Effect of Mn Doping on the Morphological and Optical Properties of Ba0.92Sr0.08Ti1-xMnxO3 Materials for Microwave Device Applications

In this work, we investigated the impact of Mn substitution on the morphological, structural, and optical properties of barium strontium titanate (BST) with the formula Ba_0.92Sr_0.08Ti_1−xMn_xO₃ (x = 0.00, 0.10, 0.20) fabricated using the solid-state reaction technique. The morphological and structural properties were studied using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The optical properties of the samples were analyzed using photoluminescence (PL), Fourier transform infrared (FTIR), and Raman spectroscopy. SEM micrographs displayed nearly spherical grains. The phase formation, lattice structure, crystallite size (D), strain (ε), and dislocation density (δ) of the Mn-doped BST ceramics were examined from the recorded XRD patterns using the Scherrer and Williamson–Hall (W–H) models, which showed that the crystallite size increased and the lattice strain and dislocation density decreased with increasing doping concentrations. FTIR results for the pristine sample of BST revealed that the absorption peak at a wavenumber of 470 cm⁻¹ was shifted to 1250 cm⁻¹ for Mn-doped BST concentrations. The Raman results indicated that the number of modes decreased with the increase in the Mn²⁺ concentrations. PL spectra showed an emission band centered at 60–659 nm, indicating redshift behavior. The analysis using XRD, SEM, FTIR, and Raman spectroscopy revealed that the concentration x = 0.20 is appropriate for use in microwave devices and other electro-optical applications.