Domain Wall Engineering in Lead-Free Piezoelectric Materials

Grain-oriented barium titanate (BaTiO3, BT) ceramics were prepared by a templated grain growth (TGG) method using [110]-oriented BT platelike particles as a template and hydrothermal BT sphere particles with different particle sizes as a matrix. The degree of orientation along the [110] direction, F110, was measured using an X-ray diffraction (XRD) pattern by the Lotgering method. To obtain both a high density and a high F110, the preparation conditions were optimized as functions of matrix particle size, volume fraction of the template to the matrix, and sintering temperature. As for the results, BT grain-oriented ceramics with a high density of more than 96 % were successfully prepared despite various F110 values from 0 to 98 %. Scanning electron microscopy (SEM) revealed that their average grain sizes were always 75 µm despite various F110 values and there were no anisotropic microstructures. These grain-oriented BT ceramics were poled at 100 ˚C, and their piezoelectric constants d33 was measured. As for the results, the d33 values increased with increasing F110 values, and at around an F110 of 85 %, d33 reached a maximum of 788 pC/N.