TY - JOUR AB - (K,Na)NbO3 ceramics have attracted much attention as lead-free piezoelectric materials with high piezoelectric properties. High-quality (K,Na)NbO3 ceramics can be sintered using KNbO3 and NaNbO3 powders synthesized by a hydrothermal method. In this study, to enhance the quality factor of the ceramics, high-power ultrasonic irradiation was employed during the hydrothermal method, which led to a reduction in the particle size of the resultant powders. AU - Isobe, G. AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9878 IS - 2 JF - Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on KW - Q-factor KW - ceramics KW - crystal growth from solution KW - particle size KW - piezoelectric materials KW - potassium compounds KW - powders KW - sintering KW - sodium compounds KW - ultrasonic effects KW - (K0.48Na0.52)NbO3 KW - KNbO3 powders KW - NaNbO3 powders KW - high-power ultrasonic irradiation KW - lead-free piezoelectric materials KW - lead-free piezoelectric powders KW - particle size reduction KW - piezoelectric properties KW - quality factor KW - sintered (K0.48Na0.52)NbO3 ceramics KW - sintering KW - ultrasonic-assisted hydrothermal method KW - Acoustics KW - Ceramics KW - Lead KW - Piezoelectric materials KW - Powders KW - Radiation effects KW - Transducers SN - 0885-3010 TI - Synthesis of lead-free piezoelectric powders by ultrasonic-assisted hydrothermal method and properties of sintered (K0.48Na0.52)NBO3 ceramics VL - 61 ER - TY - CONF AB - A hydrothermal method utilizes a crystallization process in the solution so that the pure and high-quality powders can be realized. Sintering from the hydrothermal KNbO3 and NaNbO3 powders, a high-dense lead-free piezoelectric (K,Na)NbO3 ceramics could be obtained (density: 98.8\%). Concerning about the g33 constant, high value as large as commercial PZT ceramics was measured. Therefore, the hydrothermal (K,Na)NbO3 ceramics is usable for the sensors and the energy harvesting devices. To demonstrate the (K,Na)NbO3 ceramics, a hydrophone sensor was fabricated and evaluated. AU - Maeda, Takafumi AU - Bornmann, Peter AU - Hemsel, Tobias AU - Morita, Takeshi ID - 9788 KW - crystallisation KW - hydrophones KW - piezoceramics KW - potassium compounds KW - powder technology KW - powders KW - sensors KW - sintering KW - sodium compounds KW - (K0.48Na0.52)NbO3 KW - KNbO3 powder KW - NaNbO3 powder KW - crystallization KW - energy harvesting devices KW - g33 constant KW - hydrophone sensor KW - hydrothermal lead-free (K0.48Na0.52)NbO3 ceramics KW - hydrothermal method KW - piezoelectric applications KW - sintering KW - Materials KW - Transducers SN - 1948-5719 T2 - Ultrasonics Symposium (IUS), 2012 IEEE International TI - Piezoelectric applications of hydrothermal lead-free (K0.48Na0.52)NbO3 ceramics ER - TY - JOUR AB - The hydrothermal method enables the production of high-quality piezoelectric materials. In this study, we propose to irradiate the reaction solutions with ultrasonic power during the hydrothermal method to obtain a shorter reaction time and a smooth film surface. A high-pressure reaction container for the ultrasonic transducer was newly developed, and the ultrasonically-assisted hydrothermal method was examined by using this container. The effect of ultrasonic assist on the synthesis of lead-zirconate-titanate (PZT) thin films and (K,Na)NbO$_{3}$ powders was verified. Thicker PZT film, thickness around 10 ${\mu}$m, could be obtained in one process, and (K,Na)NbO$_{3}$ powder was synthesized in half the previous reaction time. AU - Ageba, Ryo AU - Kadota, Yoichi AU - Maeda, Takafumi AU - Takiguchi, Norihito AU - Morita, Takeshi AU - Ishikawa, Mutsuo AU - Bornmann, Peter AU - Hemsel, Tobias ID - 9743 IS - 4 JF - Journal of Korean Physical Society KW - Hydrothermal method KW - High-power ultrasonic KW - PZT thin film KW - Lead-free piezoelectric materials SN - 1948-5719 TI - Ultrasonically-assisted Hydrothermal Method for Ferroelectric Material Synthesis VL - 57 ER - TY - JOUR AB - Direct ultrasound irradiation is advantageous to increase the efficiency of the hydrothermal method which can be used for the production of piezoelectric thin films and lead free piezoelectric ceramics. To apply ultrasound directly to the process transducer prototypes were developed regarding the boundary conditions of the hydrothermal method. LiNbO$_{3}$ and PIC 181 were proven as feasible materials for high temperature resistant transducers ($\geq 200^\circ C$). Resistance of the transducers horn against the corrosive mineralizer was achieved by using Hastelloy C-22. The efficiency of the ultrasound assisted hydrothermal method depends on the generated sound field. Impedance and sound field measurements have shown that the sound field depends on the filling level and the position and design of the transducer. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Littmann, Walter AU - Ageba, Ryo AU - Kadota, Yoishi AU - Morita, Takeshi ID - 9744 IS - 4 JF - Journal of Korean Physical Society KW - High-temperature transducer KW - Hydrothermal method KW - Lithium-niobate transducer SN - 1948-5719 TI - Ultrasonic Transducer for the Hydrothermal Method VL - 57 ER - TY - JOUR AB - As a lead-free piezoelectric ceramics, (K,Na)NbO$_{3}$ is a promising material because of its good piezoelectric properties. In this study, (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics were synthesized from a KNbO$_{3}$ and NaNbO$_{3}$ mixture powder prepared by the hydrothermal reaction. The hydrothermal reaction enables the production of high quality powder for the ceramics fabrication process. To obtain (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics, these two powders KNbO$_{3}$ and NaNbO$_{3}$ were mixed and then sintered together. X-Ray diffraction analysis revealed that the solid solution ceramics (K$_{1-x}$Na$_{x}$)NbO$_{3}$ was produced by the sintering process. The K/Na ratio in (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics was optimized for the best piezoelectric properties. The optimized forms was (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$, which showed the following piezoelectric properties; k$_{33}$=0.56, d$_{33}$=114pC/N. In addition, the ferroelectric properties, P$_{r}$=7.72mC/cm$^{2}$, E$_{c}$=857V/mm, and the Curie temperature T$_{c}$=420$_{o}$C were also measured. AU - Maeda, Takafumi AU - Takiguchi, Norihito AU - Morita, Takeshi AU - Ishikawa, Mutsuo AU - Hemsel, Tobias ID - 9758 IS - 4 JF - Journal of Korean Physical Society KW - Lead-free piezoelectric material KW - KNN KW - Hydrothermal method SN - 1948-5719 TI - Hydrothermal (K1-xNax)NbO3 Lead-free Piezoelectric Ceramics VL - 57 ER -