Table 1.

Important material parameters for piezoelectric ceramic, polymer, and composites. Positive and negative signs next to the properties of ceramic and polymer show the advantages and limitation, respectively of that particular parameter.

Parameter	Ceramic	Polymer	Composite
Acoustic impedance	30 (−)	4.3 (+)	10 (can be tailored)
Coupling factor	0.5–0.7 (+)	0.1–0.3 (−)	0.5–0.7
Spurious modes	many (−)	weak (+)	weak
Dielectric constant	200–5000 (+)	8–10 (−)	proportional to vol% of PZT
tan ${\delta }_m$	0.0125 (−)	0.1 (+)	0.05
tan ${\delta }_e$	0.02 (+)	0.25 (−)	0.02
Cost and Ease of fabrication	cheap (+)	expensive (−)	medium

Reprinted, with permission, from [10] © 1992 IEEE.