Enhanced pyroelectric and ferroelectric response in Mn- and Al-Co-substitution in NBT–NaNb ceramics via controlled sintering

Lead-free ferroelectric ceramics are intensively explored as environmentally benign alternatives to lead-based materials for multifunctional electronic applications. In this work, Mn- and Al-doped Na 0.5 Bi 0.5 TiO 3 –NaNbO 3 (NBTMn–BAl–NaNb) ceramics were synthesized using single- and double-sintering techniques to systematically evaluate the influence of processing conditions on their structural, dielectric, ferroelectric, and pyroelectric properties. X-ray diffraction analysis confirmed phase stability without secondary phases, while microstructural investigations revealed improved densification and grain uniformity in double-sintered ceramics. Ferroelectric polarization–electric field (P–E) measurements demonstrated a significant enhancement in electrical performance upon double sintering, with remanent polarization increasing from 45.34 to 55.04 μC/cm 2 and saturation polarization from 53.66 to 66.56 μC/cm 2 accompanied by a notable reduction in coercive field from 62.06 to 47.13 kV/cm. Temperature-dependent dielectric studies (RT–500°C) showed stable dielectric permittivity, a slight decrease in Curie temperature from 293 °C to 283 °C, and an upward shift in depolarization temperature from 100 °C to 110 °C, indicating improved thermal and polarization stability. Furthermore, the pyroelectric coefficient increased from 0.75 × 10 −4 to 0.9 × 10 −4 C m −2 °C −1 , while dielectric loss was substantially reduced from 1.0 to 0.4 in double-sintered samples, highlighting enhanced energy conversion efficiency. These results clearly demonstrate that double sintering is an effective processing strategy for optimizing microstructure and multifunctional performance, making NBTMn–BAl–NaNb ceramics promising candidates for lead-free energy storage, pyroelectric sensing, infrared detection, and thermal energy harvesting applications.