Structural, optical, and dielectric properties of Sol–gel derived Ca_0.6Sr_0.4La₄Ti₅O₁₇ layered perovskite

A_nB_nO_3n+2 is a type of oxygen-excess layered perovskites that has attracted significant attention from researchers in the field of electroceramics. In this study, the structural, optical, and dielectric properties of sol–gel derived Ca_0.6Sr_0.4La₄Ti₅O₁₇ layered perovskite were investigated. X-ray diffraction (XRD) analysis confirmed the formation of a single-phase monoclinic structure with space group P121/c1 (no. 14). Earlier, it was reported to crystallize into the orthorhombic structure with space group Pmnn. Therefore, Rietveld analysis was conducted to confirm the crystal structure with lattice parameters a = 7.7904 Å, b = 5.5185 Å, c = 31.4869 Å, β = 96.99° and cell volume of 1343.61 ų, followed by Raman spectroscopy which also confirmed the monoclinic structure. Scanning electron microscopy micrographs of the sample revealed elongated rod-like grains with 0.6 mm in length and 0.2 mm in width. Diffused reflectance spectroscopy (DRS) showed a direct bandgap of 5.31 eV and an indirect bandgap of 3.76 eV. Room temperature dielectric response versus frequency has been studied, which shows an almost constant relative permittivity (i.e., from 43 to 42) and a decreasing dielectric loss (from 0.12 to 0.0006) with an increase in frequency.