An innovative CaSiO₃ dielectric material from eggshells by sol–gel process

Calcium silicate (CaSiO₃), wollastonite, with a molar ratio of CaO:SiO₂ of 1:1, was synthesized by a sol–gel process and sintered at 1,100°C for 1 h. The synthesis of calcium silicate was carried out using chicken eggshells as the starting material possessing several advantages such as low cost, high purity, and less moisture sensitivity, when compared with those obtained from metal alkoxide precursors via the sol–gel process. The CaSiO₃ samples have the triclinic or anorthic phase formations and good electrical properties. The dielectric constant and electrical conductivity are 62.59 ± 0.44 and 8.0052 × 10⁻⁴ (Ω.m)⁻¹, respectively, at 25°C and 1 MHz. The transmission electron microscopy (TEM) images of the samples show a good dispersion and uniform particles with an average diameter of about 0.5 nm. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Simultaneous thermal analysis (STA) were used to verify the synthesis.