Dielectric, ferroelectric, and piezoelectric properties of Nb-substituted Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics

The effects of niobium substitution on the crystal structure and on the ferroelectric and piezoelectric properties of Bi1/2(Na0.82K0.18)1/2(Ti)O3 (BNKT) ceramics have been investigated. X-ray diffraction analyses revealed that Nb-substitution induced a phase transition from the coexistence of rhombohedral-tetragonal symmetry to pseudocubic symmetry. Accordingly, the electric-fieldinduced polarization and strain hysteresis loops indicated that Nb substitution significantly disrupted the ferroelectric order of BNKT ceramics, leading to degradations in the remnant polarization, coercive field, and piezoelectric coefficient d 33. However, the destabilization of the ferroelectric order was accompanied by a significant enhancement in the electric-field-induced strain (EFIS), which peaked at x = 0.03 with a value of 0.47%. The abnormal enhancement in the EFIS could be attributed to a phase transition from a non-polar to a polar phase under an applied electric field.