Dielectric and piezoelectric properties of piezoceramic/polymer 1-3 composites fabricated by a modified align-and-fill technique

Piezoelectric ceramics with compositions (Pb0.94Sr0.04) (Zr0.52Ti0.48)O3 (PZT) and (Ba0.95Pb0.05) (Ti0.99Co0.01)O3 (BT) were synthesized by conventional solid state reaction technique. Three series of 1-3 composites; PZT/monothane-A70, BT/monothane-A70 and PZT/araldite-F were fabricated by a modified align-and-fill technique using the above mentioned piezoceramic compositions. Each series of the fabricated composite comprise five samples with variable ceramic contents (12-35 vol.%) and four samples with fixed ceramic volume fraction (28%) and varied ceramic aspect ratio (0.34-1.00). Dielectric, elastic and resonant characteristics of theses samples were measured. Effects of active piezoceramic composition and polymer influence on the electrical and mechanical properties of fabricated composites as a function of ceramic volume fraction were investigated. Results revealed that PZT based composites exhibit superior properties due to high piezoelectric charge coefficient (d33 ∼ 335 pC/N) and high electromechanical coupling coefficient (k33 ∼ 67%) compared to those of BT composites. It was also observed that electromechanical properties of composites are highly affected by the stiffness of the passive polymer matrix. Low stiffness (C33D ∼ 21-55 GPa) PZT/monothane-A70 composites have better acoustic impedance (Z ∼ 6-14 Mrayl), high piezoelectric charge coefficient (d33 ∼ 202-271 pC/N), high hydrostatic charge coefficient (dh ∼ 136-171 pC/N), high hydrostatic voltage coefficient (gh ∼ 33-114 × 10−3 Vm/N) and high figure of merit (FOM ∼ 4488-19,364 fm2/N) compared to PZT/araldite-F composites encompassing high stiffness (C33D ∼ 23-60 GPa). The influences of ceramic aspect ratio on the electrical properties of fabricated 1-3 composites are also discussed.