[Invited] Texturation of lead-free BaTiO3 based piezoelectric ceramics
Résumé
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. Among the few lead-free
materials families which can be considered for the replacement of PZT,
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 highlyoriented
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.