Texturation of lead-free BaTiO3 based piezoelectric ceramics

Piezoelectric ceramics have been integrated for a long time in a wide range of devices, particularly in ultrasonic applications (sonar systems, medical imaging…) and most of them use Pb(Zr,Ti)O3 (PZT) materials. However,... [ view full abstract ]

Piezoelectric ceramics have been integrated for a long time in a wide range of devices, particularly in ultrasonic applications (sonar systems, medical imaging…) and most of them use Pb(Zr,Ti)O₃ (PZT) materials. However, due to health care and environmental problems, lead content must be reduced in such applications [1]. Among the few lead-free materials families which can be considered for the replacement of PZT [2, 3], BaTiO₃ appear as interesting because of its piezoelectric properties at room temperature and capacity to be modulated by doping, even if Curie temperature is not very high (120 °C).

However, ceramics are generally limited by their isotropic nature. For this reason, texturing process was developed in order to improve/optimize their electromechanical properties. The aim of the present study is thus to obtain textured BaTiO₃ based materials by using the templated grain growth process (TGG) and to measure their piezoelectric properties.

Doped and undoped BaTiO₃ powders were prepared by classical solid state route while BaTiO₃ templates were elaborated by a molten salts process. Green ceramics were then obtained by tapecasting of a slurry containing templates and matrix particles dispersed in the appropriated solvent. After drying, green sheet was cut, stacked, pressed and then sintered at the appropriated temperature, in order to obtain thick or thin samples. This process allowed obtaining highly-oriented materials (texturation degree 70% to 90%). Piezoelectric properties were investigated, for doped and undoped samples, and for different sintering parameters. Some samples appears as very interesting for piezoelectric applications with d33* higher than 300 pC/N, against 180 pC/N for BaTiO₃ ceramics obtained by classical way.

[1] Directive 2002/95/EC, Official Journal of the European Union,13.2.2003

[2] J. Rodel, W. Jo, T.P. Seidert, E-M. Anton, T. Granzow, D. Damjanovic, J. Am. Ceram. Soc. 92 (2009), p. 1153-1177 

[3] P.K. Panda, J. Mater. Sci. 44 (2009), p. 5049-5062