Investigation on structural and optical properties of system Sr₂Ce_1-xNa_xO₄ (0.0 ≤ x ≤ 0.10)

Powders of a few compositions of the system Sr₂Ce_1-xNa_xO₄ (x = 0, 0.02, 0.04, 0.06, and 0.10) have been prepared by the conventional solid-state reaction method. Analysis of the XRD patterns has shown a preference of dopant Na⁺ for the Sr²⁺ sites with increasing content of dopant (x). Rietveld refinement of the XRD patterns confirmed that each sample crystallized in orthorhombic structure with space group Pbam. The purity of the synthesized samples was further examined using Raman Fourier Transform Infrared (FTIR) spectroscopy techniques. Raman spectroscopy has further indicated the risk of decomposition of Sr₂CeO₄ phase with increasing doping concentration. Optical band gap energy computed using UV–visible absorption data (Tauc’s plot) falls between 2.91 and 3.10 eV, decreasing with increasing x. The shape of the excitation and emission spectra remains unchanged with increasing Na⁺ concentration. Two excitation peaks located around 290 nm and 350 nm are seen in photoluminescence (PL) excitation spectra. All Na-doped samples display an intense blue emission at 472 nm similar to undoped Sr₂CeO₄. SEM images of fractured surfaces of the sintered pellets have shown a significant role of Na doping on the morphology and grain size of the Sr₂CeO₄.