Thin layer composite unimorph ferroelectric driver and sensor

• US 6,734,603 B2
• Filed: 01/24/1997
• Issued: 05/11/2004
• Est. Priority Date: 04/04/1995
• Status: Expired due to Fees

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The National Aeronautics And Space Administration
• Inventors: Fox, Robert L., Bryant, Robert G., Hellbaum, Richard F., Jalink, Antony Jr., Simpson, Joycelyn O., Rohrbach, Wayne W.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US08/797,553
• Publication Number:
  US 20010043027A1
• Time in Patent Office: 2,664 Days
• Field of Search: 156/160, 156/163, 156/165, 156/245, 29/253.5, 310/330, 310/331, 310/332, 310/340, 310/345, 310/367, 310/369, 310/370, 310/371, 310/311, 310/328, 264/229
• US Class Current: 310/330
• CPC Class Codes: B32B 37/144 using layers with different mechanical or chemical conditions or properties, e.g. layers with different thermal shrinkage, layers under tension during bonding constructional features for tensioning B32B38/1825
• CPC Class Codes: H10N 30/073 by fusion of metals or by adhesives
• CPC Class Codes: H10N 30/204 using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
• CPC Class Codes: H10N 30/2048 having non-planar shape
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

Claims

1. An electroactive device providing large mechanical output displacements, comprising:

a layered structure having a prestressing layer having a convex surface, and a piezoelectric layer having a concave surface, the convex surface of the prestressing layer being bonded onto the concave surface of the piezoelectric layer such that the prestressing layer is in tension and imparts a prestress on the piezoelectric layer such that the piezoelectric layer is in compression, wherein the prestressing layer and the piezoelectric layer are distinct from one another.

2. The device of claim 1, wherein the prestressing layer includes reinforcing material.

3. The device of claim 1, wherein the piezoelectric layer includes surface electrodes.

4. The device of claim 1, further comprising:

an electrode layer placed between the prestressing layer and the piezoelectric layer; and

an electrode layer placed on top of the piezoelectric layer.

5. The device of claim 1, wherein the prestressing layer is an adhesive.

6. The device of claim 1, where the piezoelectric layer is a ferroelectric material.

7. The device of claim 1, wherein the piezoelectric layer is a piezorestrictive material.

8. The device of claim 5, wherein the adhesive is a polyimide.