Effect of Ce on structural and dielectric properties of lead-free (Bi 0.5 Na 0.5 )TiO 3 ceramics

Abstract The structural, microstructural and dielectric properties of the Ce doped Bi 0.5 Na 0.5 TiO 3 (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 ( e r = 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 Ce 3+ was substituted in Ti 4+ 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 Ce 3+ in Na + site instead of Ti 4+ 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 ( E F )), hopping length ( R H ), and hopping energies ( W H ) were calculated. The obtained results indicate that BNTC ceramics are suitable for promising industrial high performance piezoelectric applications.