USA As Represented by Secretary of the Navy

Mark Chase

Manfred Kahn

A piezoelectric ceramic-polymer composite is made of a substantially two-dimensional polymer matrix and a monolayer of sintered piezoelectric ceramic granules dispersed throughout the matrix so that each granule has an upper portion protruding from one side of the matrix and a lower portion protruding from the opposite side of the matrix. The composite is formed by partially embedding a monolayer of sintered piezoelectric ceramic granules in a pliable material, then partially covering the granules with a polymer resin, curing the resin to form a matrix and removing the pliable material. A transducer is formed by flattening the upper and lower portions of the granules to form coplanar top and bottom surfaces parallel to, but not coplanar with the surface of the matrix, then electroding the granule surfaces, attaching top and bottom cover plates, and sealing the transducer around the edges.

Tranducing composite of sintered piezoelectric ceramic granules in a polymer matrix

Method of making a transducing composite of sintered piezoelectric

The process for making a porous mass containing dense aggregates or granu includes the steps of mixing powder with more than 10% by weight of a binder to form agglomerated powder, heating the agglomerated powder to remove the binder and to grow crystallites in the powder to an average diameter exceeding 5 microns to form a porous mass containing the dense aggregates, and cooling the porous mass. The porous mass is broken up, if it is cohesive, into the aggregates containing the crystallites and the aggregates can be used to make an article, such as a transducer. The transducer is essentially a thick film and its thickness is that of the ceramic aggregates of granules. The electrodes connect to the top and to the bottom of the aggragates. As a result, the transducer material operates in the 1-3 mode.

Making large porous aggregates

Making aggregates and articles made therefrom

A piezoelectric ceramic hydrostatic sound sensor or transducer having high ensitivity to hydrostatic pressure is made by placing a flat plastic disc between two flat layers of green ceramic material, compressing and fusing the layers, heating to a first temperature at which the plastic decomposes, leaving a flat void in the ceramic, and heating to a second temperature at which the ceramic sinters. The transducer is provided with electrodes on its top and bottom surfaces. In a further improvement, ceramic particles are provided which are entrapped in the void; they render the sound sensor sensitive to inertial forces. In yet another improvement, the inside walls of the void are coated with a conductive noble metal connected to a terminal wire, whereby an additional electrode is provided for sensing the electromechanical response of the transducer.

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Laurel, MD, United States of America

Mark Chase