Role of La/Pr substitution in modulating the Dielectric and Ferroelectric response of SrBi6Nb2Ti3O21 Aurivillius ceramics

This paper reports a comprehensive study of two series of La- and Pr-substituted SrBi₆Nb₂Ti₃O₂₁ (SBNT) ceramics with La/Pr=0.04, 0.06, and 0.08, synthesized via the solid-state reaction route. Phase purity and lattice parameter variations were confirmed through XRD and Rietveld refinement. SEM analysis revealed plate-like grain morphology, while XPS results showed the presence of Pr³⁺, Pr⁴⁺ species in Pr- and a reduction in oxygen vacancies with La/Pr addition. Dielectric properties were studied over a temperature range of RT-750 °C and a frequency range of 20 Hz–1 MHz. An increase in ferroelectric transition temperature from ~667 °C to ~700 °C was observed with La/Pr substitutions. The dielectric responses elucidate an increase in RT dielectric constant by a factor of 11-13 relative to pristine SBNT ceramics in La, x=0.06 (SLBNT-6) and Pr, x=0.08 (SPBNT-8) compositions, respectively. Room-temperature P-E loop measurements showed enhanced remanent polarization (2P_r) in all doped samples compared to the pristine composition. Among these, the La=0.06 (SLBNT-6) and Pr=0.08 (SPBNT-8) compositions demonstrated enhanced ferroelectric polarization, with remanent polarization (2Pr) values of 1.15 μC/cm² and 1.72 μC/cm², respectively. These values represent a threefold and fourfold increase in 2P_r values compared to the pristine SBNT compound. These optimized samples also demonstrated energy storage capability and efficiency, as assessed via RT P-E loop measurements. The maximum energy densities recovered were determined to be 77.97 kJ/m³ and 67.08 kJ/m³ for SLBNT-6 and SPBNT-8 compositions of La³⁺ and Pr³⁺-modified ceramics, respectively.