Dice-and-fill processing and characterization of microscale and high-aspect-ratio (K, Na)NbO3-based 1-3 lead-free piezoelectric composites

Piezoelectric composites with high-aspect-ratio lead-free piezoelectric microrods embedded in a polymer matrix were fabricated by applying the modified dice-and-fill method to a (K,Na)NbO3-based piezoelectric ceramic, 0.9475[Li0.02(K0.48Na0.53)0.98](Nb0.80Ta0.20)O3-0.0525AgSbO3-0.5 wt% MnO2 (abbreviated as LKNNT-AS-M) with enhanced piezoelectricity but low mechanical strength. The Pb-free LKNNT-AS-M/polymer composite specimens containing ∼10-23 vol% ceramic pillars with sectional width ∼50 μm, separation ∼55-110 μm and high aspect ratio ∼11, were prepared and investigated with an emphasis on their electrical properties. The developed composites possess a higher thickness factor kt ∼63-67%, lower planar factor kp ∼27-34% and enhanced kt/kp ratio ∼2.3. The composites also possess favorable properties which includes low electrical (tanδ ∼0.029) and mechanical (Qm ∼6) losses, low acoustic impedance Z ∼4.2-7.8 Mrayl and ∼5 times higher voltage coefficient g33 compared to LKNNT-AS-M piezoceramic. The promising results indicate that the LKNNT-AS-M/polymer composites have the potential to be used as active elements in high performance ultrasonic transducers.