Influence of erbium substitution on structural, optical and dielectric properties of strontium hexaferrite

This paper reports the influence of erbium substitution on structural, electrical, dielectric and optical properties of SrFe_12-xEr_xO₁₉ (x = 0.0, 0.5, 1.0, 1.5 and 2.0) samples synthesized by sol-gel combustion method. Powder X-ray diffraction pattern analysis confirms the hexagonal structure of SrFe_12-xEr_xO₁₉ samples with space group P63 /mmc α-Fe₂O₃ phase is not present in the prepared samples. The value of lattice parameters (a and c) varies from 5.8561-5.8898 A and 22.742-23.0821 A, respectively. Morphological and elemental analyses were done by scanning electron microscopy and energy dispersive X-ray, respectively. Fourier-transform infrared spectroscopy spectra show the absorption band in the 402-620 cm^-1 region, which is due to Fe-O stretching vibration in the octahedral and tetrahedral sites. The band gap (E_g) of the SrFe_12-xEr_xO₁₉ samples decreases from 4.10 to 4.06 eV with Er³⁺ ions substitution. The photoluminescence (PL) emission spectra were observed at 364 nm. The value of dielectric constant decreases at higher frequency due to ceasing effect of polarization. The complex impedance spectroscopy analysis reveals that the prepared samples show non-Debye type dielectric relaxation behaviour. The increase in dielectric constant and decrease in dielectric loss with increasing Er³⁺ concentration makes the prepared samples a potential candidate for different device applications. (author)