Piezoelectric composite and method of forming same

Abstract

A piezoelectric composite for use in an ultrasonic transducer and a method of forming the same is provided. The composite has a piezoelectric ceramic component and a hydrophobic polymer component arranged to form a 1-3, 2-2, or 3-3 composite type. In one embodiment, the hydrophobic polymer is selected to polymerize at a moderate temperature.

What is claimed is: 
     
         1 . A piezoelectric composite comprising a plurality of piezoelectric ceramic components and a hydrophobic polymer component, wherein the plurality of piezoelectric ceramic components and the hydrophobic polymer component are arranged to form a composite type selected from the group consisting of a 1-3 composite type, a 2-2 composite type, and a 3-3 composite type. 
     
     
         2 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer component is a polymerization product of a reaction mixture comprising a siloxane epoxide monomer and a photoacid generator. 
     
     
         3 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer is a polymerization product of a reaction mixture comprising an epoxide monomer and photoacid generator. 
     
     
         4 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer is a polymerization product of a reaction mixture comprising a neat epoxide monomer and photoacid generator. 
     
     
         5 . The piezoelectric composite as recited in  claim 4 , wherein the photoacid generator is present in the reaction mixture at a concentration between 0.25% by weight and 3% by weight. 
     
     
         6 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer is a polymerization product of a reaction mixture comprising an epoxide monomer, photoacid generator, and an epoxide toughening monomer that is different than the epoxide monomer. 
     
     
         7 . The piezoelectric composite as recited in  claim 6 , wherein the epoxide toughening monomer comprises a plurality of dimethylsiloxane moieties and at least one epoxide moiety. 
     
     
         8 . The piezoelectric composite as recited in  claim 6 , wherein the epoxide toughening monomer is present in the reaction mixture at a concentration between 0.25% by weight and 40% by weight. 
     
     
         9 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer is a polymerization product of a reaction mixture comprising an epoxide monomer, photoacid generator, an epoxide toughening monomer that is different than the epoxide monomer, and an adhesion promoter. 
     
     
         10 . The piezoelectric composite as recited in  claim 9 , wherein the adhesion promoter is present in the reaction mixture at a concentration between 0.25% by weight and 6% by weight. 
     
     
         11 . The piezoelectric composite as recited in  claim 1 , wherein the hydrophobic polymer component has less than a 4% change in mass when tested according to ASTM Standard D 570-98(2010)e1. 
     
     
         12 . The piezoelectric composite as recited in  claim 1 , wherein the piezoelectric composite type is a 1-3 composite type. 
     
     
         13 . The piezoelectric composite as recited in  claim 12 , wherein the plurality of piezoelectric ceramic components are posts having a length-to-width aspect ratio of at least 2.5 to 1. 
     
     
         14 . The piezoelectric composite as recited in  claim 1 , wherein the plurality of piezoelectric ceramic components and the hydrophobic polymer component are arranged such that the plurality of piezoelectric ceramic components occupies between 20% and 80% by volume of the piezoelectric composite. 
     
     
         15 . The piezoelectric composite as recited in  claim 14 , wherein the plurality of piezoelectric ceramic components and the hydrophobic polymer component are arranged such that the hydrophobic polymer component occupies between 20% and 80% by volume of the piezoelectric composite. 
     
     
         16 . A method of forming a piezoelectric composite, the method comprising steps of:
 dicing a ceramic to form a plurality of piezoelectric ceramic components, wherein the step of dicing forms grooves between each piezoelectric ceramic component while leaving each piezoelectric ceramic component monolithically joined to a back plate;   filling the grooves with a reaction mixture comprising a photoacid generator and an epoxide monomer selected to provide a hydrophobic polymer component;   initiating a polymerization reaction in the reaction mixture; and   permitting the polymerization reaction to cure to form the hydrophobic polymer component within the grooves, thereby forming a piezoelectric composite.   
     
     
         17 . The method as recited in  claim 16 , wherein the step of initiating and the step of permitting are both performed between 20° C. and 30° C. 
     
     
         18 . The method as recited in  claim 16 , further comprising grinding a top portion of the piezoelectric composite. 
     
     
         19 . The method as recited in  claim 16 , wherein the step of initiating the polymerization reaction comprises exposing the reaction mixture to ultraviolet light. 
     
     
         20 . An ultrasonic transducer comprising:
 a piezoelectric composite comprising a plurality of piezoelectric ceramic components and a hydrophobic polymer component, wherein the plurality of piezoelectric ceramic components and the hydrophobic polymer component are arranged to form a composite type selected from the group consisting of a 1-3 composite type, a 2-2 composite type and a 3-3 composite type;   a printed circuit board providing an electrical connection between the plurality of piezoelectric ceramic components and a cable;   a substrate contacting terminal ends of the plurality of piezoelectric ceramic components to provide an acoustic energy transmission window; and   a case, joined to the substrate to encase the piezoelectric composite and the printed circuit board, wherein the cable provides an electrical connection outside of the case.