Structural, microstructural and optical characteristics of lead-free (1−x)(BiFeO₃)–x(CaTiO₃) ceramics in submillimeter region

Lead-free ceramic, (1−x)(BiFeO₃)–x(CaTiO₃) with x values of 0, 0.6, 0.7, 0.8 and 1.0 (0 ≤ x ≥ 1) were synthesized from BiFeO₃ (BFO) and CaTiO₃ (CTO) powders prepared by the chemical solution combustion method. Powder X-ray diffractogram revealed the structural features of the samples. FESEM results were analyzed to examine the microstructure of the samples. Terahertz (THz) region characteristics of polycrystalline BFO-CTO samples were investigated and reported in 0.2–3.5 THz range. Submillimeter spectroscopy (on a THz time-domain spectrometer) and Fourier transform infrared spectroscopy in the frequency range of 0.2 to 3.5 THz have been used to study the reflection infrared spectra of BiFeO₃ ceramic samples. In the 30 to 60 cm⁻¹ range, an additional absorption with a significant dielectric contribution has been found. It has been shown that the matching oscillators couple with both phonon modes with the lowest frequencies.