Phase Evolution, Dielectric Anomalies, and Electrical Relaxations in Lead-Free Ba₀.₉₅Ca₀.₀₅TiO₃ Ceramics

Lead-free ferroelectric ceramics have gained widespread interest as alternatives to toxic lead-based dielectrics. In this work, Ba₀.₉₅Ca₀.₀₅TiO₃ (BCT) ceramics were synthesized via the conventional solid-state reaction route and evaluated for their structural and dielectric characteristics. X-ray diffraction combined with Rietveld refinement confirmed the formation of dense ceramics with a tetragonal perovskite structure (P4mm) after calcination at 850 °C and sintering at 950 °C, with refined lattice parameters a = 3.9895 Å, c = 4.0114 Å and c/a = 1.0055. The nanocrystalline microstructure remained stable, with an average crystallite size of ~26 nm and minimal lattice strain, demonstrating uniformity of the phase. Raman spectroscopy further supported the tetragonal symmetry through distinct E(TO) and A₁ vibrational modes, underlining the structural robustness of the synthesized ceramics. Dielectric investigations revealed a high permittivity of ~600 at 100 Hz and 50 °C, while a stable dielectric response was maintained between 10 kHz and 1 MHz across 100–450 °C. Importantly, dielectric loss remained below 0.1 throughout this operational range, confirming excellent thermal–frequency stability and low energy dissipation. Impedance and electric modulus analyses highlighted the presence of non-Debye type relaxation, defect-mediated hopping conduction, and clear distinction between grain and grain boundary contributions. The combination of phase purity, nanocrystalline stability, and superior dielectric response demonstrates the potential of BCT ceramics as environmentally benign candidates for next-generation capacitors, high-temperature sensors, actuators, and energy-storage devices.