|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1998 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1997 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Recently, lead-free piezoelectric materials have been attracting attention as new materials in place of PZT materials for environments. Among of many lead-free piezoelectric materials, bismuth sodium titanate, (Bi_<1/2>Na_<1/2>)TiO_3 [BNT]-based ferroelectric ceramics will be a superior candidate. In this research, the effects of the amount of modified Bi^<3+> ions on dielectric, piezoelectric and ferroelectric properties for the BNT-based solid solution were studied by measuring on various compositions with increasing or decreasing amount of modified Bi^<3+> ions in a pseudo-three-component system, a(Bi_<1/2>Na_<1/2>)TiO_3-b KnbO_3-c l/2(Bi_2O_3. Sc_2O_3) (a +b +c =1) [KTNS (lOOa /lOOb /lOOc)] as a new group of lead-free piezoelectric ceramics. In the KTNS (lOOa/lOOb/lOOc) system, Bi^<3+> ion content can be increased by adding an amount of l/2(Bi_2O_3. Sc_2O_3) (increasing c value) and decreased by adding an amount of KnbO_3 (increasing b value) under the condition of a +b +c = 1.
Piezoelectric measurements show that the KTNS ceramics near the BNT side have a relatively high electromechanical coupling factor, k_<33> (=0.47). On particular, the amount of modified Bi^<3+> ions has an effect on k_<33>. These ceramics seem to be a candidate for lead-free piezoelectric ceramics. To attain a high electromechanical coupling factor, k, it is important to decrease the coercive field, E_c. In particular, it is clear that the amount of modified Bi^<3+> ions has an effect on E_c. When the amount of modified Bi^<3+> ions is increased, E_c becomes higher, making poling difficult and the k_<33> is the relatively low. On the other hand, when the amount of modified Bi^<3+> ions is decreased, the E_c becomes lower, making poling easy and the k_<33> is the relatively high.