Compositions – Piezoelectric
Patent
1995-05-30
1997-01-21
Bonner, Melissa
Compositions
Piezoelectric
501134, 501152, C04B 35491
Patent
active
055956777
ABSTRACT:
PLZT piezoelectric ceramics having the general formula (Pb.sub.1-x La.sub.x)(Zr.sub.y Ti.sub.1-y).sub.1-(x/4) O.sub.3 are fabricated in a hot forging process using PbO, TiO.sub.2, ZrO.sub.2, and La.sub.2 O.sub.3 powders as starting materials with Nb.sub.2 O.sub.5 added to provide niobium (Nb) as a dopant. The ZrO.sub.2 and TiO.sub.2 powders are mixed at a molar ratio of y/(1-y), calcined at approximately 1300.degree.-1500.degree. C., ball milled in acetone, and evaporated to a dry powder. The mixture of ZrO.sub.2 and TiO.sub.2 is then combined with the PbO, La.sub.2 O.sub.3, and Nb.sub.2 O.sub.5 powders, and the new mixture is ball milled in acetone, evaporated to a dry powder, calcined at approximately 700.degree.-850.degree. C., and sifted to obtain a particle size of approximately 0.3-2.0 .mu.m. The final PLZT powder is formed into the desired shape by cold pressing followed by sintering at approximately 1000.degree.-1150.degree. C. in oxygen. The PLZT ceramic material is further densifted to about 98.5% of the material's theoretical maximum density by heating to approximately 1175.degree.-1275.degree. C. at 800-1200 psi uniaxial pressure. The resulting high performance Nb-doped PLZT piezoelectric ceramic exhibits an average grain size of about 3 .mu.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.sub.33) greater than 750, maximum strain greater than 0.15%, and a fatigue life of at least 10.sup.10 cycles.
REFERENCES:
patent: 5364710 (1994-11-01), Hikita
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Murty et al, "Effect of Nb (5+) substitution on the piezoelectric properties of PLZT ceramics. Ferroelectrics (1991), 119(1-4), "pp. 119-122.
Neurgaonkar et al., "Properties of Dense PLZT Piezoelectrics," Journal of Intelligent Material Systems and Structures, vol. 4, pp. 272-275 (Apr. 1993).
Nelson Jeffrey G.
Neurgaonkar Ratnakar R.
Oliver John R.
Bonner Melissa
McFarren John C.
Rockwell International Corporation
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