Effect of Ce on structural and dielectric properties of lead-free (Bi0.5Na0.5)TiO3 ceramics

The structural, microstructural and dielectric properties of the Ce doped Bi0.5Na0.5TiO3 (BNTC) lead-free piezoelectric ceramics prepared by a conventional solid state reaction process have been investigated. Rietveld refinement of the BNTC ceramics shown that the volume of the unit cell increased with the concentration of Ce up to x = 0.015 and decreases further with the excess Ce doping (≥ x = 0.025). The average grain size of the BNTC ceramics found to be increased linearly up to x = 0.015 and higher concentration of Ce inhibited the grain growth. The dielectric response of the Ce doped BNT ceramics improved significantly and the optimum dielectric properties (εr = 672 and tan δ = 0.206 at 1 MHz) were obtained for the composition of x = 0.025. For the low concentration of x, the Ce3+ was substituted in Ti4+ site, which enhanced the diffuseness coefficient (γ = 1.83). Conversely, the γ value was found to be decreased when x ≥ 0.025, which is due to the substitution of Ce3+ in Na+ site instead of Ti4+ site and weakens the relaxor behavior. The temperature dependent of AC-conductivity of BNTC ceramics was analyzed using Arrhenius's law and the variable range hopping (VRH) model and the corresponding density of states (N(EF)), hopping length (RH), and hopping energies (WH) were calculated. The obtained results indicate that BNTC ceramics are suitable for promising industrial high performance piezoelectric applications.