Lead-Free Piezoelectric Composite With Lithium Niobate and Barium Titanate Fabricated by Interdigital Pair Bonding Technique

Abstract

Since 2003, when the European Union (E.U.) announced the restriction of hazardous substances (RoHS), multiple efforts have been made to replace lead zirconate titanate (PZT) based piezoelectric materials. However, despite these efforts, very few PZT alternatives have been found. The Lithium niobate (LN) is one such lead-free piezoelectric material often used in acoustic applications due to its high signal generation efficiency, high curie temperature, and high mechanical Q factor. However, LN is not suitable for miniaturized applications because of its low dielectric constant and high electrical impedance. In this paper, we aim to address the problem of the low-dielectric constant of LN while avoiding hazardous PZT material. We propose to utilize 1–3 composites structure with LN and barium titanate (BT), which has a high dielectric constant while controlling acoustic properties such as density, dielectric constant, sound velocity. We also developed new LN-BT modeling to design piezoelectric composite with interdigital pair bonding (IPB) technique, based on previous PZT-polymer 1–3 composite modeling. We verified that the composite components are lead-free by examining with the scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). This proposed lead-free composite with high-dielectric and lower electrical impedance is better suited for miniaturized applications.