Structural, Electrical, and AC-Resistivity Studies of BNT-KN Piezoelectric Ceramics

The lead-free (1 – x) Bi0.5Na0.5TiO3 – x KNbO3 (BNT-KN; x = 0 – 0.12) composite ceramics have been synthesized by a sol-gel process. Their structure, morphology, AC conductance and dielectric response were studied systematically. The X-ray diffraction patterns of BNT-KN revealed a morphotropic phase boundary between a rhombohedral and a pseudocubic structure. The temperature-dependent dielectric response of pure BNT revealed two-phase transitions at 200 °C (TR-T or Td) and 320 °C (TC). Furthermore, the critical temperatures were found to shift to lower values with increasing KN concentration. The manifested relaxor behavior was well confirmed by a modified Curie – Weiss law. The hopping conduction mechanism in BNT-KN was characterized through AC-resistivity analysis.