Synthetic Single Crystal Research Center, Shanghai Institute of Ceramics
Key Laboratory of Transparent Opto-functional Inorganic Materials, CAS
Lead-free piezoceramics: From basic science to application
Speaker：Prof. Jürgen Rödel
Institute of Materials Science, Technische Universität Darmstadt
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. In addition, a number of companies invested large sums into research and they aim at solid financial return. Some of them produced material reproducibly in 100 kg batches and select areas were identified, where lead-free piezoceramics have an advantage to lead-containing piezoceramics. As a result, the first products started to appear at the market place.
The aim of this contribution is to review the global situation and present scientific challenges and advancements . It is now apparent, that lead-free piezoceramics will come, but with different potency for the different applications concerned.
In the interest of time, I will focus on NBT-xBT piezoceramics. I will introduce their properties and will discuss recent work on the local structure. After a discussion of orientation-dependent properties in single crystals, I will specifically highlight significant recent discoveries in the field of NBT-BT composites. They allow to reduce the electric driving field [3, 4], enhance the depolarization temperature  and provide a new means of making the material harder .
In the end I provide examples for application relevant work on electrical fatigue and on fracture toughness of NBT-xBT piezoceramics.
Jürgen Rödel, Wook Jo, Klaus Seifert, Eva-Maria Anton, Torsten Granzow and Dragan Damjanovic, “Perspective on the Development of Lead-Free Piezoceramics”, J. Amer. Ceram. Soc., 92  1153-1177 (2009)
J. Rödel, K.G. Webber, R. Dittmer, W. Jo, M. Kimura and D. Damjanovic, „Transferring lead-free piezoceramics into application”, J. Eur. Ceram. Soc., 35, 1659-81 (2015)
C. Groh, D.J. Franzbach, W. Jo, K.G. Webber, J. Kling, L.A. Schmitt, H.-J. Kleebe, S.-J. Jeong, J.-S. Lee and J. Rödel, „Relaxor/Ferroelectric Composites: A Solution in the Quest for Practically Viable Lead-Free Incipient Piezoceramics?“, Adv. Funct. Mat., 24, 356-362 (2014)
M. Acosta, W. Jo and J. Rödel, „Temperature- and Frequency-dependent properties of the 0.75Bi1/2Na1/2TiO3 -0.25SrTiO3 lead-free incipient piezoceramic”, J. Amer. Ceram. Soc., 97  1937-43 (2014)
J. Zhang, Z. Pan, F.-F. Guo, W.-C. Liu, H. Ning, Y.B. Chen, M.-H. Lu, B. Yang, J. Chen, S.-T. Zhang, X. Xing, J. Rödel, 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)
Lalitha, K.V., L. Riemer, J. Koruza and J. Rödel, “Hardening of electromechanical properties in piezoceramics using a composite approach”, Appl. Phys. Let., submitted (2017)
Prof. Jürgen Rödel 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.
Jürgen Rödel has published more than 280 papers, which have been cited more than 10 000 times. In Germany he received the highest research award for young scientists (Maier-Leibnitz prize 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.