Recent Developments on Piezoelectric Materials

Shujun Zhang
ISEM, Australian Institute of Innovative Materials, University of Wollongong, NSW 2500, Australia

Piezoelectric materials play an important role in electromechanical applications, such as medical imaging, structural health monitoring (SHM) and nondestructive evaluation. To improve the performance of electromechanical devices, the selection of piezoelectric material with optimized properties is a critical concern.
In this presentation, the history and applications of piezoelectric materials have been reviewed, with emphasis on recent developments of piezoelectrics, where the discussion is divided into two parts, i.e., ferroelectric and nonferroelectric materials. Special attention is focused on the temperature dependence of electromechanical properties and related mechanisms of piezoelectric materials, the potential piezoelectric materials for cryogenic and ultra-high temperature applications are also discussed.
The uniqueness of relaxor-PT crystals and nonferroelectric piezoelectric crystals are surveyed for possible electromechanical applications. Specifically, relaxor-PbTiO3 single crystals show superior piezoelectric properties, with piezoelectric coefficients of >2000pC/N and electromechanical coupling factors of >90%, far outperforming conventional ferroelectric PZTs, which greatly benefit medical ultrasound imaging [1-3]. Furthermore, good piezoelectric properties are found down to cryogenic temperatures, being on the order of 200pC/N at 20K [3]. In contrast, nonferroelectric single crystals, such as langasites, oxyborates, melilite and fresnoite crystals, possess ultrahigh electrical resistivity, being on the order of at 500oC. Though their piezoelectric coefficients fall into single digits, they are promising for high temperature sensing applications, up to 1200oC [4,5]. In addition, new development on lead free single crystals is also reviewed.

[1] S. J. Zhang and F. Li, J. Appl. Phys. 111, 031301 (2012).
[2] S. J. Zhang and T. R. Shrout, IEEE Trans. Ultrason. Ferro. Freq. Control, 57, 2138 (2010).
[3] S. J. Zhang, F. Li, X. N. Jiang, J. Kim, J. Luo and X. C. Geng, Progress in Mater. Sci. 68, 1 (2015).
[4] S. J. Zhang and F. P. Yu, J. Am. Ceram. Soc.,, 94, 3153 (2011).
[5] X. N. Jiang, K. Kim, S. J. Zhang, J. Johnson and G. Salazar, Sensors, 14, 144 (2014).

Acknowledgements: This work was supported by ONR, ONRG, NASA and NSF. Also thanks to my colleagues: Prof. T. R. Shrout; Dr. F. Li; D. J. Luo; Prof. L.Q. Chen, Dr. H. Y. Lee; Dr. F. P. Yu; Prof. X. N. Jiang and many other friends.