Study of phase, dielectric and electrical properties of (Bi_0.5Na_0.5)_0.935Ba_0.065Ti_1−xMg_xO₃ ceramics

Lead-free piezoelectric Mg^{2 +} doped Bi_0.5Na_0.50.935Ba_0.065Ti_1−xMg_xO₃(0 ≤ x ≤ 0.03) ceramics were synthesized via solid-state route calcined at 850 °C and sintered at 1160°C. The phase, microstructure, and dielectric properties of BNBT were investigated by X-ray diffraction, scanning electron microscopy and impedance analyzer. X-ray diffraction (XRD) spectra show an increase in the peak intensities when doped with Mg²⁺ in the samples. XRD furthermore reveals the samples crystallizes in cubic crystal structure for 0 ≤ x ≤ 0.03 having space group Pm3m and lattice constant increased from 3.85631 Å to 3.87629 Å. Scanning electron microscopy shows a dense microstructure with particle size varies from 0.92µm to 0.59 µm with Mg²⁺ concentration. The dielectric constant (ε_r)increases by increasing the dopant concentration. The maximum dielectric constant and dielectric loss determined above the Curie temperature (CT) areε_r=4910 and1.5for the composition x = 0.03 at CT 310 °C and frequency 10 kHz. Further, below the CT a secondary phase occurs at 460 °C due to the thermal polarization and charge accumulation at the grain boundaries which increases the dielectric constant.