Structural, dielectric, and energy storage properties of Na _0.375 Bi _0.375 Ca _0.25 TiO ₃ perovskite ceramic prepared via hydrothermal method

Dielectric capacitors based on ferroelectric compounds continue to attract attention due to their high power density and fast charge-discharge capabilities. However, achieving high energy density and efficiency in lead-free systems remains challeng-ing due to issues related to phase purity and microstructural control. This study aims to develop, using a hydrothermal method, a single-phase perovskite Na0.375Bi0.375Ca0.25TiO3 (NBCT) ceramic as a potential lead-free dielectric material. The synthesis process was optimized by adjusting the NaOH concentration to con-trol phase formation. A 12 M NaOH concentration successfully suppresses the for-mation of secondary phases. XRD and Rietveld refinement confirmed a tetragonal P4mm structure with B-site cation displacement along the [001] c-axis. Raman spec-tra exhibited features characteristic of a pseudocubic perovskite, consistent with the XRD-based structural model. The optical band gap, as determined from UV–Vis spectroscopy, was 3.08 eV. SEM-EDS results showed cubic-like grains averaging 240.98 nm with uniform elemental distribution. Dielectric measurements demon-strated a diffuse phase transition with a maximum dielectric constant at –45 °C and a Curie–Weiss exponent γ = 1.78. Ferroelectric measurements displayed a maximum polarization (Pm) of 6.73 μC/cm² and a remnant polarization (Pr) of 0.75 μC/cm² under an applied electric field of 80 kV/cm. Notably, the recoverable energy density reaches (Wrec) 218.9 mJ/cm³ with an efficiency (ղ) of 70.29%. These findings suggest that NBCT ceramics offer significant promise for the future devel-opment of environmentally friendly, high-energy-density dielectric capacitors.