(Bi_1/2Na_1/2) TiO₃-PbTiO₃-BaTiO₃系圧電セラミックス

抄録

Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT)-based solid solution, that is, (Bi_1/2Na_1/2)_(1-x)(Pb_aBa_b)_xTiO₃(a+b=1)_??_BNPB(100x-100a/100b)_??_, are studied on their piezoelectric properties from the viewpoint of a new group of lead-free or low-lead-content piezoelectric ceramics with a rhombohedral(F_α)-tetragonal(F_β)morphotropic phase boundary(MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling.
X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi_1/2Na_1/2)TiO₃_??_BNT_??_at x=0.13_??_0.14, 0.08_??_0.09 and 0.06_??_0.07 in the case of b=0, b=0.5 and b=1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity, ε^T₃₃/ε₀, and a high electromechanical coupling factor, k₃₃, along with a high mechanical strength.