Biocompatible Aurivillius-like layered ferroelectric BaIn2Ta2O9

A biocompatible Aurivillius-like layered ferroelectric that was designed by first-principles analysis and its thin film fabricated using radio frequency magnetron sputtering has been utilized for sensors of biomedical microelectromechanical systems. Aurivillius ferroelectrics have superior characteristics such as ferroelectric anisotropies and high Curie temperatures, and are widely used for sensors and memories. However, they contain the bio-toxic element, bismuth. In this study, we designed and fabricated a new biocompatible Aurivillius-like ferroelectric. SrBi2Ta2O9 was subjected to first-principles calculation for validation. Lattice parameters of SrBi2Ta2O9 in each phase and the spontaneous polarization value were in good agreement with the experimental reports. Subsequently, the prediction of Aurivillius-like materials and generation of its thin films were performed. During the design of the new molecule, 37 candidates were obtained by including constraint conditions such as the tolerance factor. We carried out the first-principles calculations for the structure optimization, determination of the band gap (for insulation), the soft mode (for ferroelectric phase transition), and the ferroelectric properties. The spontaneous polarization of BaIn2Ta2O9 was calculated as 7.95 nC/cm2. Next, a BaIn2Ta2O9 thin film was generated. Through the experimental design procedure using an L27 orthogonal array, we determined the sputtering conditions. Introducing the post-annealing process, the polarization-electric field hysteresis loop was obtained and its remnant polarization was calculated to be 15 nC/cm2. The x-ray diffraction pattern predicted the crystal structure of SrBi2Ta2O9-type materials. These results show the possible formation of the biocompatible Aurivillius-like ferroelectric material, BaIn2Ta2O9.