Abstract
Lead-free (1-y)(Bi0.5Na0.49-xKxAg0.01)TiO3–yBaTiO3 (x=0 to 0.1, y=0 to 0.04) [abbreviated as BNKAT-BT-100x/100y] piezoelectric ceramics were fabricated using various amounts of K and Ba substitutions, and their piezoelectric and dielectric properties were investigated. The crystal structure significantly changed with the amount of K substitution. The BNKAT-BT-5/2 specimens exhibited a pseudocubic structure, while the BNKAT-BT-10/2 specimens exhibited a tetragonal structure and provided a larger electrostrain constant (d33*) than BNKAT-BT-0/2 specimens, which exhibited a rhombohedral structure. The addition of La2O3/MnO to BNKAT-BT specimens affected the crystal structure and electrical properties. La2O3/MnO-added BNKAT-BT-10/100y (0.02≦y≦0.03) specimens with a pseudocubic structure exhibited P–E hysteresis loops different from those that are characteristic of ferroelectric, and provided a peculiar field-induced strain without the residual strain in the butterfly curve and a very large strain constant (d33*) of 415 pm/V. This may be associated with the field-forced phase transition from the paraelectric phase to the ferroelectric phase.