CeraNova Corporation

Infrared Transparent Ceramics

Active Composite Fibers for Smart Structures

Piezoceramics

Piezoelectricity is a property of certain crystalline materials.  When a mechanical force is applied to these materials an electric field proportional to the magnitude of the stress is produced.  Conversely, when an electric field is applied to a piezoelectric, a mechanical stress develops that may produce a shape change.  

There are several piezoelectric materials that are used to make electromechanical sensors and actuators.  Some examples of practical piezo materials are barium titanate, lithium niobate, polyvinyledene difluoride (PVDF), and lead zirconate titanate (PZT).  There are several different formulations of the PZT compound, each with different electromechanical properties.

The underlying mechanism behind piezoelectricity is an asymmetry in the unit cell of the materials.  Piezo materials contain domains, i.e., regions which possess a spontaneous electric polarization.  When subjected to an external electric field, these domains can reverse their orientation and this behavior is the defining characteristic of piezoelectrics.  This phenomenon exhibits itself through a saturating type hysteresis curve that can be generated by plotting the measured electric charge vs. field.

Bulk piezo materials are shaped and processed using a number of different techniques, including injection molding, tape casting, and extrusion.  When bulk piezoelectric materials are first prepared, the crystalline grains and domains are randomly oriented.  A poling process is required to establish a dominant domain alignment and thus maximize the energy conversion efficiency.  Poling is usually performed by subjecting the materials to a high electric field (~10 kV/cm) at slightly elevated temperatures (~100 °C) for a short period of time.

At CeraNova, we have developed proprietary methods of extruding and sintering fine diameter piezoceramic fibers.  Our monofilament fibers and ribbons are manufactured to tight dimensional tolerances and have excellent electrical properties.  These fibers range in size from 100 µm to 600 µm in diameter or thickness.