[110]-oriented barium titanate (BaTiO3) ceramics were prepared by templated grain growth (TGG) method using [110]-oriented BaTiO3 platelike particles as a template and hydrothermal BaTiO3 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, BaTiO3-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 approximately 75 µm despite various F110 values and there were no anisotropic microstructures. These grain-oriented BaTiO3 ceramics were poled at 100 °C, and their piezoelectric properties were measured using a resonance–antiresonance method and a piezo d33 meter for d31 and d33 piezoelectric constants. As for the results, the d31 values were almost constant at -50 pC/N despite various F110 values, while the d33 values increased with increasing F110 values, and at around an F110 of 85%, d33 reached a maximum of 788 pC/N.
For the [111] oriented barium titanate (BaTiO 3 ) single crystals, the patterning electrode was used to induce the finer engineered domain configurations with domain size below 5 µm. The poling treatment was performed at 134.0 • C under electric fields below 6 kV/cm to inhibit the burning of the patterning electrode with photoresist. As the results, the gradient domain sizes from 3 µm (high voltage side) to 8-9 µm (ground side) were induced into the 31 resonator along thickness direction. For this resonator, the d 31 was measured at −243.2 pC/N using a resonance-antiresonance method.
We elucidated the relationship between the dielectric tunability and the electro-optic (EO) effect. A new measurement system for EO effect and dielectric permittivity (εr) was developed to investigate the accurate correlation between EO and dielectric properties of epitaxial barium strontium titanate, Ba0.5Sr0.5TiO3 (BST) thin films grown on SrTiO3 (STO) substrates. The BST films had a strained lattice with a large lattice parameter along the thickness direction. Small birefringence was induced in the as-deposited film by the alignment of the c-axis in the film plane. The tunability of dielectric permittivity calculated from the complex voltage and current with planer electrodes reached to 53.1%, and the tunability of birefringence by EO effect was 0.6%. The birefringence change from EO effect was much lower than the tunability of dielectric permittivity. Therefore, there is no strong correlation between the dielectric tunability and EO effect, and the materials with high tunability do not always exhibit high EO effect. Finally, we discussed how to obtain the materials with high EO effect considering these results.
For the [111] oriented barium titanate (BaTiO3) single crystals, the patterning electrode was applied to induce the finer engineered domain configurations with domain size of 3 2m. The poling treatment was performed at 134 °C under electric fields below 6 kV/cm to inhibit the burning of the patterning electrode with photoresist. As the results, the gradient domain sizes from 3 to 8-9 2m were induced into the 31 resonator. The d31 was measured at -243.2 pC/N, and this value was almost 70 % of the expected d31 of –337.7 pC/N for the resonator with domain size of 3 2m. This difference was originated from lower applied electric field below 6 kV/cm. However, this study was revealed that the patterning electrode was very powerful tool to induce much finer domain sizes below 5 2m.
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