Structural, optical, vibrational, and dielectric properties of an Ni2+-doped Sr2MnWO6 double perovskite for wireless applications

Abstract

This study examined the effects of Ni²⁺ substitution on the structural, microstructural, optical, and dielectric properties of Sr₂(Mn_1−xNi_x)WO₆ (0.00 ≤ x ≤ 0.40) double perovskites using a normal processing approach. Each sample's monoclinic structure and space group (P21/n) were verified using the X-ray diffractometry (XRD) technique. Successful ionic substitution was indicated by the XRD results, which showed a systematic drop in lattice parameters and unit cell volume with increasing Ni²⁺ content. Along with a rise in the lattice strain and dislocation density, the average crystallite size shrank from 58 nm (x = 0.00) to 47 nm (x = 0.40), indicating increased structural deformation. Images from scanning electron microscopy (SEM) revealed dense, crystalline microstructures with average grain sizes that gradually decreased as the Ni²⁺ content increased. This might be explained by the difference in the ionic radii between the host and substitution elements. With Ni²⁺ concentrations, the band gap energy increased from 3.10 eV to 3.51 eV, as shown by the ultraviolet visible (UV-vis) spectrometry results. The photon excitation energy varied between 2.65 eV and 1.76 eV with Ni²⁺ concentrations, according to photoluminescence (PL) studies. Dielectric properties, such as the dielectric constant and tangent loss, have been shown to vary with frequency. Generally speaking, the structure and characteristics of Sr₂MnWO₆ are successfully modified by the addition of Ni²⁺, resulting in an appropriate band gap, low dielectric loss, and high dielectric permittivity.