Development of the properties of lead-free piezoelectric ceramics by microstructure design

Growing awareness in the World on materials that are enviromentally friendly and supporting sustainable growth, including Turkey's lead in many countries has accelerated research that takes place within the piezoelectric material for the limitation. In this thesis, it is aimed to improve the properties of NBT based lead-free oriented K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 (KBT-BT-NBT) piezoelectric ceramics with both chemical modification and crystallographic orientation approach, which exhibit high potential for many different applications. For this purpose, (1-x)(K0.5Bi0.5TiO3-BaTiO3)-xNa0.5Bi0.5TiO3 was produced with inter-step and single step production method with KBT:BT=2:1 and x=0.8. Oriented ceramics were formed, using 5, 10 and 15% by weight K0.5Bi0.5TiO3, BaTiO3, N0.5Bi0.5TiO3 templates into the matrix obtained with inter-step production, and they were shaped by tape casting technique using the templated grain growth (TGG) method. It was produced successfully after sintering 1150 ℃ and 1175 ℃ for 48 hours. For ceramics with 10% BT templated sintered at 1150 ℃ for 48 hours, the best orientation degree 74% and piezoelectric constant d33 = 188 pC/N values, while the highest polarization in ceramics with 5% BT templated under 36kV/cm electric field Pr= ~ 25 µC/cm2, 10% NBT templated ceramics under 36kV/cm electric field the highest strain ~0.3% and large signal piezoelectric coefficient d_33^*=777 pm/V values were obtained. Electrical characterization results showed that both piezoelectric coefficient and polarization capability increased by orientation according to matrix composition.