Morphotropic phase boundary and electric properties in (1 -x)Bi_(0.5)Na_(0.5)TiO_(3-x)BiCoO_3 lead-free piezoelectric ceramics

摘要

Lead-free (1-x)Bi_(0.5)Na_(0.5)TiO_3-xBiCoO_3(x = 0, 0.015, 0.025, 0.03, 0.035, 0.04, and 0.06) piezoelectric ceramics have been synthesized and their structure and electric properties have been investigated systemically. The rhombohedral-tetragonal morphotropic phase boundary (MPB) locates near x = 0.025-0.035. For the ceramics with x - 0.025, the saturated polarization (P_s), remnant polarization (P_r), coercive field (E_c), strain(S), piezoelectric constant (d_(33)), and thickness electromechanical coupling factor (k_t) are 40.6μC/cm~2, 35.4μC/cm~2, 5.25kV/mm, 0.11%, 107pC/N, and 0.45, respectively. The low temperature humps of relative dielectric constant, which is indicative of T_(r-t), are becoming inconspicuous gradually with the increasing x and almost disappear at x= 0.04. The depolarization temperature T_d decreases first and then increases with the increasing x. Our results may be helpful for further work on Bi_(0.5)Na_(0.5)TiO_3-based lead-free piezoelectric ceramics.