Texturation of lead-free BaTiO₃ based piezoelectric ceramics: [Invited]

oral invitéInternational audiencePiezoelectric ceramics have been integrated for a long time in a widerange 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 contentmust be reduced in such applications. Among the few lead-freematerials families which can be considered for the replacement of PZT,BaTiO3 appear as interesting because of its piezoelectric properties atroom temperature and capacity to be modulated by doping, even ifCurie temperature is not very high (120°C).However, ceramics are generally limited by their isotropic nature. Forthis reason, texturing process was developed in order toimprove/optimize their electromechanical properties. The aim of thepresent study is thus to obtain textured BaTiO3 based materials byusing the templated grain growth process (TGG) and to measure theirpiezoelectric properties.Doped and undoped BaTiO3 powders were prepared by classical solidstate route while BaTiO3 templates were elaborated by a molten saltsprocess. Green ceramics were then obtained by tapecasting of a slurrycontaining templates and matrix particles dispersed in theappropriated solvent. After drying, green sheet was cut, stacked,pressed and then sintered at the appropriated temperature, in order toobtain thick or thin samples. This process allowed obtaining highlyorientedmaterials (texturation degree 70% to 90%). Piezoelectricproperties were investigated, for doped and undoped samples, and fordifferent sintering parameters. Some samples appears as veryinteresting for piezoelectric applications with d33* higher than 300 pC/N, against 180 pC/N for BaTiO3 ceramics obtained by classical way