Piezoelectric ceramics with high d33 constants and their application to film speakers

Abstract

A multilayer piezoelectric material was fabricated using piezoelectric materials with low-temperature sintering capabilities and high piezoelectric coefficients to develop a functionally superior piezoelectric speaker with a large-displacement deformation. A soft relaxor was utilized to prepare the component materials,( with the optimized) composition of the investigated piezoelectric ceramics represented by 0.2Pb (Zn0.8 Ni0.2 ) 1 Nb 2 O3 − 0.8Pb(Zr0.5 Ti0.5 )O3 . Li2CO3 was added to 3 3 assist the low-temperature sintering conducted at 875◦C, which yielded a multilayer piezoelectric material with superior properties (d33 = 500 pC N−1, kp = 0.63, g33 = 44 mV N−1 ). A multilayer piezoelectric actuator with a single-layer thickness of ~40 µm and dimensions of 12 × 16 mm2 was fabricated by tape casting the prepared green sheets. Finite element analysis revealed that the use of a PEEK film and a smaller silicone–rubber film as a composite in the diaphragm realized optimal frequency-response characteristics; the vibrations generated by the piezoelectric element were amplified. The optimal structure obtained via simulations was applied to fabricate an actual piezoelectric speaker with dimensions of 20 × 24 × 1 mm3 . The actual measurements exhibited a sound pressure level of ~75 dB and a total harmonic distortion ≤15% in the audible frequency range (250–20,000 Hz) at an applied voltage of 5 Vp .