Dielectric anomaly, diffusivity and impedance behavior of transition metal substituted SrBi2NbTaO9 ferroelectric nano-ceramics prepared by chemical route

Highlights: • Substitution of smaller ionic radius at Sr- site leads to the distortion as well as oxygen vacancy in the ceramics. • Dielectric anomaly was clearly observed with diffused phase transition for Co-, Ni- and Cu- substituted sample. • The relaxation of all ceramics was clearly observed from dielectric and impedance study. • The high dielectric constant was observed for Sr0.5Cu0.5Bi2NbTaO9. -- Abstract: Dielectric, impedance, ac and dc conductivity of transition metal ions Co²⁺, Ni²⁺ and Cu²⁺ substituted at Sr- site of SrBi₂NbTaO₉ (SBNT) nanoceramics have been investigated throughout the manuscript. Nanosized Sr_0.5Co_0.5Bi₂NbTaO₉, Sr_0.5Ni_0.5Bi₂NbTaO₉ and Sr_0.5Cu_0.5Bi₂NbTaO₉ were synthesized by chemical precursor solution decomposition method. All of the ceramics showed orthorhombic structure proved from X-ray diffraction study that matched with JCPDS data file no. 86-1190. The unit cell volume, crystallite size, grain size were high for Sr_0.5Cu_0.5Bi₂NbTaO₉. Substitution of smaller ionic radius at Sr- site also leads to the distortion as well as oxygen vacancy in the ceramics that leads to the relaxor behavior of the materials. Dielectric anomaly was clearly observed with diffused phase transition for Cu-substituted sample. However, dielectric loss of Cu-substituted sample was little higher with respect to Ni- and Co- substituted SBNT ceramics. The relaxation of all ceramics was clearly observed from dielectric and impedance study. The high dielectric constant was observed for Sr_0.5Cu_0.5Bi₂NbTaO₉.