High temperature, high strain piezoelectric compositions

• Main Authors: NELSON JEFFREY G, NEURGAONKAR RATNAKAR R
• Format: Patent
• Language: English
• Published: 28.08.2001
• Edition: 7
• Subjects: ARTIFICIAL STONE; CEMENTS; CERAMICS; CHEMISTRY; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDINGMATERIALS; CONCRETE; ELECTRICITY; LIME, MAGNESIA; METALLURGY; REFRACTORIES; SLAG; TREATMENT OF NATURAL STONE

PLZT piezoelectric ceramics having the general formula (Pb1-xLax)(ZryTi1-y)1-(x/4)-zMa+4z/a O3 are fabricated in a hot forging process using PbO, TiO2, ZrO2, and La2O3 powders with Nb2O5 and Ta2O5 added to provide 2.0-3.0% Nb5+ (mole %) and 2.0-3.0% Ta+5 (mole %) as a dopant. ZrO2 and TiO2 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 ZrO2 and TiO2 is then combined with PbO2, La2O3, Nb2O5 and Ta2O5 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 mum. 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 mum, 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 (d33) of about 790 pC/N, maximum strain greater than 0.16%, and a fatigue life of at least 108 cycles and a Tc of about 205-208° C.