Studies on structural, optical and microwave dielectric properties of double perovskite Sr₂Fe_1+xNb_1-xO₆, ceramics synthesized by solid state route

The solid solution of Sr2Fe1+xNb1-xO6, 0.015 <= x <= 0.030 double perovskite ceramics has been synthesized by mixed oxide route. In this paper, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy have been used to investigate the structure stability of double perovskite ceramics, Sr2Fe1+xNb1-xO6, 0.015 <= x <= 0.030 Impedance analysis and photoluminescence (PL) spectroscopy were used to investigate the ceramic's dielectric and optical properties respectively. The XRD pattern revealed the single phase tetragonal structure along with space group I4/m. The findings demonstrate that the binding strength and stability of double perovskite increase with increasing contents (x). Increasing frequency may encourage carrier hopping and mobility, but the free carrier may also be expected to conduct the bound charge at a high frequency. Fe3+ and Nb5+ replace smaller cations at the B-site, causing a cationic disorder that causes oxygen vacancies in the lattice skeleton and boosts conductivity. Tangent loss decreases with increasing frequency, which is reported in this work. According to the PL analysis, an excitation energy of 2.22 eV at a wavelength of 560 nm was measured, which is appropriate for the generating of green light lasers.