO,and TiO,is then combined with PbO,, La,O,, Nb,O,and Ta,O,powders, and the new mixture is ball milled in acetone, evaporated to a dry powder, calcined at approximately 700°-850° C., and sifted to obtain a particle size of approximately 0.5-1.5 &mgr;m. The final Nb/Ta-doped PLZT powder is formed into the desired shape by cold pressing followed by sintering at approximately 1000° C.-1150° C. in oxygen. The PLZT ceramic material is further densified to about 98.5% of the material's theoretical maximum density by heating to approximately 1175° C.-1275° C. at 300-1200 psi uniaxial pressure. The resulting high temperature, high performance Nb/Ta-doped PLZT piezoelectric ceramic exhibits an average grain size of about 3 &mgr;m, a well-defined polarization hysteresis loop, reduced strain hysteresis with the application of a unipolar electric field, a breakdown strength greater than 25 kV/cm, a linear piezoelectric coefficient (d,) of about 790 pC/N, maximum strain greater than 0.16%, and a fatigue life of at least 10,cycles and a Tc of about 205-208° C.