Advances in development of Pb-free piezoelectric materials for transducer applications

Abstract

Pb-based ferroelectrics and piezoelectrics in the form of bulk polycrystalline, textured ceramics, single crystals, and composites, have been used in sensors, actuators, and other electromechanical devices. However, the toxicity of these materials has been a major concern around the globe for the past few decades. The report of high piezoelectric activity in the BaTiO3 (BT), (Bi0.5Na0.5)TiO3 (BNT), and (K0.5,Na0.5)NbO3 (KNN) and binary and ternary systems with other compounds have given hopes for alternatives to Pb-based materials. Recent modifications of KNN-based compositions with BaZrO3 in combination with (Bi0.5,K0.5)Hf O3 result in excellent electromechanical properties. Therefore, increased research in Pb-free materials brings hope for practical applications close to reality. In this review article, the recent developments on BT, BNT, and KNN-based soft and hard Pb-free piezoelectric compositions with a range of electromechanical properties for transducer applications will be reviewed. Several examples in the development of lead-free high-frequency ultrasound transducers will be presented.

Optimization of the calcination and two-step sintering temperatures of (K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 ceramics

“…In other words, the perfect microstructure, small grain boundaries, and high ceramic density ease the process of polarization rotation. This improves the polarization conditions of the KNLNS ceramics [28,29]. Similar results have been previously reported [30][31][32].…”

Investigation of the crystal-oriented behavior of rare earth substituted Sr2NaNb5O15 lead-free piezoelectric materials under a high magnetic field

“…Various lead-free piezoelectric materials, such as (K,Na)NbO 3 -based, (Bi,Na)TiO 3 -based, (Sr,Ca) 2 NaNb 5 O 15 (SCNN), and bismuth layer-structured ferroelectrics have been actively studied and reported to have certain advantages over PZT. [10][11][12][13][14][15][16][17][18][19][20] The c-axis crystal-oriented SCNN ceramics have good piezoelectric properties and outstanding high-power properties compared to hard-PZT, and have also demonstrated a superior performance as an ultrasonic motor using ceramics for highpower ultrasonic devices in our previous studies. 15,16,[21][22][23][24][25][26][27][28] However, there are challenges that must be addressed to achieve mass production.…”

An Emerging Era: Conformable Ultrasound Electronics

“…Clearly, in contrast to the lead‐based ceramics and crystals that have been extensively employed for various transducer configurations, the majority of research is still in the early stages and focuses on evaluating the acoustic capabilities of lead‐based ceramics utilizing single‐element probe designs. [ 88 ] For ultrahigh frequency needle transducers, KNN‐ and BNT‐based ceramics were selected, which achieved sufficient bandwidth, but were still not comparable to lead‐based piezoelectrics. There is no information reported about bulky lead‐based ceramics for cUSE, despite the fact that large lead‐based ceramics have been utilized for conformable electronics.…”