Isobe, G., et al. “Synthesis of Lead-Free Piezoelectric Powders by Ultrasonic-Assisted Hydrothermal Method and Properties of Sintered (K0.48N.52)NBO3 Ceramics.”10.1109/TUFFC.2014.6722608__Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions On, vol. 61, no. 2, 2014, pp. 225–30, doi:10.1109/TUFFC.2014.6722608.

Maeda, Takafumi, et al. “Piezoelectric Applications of Hydrothermal Lead-Free (K0.48N.52)NbO3 Ceramics.”10.1109/ULTSYM.2012.0048__Ultrasonics Symposium (IUS), 2012 IEEE International, 2012, pp. 194–95, doi:10.1109/ULTSYM.2012.0048.

Ageba, Ryo, et al. “Ultrasonically-Assisted Hydrothermal Method for Ferroelectric Material Synthesis.”10.3938/jkps.57.918__Journal of Korean Physical Society, vol. 57, no. 4, 2010, pp. 918–23, doi:10.3938/jkps.57.918.

Bornmann, Peter, et al. “Ultrasonic Transducer for the Hydrothermal Method.”10.3938/jkps.57.1122__Journal of Korean Physical Society, vol. 57, no. 4, 2010, p. 1122, doi:10.3938/jkps.57.1122.

Maeda, Takafumi, et al. “Hydrothermal (K1-XNax)NbO3 Lead-Free Piezoelectric Ceramics.”10.3938/jkps.57.924__Journal of Korean Physical Society, vol. 57, no. 4, 2010, pp. 924–28, doi:10.3938/jkps.57.924.