Piezoelectrics and related devices from ceramics dispersed in polymers

A process for forming an article which comprises

• i) forming a piezoelectric composite comprising a first component that is a piezoelectric powder and a second component having three-dimensional connectivity that comprises a polymer, wherein
• (a) the first component comprises substantially spherical piezoelectric particles such that at least about 90 weight percent of the particles have diameters within 20% of the weight-average of the particle diameters, and the weight-average of the particle diameters ranges from about 30 .mu.m to about 200 .mu.m;
• (b) either (1) the polymer substantially adheres to the first component when a pellet of the polymer is fully melted and then resolidified on top of a pellet of the first component or (2) the polymer, which is formed by reaction and solidification of a fluid precursor of the polymer, substantially adheres to a pellet of the first component when said reaction and solidification is done on top of a pellet of the first component;
• (c) the dielectric loss of said polymer is less than about 0.02 at 1 kHz,
• (d) the melt index of said polymer exceeds 0.1 at a temperature within 40.degree. C. of the polymer melting temperature if said polymer has a melting temperature;
• (e) the total volume of all components of the composite other than the second component ranges from about 50 volume percent to about 74 volume percent of the composite;
• and
• (f) the elastic compliance S.sub.33 of the piezoelectric composite ranges from about 1.5.times.10.sup.-10 to about 6.0.times.10.sup.-10 m.sup.2 /N;
• and
• ii) forming a shaped article from said composite and imparting anisotropic properties to the shaped article by subjecting it to one or more treatments selected from the group consisting of uniaxially draw, uniaxial compression, biaxial draw, biaxial compression, and shear deformation.

A process of forming a composite comprising a first component that is a piezoelectric powder, a second component having three-dimensional connectivity that comprises a polymer, and a third component comprising a fibrous material or a plate-like material wherein

• (a) the first component comprises substantially spherical piezoelectric particles such that at least about 90 weight percent of the particles have diameters within 20% of the weight-average of the particle diameters, and the weight-average of the particle diameters ranges from about 30 .mu.m to about 200 .mu.m;
• (b) either (1) the polymer substantially adheres to the first component when a pellet of the polymer is fully melted and then resolidified on top of a pellet of the first component or (2) the polymer, which is formed by reaction and solidification of a fluid precursor of the polymer, substantially adheres to a pellet of the first component when said reaction and solidification is done on top of a pellet of the first component;
• (c) the dielectric loss of said polymer is less than about 0.02 at 1 kHz,
• (d) the melt index of said polymer exceeds 0.1 at a temperature within 40.degree. C. of the polymer melting temperature if said polymer has a melting temperature;
• (e) the total volume of all components of the composite other than the second component ranges from about 50 volume percent to about 74 volume percent of the composite;
• and
• (f) the elastic compliance S.sub.33 of the piezoelectric composite ranges from about 1.5.times.10.sup.-10 to about 6.0.times.10.sup.-10 m.sup.2 /N;
• the process comprising commingling the second component and third component to form an intimate mixture and then commingling the intimate mixture with the first component.

A process of forming a piezoelectric composite comprising a first component that is a piezoelectric powder and a second component having three-dimensional connectivity that comprises a polymer, wherein

• (a) the first component comprises substantially spherical piezoelectric particles such that at least about 90 weight percent of the particles have diameters within 20% of the weight-average of the particle diameters, and the weight-average of the particle diameters ranges from about 30 .mu.m to about 200 .mu.m;
• (b) either (1) the polymer substantially adheres to the first component when a pellet of the polymer is fully melted and then resolidified on top of a pellet of the first component or (2) the polymer, which is formed by reaction and solidification of a fluid precursor of the polymer, substantially adheres to a pellet of the first component when said reaction and solidification is done on top of a pellet of the first component;
• (c) the dielectric loss of said polymer is less than about 0.02 at 1 kHz,
• (d) the melt index of said polymer exceeds 0.1 at a temperature within 40.degree. C. of the polymer melting temperature if said polymer has a melting temperature;
• (e) the total volume of all components of the composite other than the second component ranges from about 50 volume percent to about 74 volume percent of the composite;
• and
• (f) the elastic compliance S.sub.33 of the piezoelectric composite ranges from about 1.5.times.10.sup.-10 to about 6.0.times.10.sup.-10 m.sup.2 /N;
• the process comprising mixing the first component and second component either as dry powders or as dry powders in combination with substantially a non-solvent for the first component and second component to form a free-flowing mixture and then forming this free-flowing mixture into a shaped composite by melting the second component.

A process of forming a piezoelectric composite comprising a first component that is a piezoelectric powder and a second component having three-dimensional connectivity that comprises a polymer, wherein

• (a) the first component comprises substantially spherical piezoelectric particles such that at least about 90 weight percent of the particles have diameters within 20% of the weight-average of the particle diameters, and the weight-average of the particle diameters ranges from about 30 .mu.m to about 200 .mu.m;
• (b) either (1) the polymer substantially adheres to the first component when a pellet of the polymer is fully melted and then resolidified on top of a pellet of the first component or (2) the polymer, which is formed by reaction and solidification of a fluid precursor of the polymer, substantially adheres to a pellet of the first component when said reaction and solidification is done on top of a pellet of the first component;
• (c) the dielectric loss of said polymer is less than about 0.02 at 1 kHz,
• (d) the melt index of said polymer exceeds 0.1 at a temperature within 40.degree. C. of the polymer melting temperature if said polymer has a melting temperature;
• (e) the total volume of all components of the composite other than the second component ranges from about 50 volume percent to about 74 volume percent of the composite;
• and
• (f) the elastic compliance S.sub.33 of the piezoelectric composite ranges from about 1.5.times.10.sup.-10 to about 6.0.times.10.sup.-10 m.sup.2 /N;
• the process comprising forming a mixture of the first component and a monomer or prepolymer, followed by reaction of said monomer or prepolymer under conditions sufficient to produce the second component.