1. 2 T. R. Shrout and S. J. Zhang , “Lead-Free Piezoelectric Ceramics: Alternatives for PZT,” J. Electroceram., 19, 111-24 (2007).
2. 3 Y. Saito , H. Takao , T. Tani , T. Nonoyama , K. Takatori , T. Homma , T. Nagaya , and M. Nakamura , “Lead-Free Piezoceramics,” Nature, 432, 84-7 (2004).
3. 4 Y. Saito and H. Takao , “High Performance Lead-Free Piezoelectric Ceramics in the (K,Na)NbO3-LiTaO3 Solid Solution System,” Ferroelectrics, 338, 17-32 (2006).
4. 5 M. Kosec and D. Kolar , “On Activated Sintering and Electrical Properties of NaKNbO3,” Mater. Res. Bull., 10, 335-40 (1975).