Fabrication and electromechanical properties of microscale 1–3-type piezoelectric composites using (Na,K)NbO3-based Pb-free piezoceramics

Microscale 1–3-type piezoceramic/epoxy composites using Li/Ta-modified (Na,K)NbO3 (NKN-LT) lead-free piezoelectric ceramics were fabricated via a modified dice-fill method, by which the NKN-LT ceramic rods were miniaturized to a lateral width of 150 μm with an aspect ratio (height/width) higher than 3.5. The piezoelectric properties of the 1–3 composites as a function of ceramic volume fraction were measured and compared with theoretical predictions. In addition to a high electromechanical coupling coefficient (kt∼50%) and low acoustic impedances (Z∼10 Mrayls), the developed composites show a clear single thickness mode with a high resonance frequency over 3.5 MHz. The present Pb-free piezocomposites are suitable for medical imaging devices embedded in the human body.