Abstract For the [111] oriented barium titanate (BaTiO3) single crystals, the patterning electrode was used to induce the finer engineered domain configurations with domain size below 5 μ m. 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 μ m (ground side) were induced into the 31 resonator along thickness direction. For this resonator, the d31 was measured at −243.2 pC/N using a resonance-antiresonance method. Keywords: Barium titanatedomain engineeringdomain wall Acknowledgments We would like to thank Mr. O. Nakao of Fujikura Ltd. for preparing the TSSG-grown BaTiO3 single crystals with excellent chemical quality. This study was partially supported by (1) a Grant-in-Aid for Scientific Research (16656201) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan, (2) the Japan Securities Scholarship Foundation, (3) the Toray Science Foundation, (4) the Kurata Memorial Hitachi Science and Technology Foundation, (5) the Electro-Mechanic Technology Advanced Foundation, (6) the Tokuyama Science Foundation and (7) the Yazaki Memorial Foundation for Science and Technology.
To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.
For [111] poled barium titanate (BaTiO3) single crystals, piezoelectric properties increased with decreasing domain sizes. To explain the phenomenon, the multidomain crystals were regarded as composite of (a) a distorted 90° domain wall region with ultrahigh piezoelectric property and (b) a normal tetragonal domain region. This model suggested that the d 31 of the lead-free piezoelectric crystals with domain sizes below 1 μ m can be over 1,000 pC/N. Thus, to induce the finer engineered domain configurations, a patterning electrode was used. As the results, the domain size of 3 μm was successfully induced, and the d31 was obtained at −243.2 pC/N.
Silver lithium niobate (Ag 1-x Li x NbO 3 ALN) single crystals with Li contents of 10 and 12.5 mol% were successfully grown by a slow cooling method. The high-energy X-ray diffraction measurement revealed that the crystal structures of both ALN10 and ALN12.5 were assigned to the coexistence between orthorhombic Pc2 1 b and rhombohedral R3m phases. Their piezoelectric properties were investigated as a function of crystallographic direction and Li content.
For potassium niobate (KNbO3) single crystal, the 31 resonators with the highest piezoelectric constant d31 were designed using transformation of axis. We confirmed that the engineered domain configurations with maximum d31 of –55.1 pC/N was caused by a combination between two polarization with polar directions along [101]c and [-101]c directions. Moreover, if there are larger piezoelectric constants from domain wall region, we can expect the much higher piezoelectric properties. To induce the above domain configuration, a new poling method using patterning electrode was investigated. In this study, the two methods on the basis of temperature-induced phase transition at 207 °C and electric-field-induced phase transition at room temperature were investigated.
The phase transition behaviors of the [111] oriented barium titanate (BaTi0 3 ) single crystals were investigated as functions of temperature, uniaxial stress and electric fields.For the phase transition by temperature, with decreasing temperature above Tc, the paraelectric phase changed to the intermediate phase with superparaelectric state, and finally change to the ferroelectric phase with randomly oriented spontaneous polarizations.Moreover, it was also found that the phase transition by uniaxial stress field above Tc was almost similar one by temperature.On the other hand, for the phase transition by electric field above Tc, with increasing electric field, the paraelectric phase changed to the intermediate phase, and finally changed to the ferroelectric phase with the oriented polar direction.These results suggested that above Tc, combination between uniaxial stress and electric fields might be effective for a poling treatment of BaTi0 3 crystals.Thus, in this study, a new poling method for the BaTi0 3 crystals was proposed using control of temperature, uniaxial stress and electric fields.
