Fabrication process of ceramic capacitor derived from lead-free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ bulk and powder synthesized via sol–gel method

This study presents a comprehensive fabrication process for dielectric ceramic capacitor derived from lead-free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ (BNKT) in bulk and powder form, synthesized by sol–gel method. Both the BNKT powder and the bulk ceramic were rigorously analyzed and compared for their crystal structure, morphology, magnetic and optical properties. Through XRD and Raman results, the structure in the form of morphological phase boundary (MPB) was detected. In addition, the morphological structure, grain size evolution and purity of the samples were also confirmed by SEM and EDX. The weak ferromagnetic property of the BNKT powder sample was replaced by the diamagnetic property of the bulk ceramic sample and a decrease in the band gap (E_g) from 3.33 eV to 3.13 eV was also observed in the corresponding samples. At room temperature, the dielectric constant (ε_r) of the bulk ceramic reached 2193 with a dielectric loss (tanδ) of 0.332 at 1 kHz. It also exhibits typical ferroelectric behavior with slim P–E loop, a recoverable energy density (W_rec) of 12.541 mJ/cm³, and a high energy storage efficiency (η) of 46.44% under a low electric field of 15 kV/cm. Furthermore, the charge–discharge properties of BNKT dielectric ceramic capacitor were also characterized by a time constant (τ) of 8.452 μs. With this simple production process, it is possible to expand large-scale production while still ensuring the quality of ceramic capacitors, contributing to the development of BNKT lead-free material applications in electronic devices.