Dielectric and piezoelectric enhancement in lead-free Bi0.5Na0.5TiO3 ceramics by incorporating BaTiO3

This study presents a simple and cost-effective approach to enhance the dielectric and
piezoelectric properties of Bi₀.₅Na₀.₅TiO₃ (BNT) by incorporating BaTiO₃ (BT) via
high-energy ball milling. X-ray diffraction confirmed the formation of BNT–xBT solid
solutions and a structural transition from rhombohedral to tetragonal symmetry.
Frequency-dependent dielectric measurements showed a notable increase in relative
permittivity, reaching 1750, over twice that of undoped BNT. This enhancement is
linked to the formation of polar nanoregions (PNRs), which boost dielectric
susceptibility through localized polarization. Temperature-dependent analysis revealed
a broadened permittivity peak and diffuse phase transition, indicating disrupted long-range ferroelectric order and growing PNR activity. Polarization–electric field (P–E)
loops showed a reduction in coercive field from ~ 60 kV/cm in pure BNT to ~ 23 kV/cm
in BNT-BT modified samples, due to the coexistence of PNRs and ferroelectric
domains, facilitating polarization switching and resulting in slim hysteresis loops. The
piezoelectric coefficient d33 improved from pC/N (x = 0) to 120, 158, and 165 pC/N
for x = 0.08, 0.09, and 0.10, respectively, attributed to changes in the crystal structure
and increased domain mobility. These findings highlight the potential of BNT–xBT
obtained by high-energy ball milling as a promising lead-free piezoelectric material for
advanced electromechanical applications.