Plastic and nonmetallic article shaping or treating: processes – Including step of generating heat by friction
Patent
1995-05-30
1997-03-04
Czaja, Donald E.
Plastic and nonmetallic article shaping or treating: processes
Including step of generating heat by friction
264 65, 264 66, 264122, 264125, 501134, C04B 3549
Patent
active
056076320
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 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 densified 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.
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Nelson Jeffrey G.
Neurgaonkar Ratnakar R.
Oliver John R.
Czaja Donald E.
Rockwell International Corporation
Vincent Sean
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