Abstract:

While the traditional materials of choice for piezoelectric devices over the past 60 years were lead-based perovskite ceramics, the environmental- and health-concerns, supported by governmental regulations, triggered the search for new lead-free alternatives. During the past 10 years the research output rose from 10 to 400 publications per year with China and Japan leading, Europe accounting for 10 % of the total quantity and the US only showing very select activities. The aim of this contribution is to review the global situation and present scientific challenges and advancements [1]. It is now apparent, that lead-free piezoceramics will come, but with different potency for the different applications concerned. I will specifically highlight significant recent discoveries in the field of NBT-xBT composites. NMR and simple mechanics will be used to reveal the local structure and phase composition of relaxor ferroelectrics. The design of composites allows to reduce the electric driving field [2], enhances the depolarization temperature [3] and provides a new means of making the material harder [4].
[1] J. R?del, et al?Transferring lead-free piezoceramics into application”,J. Eur. Ceram. Soc., 35, 1659-81 (2015)
[2] C. Groh, …, J. R?del, ?Relaxor/Ferroelectric Composites: A Solution in the Quest for Practically Viable Lead-Free Incipient Piezoceramics?“, Adv. Funct. Mat., 24, 356-362 (2014)
[3] J. Zhang, .., J. R?del, W. Cao and Y.-F. Chen, ?Semiconductor/relaxor 0-3 type composites without thermal depolarization in Bi0.5Na0.5TiO3 –based lead-free piezoceramics”, Nat. Comm, 6:6615  (2015)
[4] Lalitha, …, J. R?del, “Hardening of electromechanical properties in piezoceramics using a composite approach”, Appl. Phys. Let., submitted (2017)

About the Speaker:

德国国家科学与工程院院士，莱布尼兹奖获得者
Institute of Materials Science, Technische Universit?t Darmstadt

Prof. Jürgen R?del got his PhD degree from UC Berkeley in 1988, he was postdoc at NIST (USA) and TU Hamburg (Germany) before becoming full professor in Darmstadt in 1994. His current research interests include (1) Lead-free piezoceramics (2) Mechanically tuned conductivity (3) Mechanical properties of ceramics. Prof. R?del has published more than 290 papers, which have been cited more than 10 000 times. In Germany he received the highest research award for young scientists in 1992 and for senior scientists (Leibniz prize in 2009) and is Member of the German National Academy of Science and Engineering. He is “distinguished visiting professor” at Tsinghua University and guest professor at Huazhong University of Science and Technology.
 
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