Structural, optical and electrical characterizations of Ln₆WO₁₂ (Ln=La, Nd, Sm, Gd) nanoceramics

Nanoparticles of Ln₆WO₁₂ (Ln=La, Nd, Sm, Gd) abbreviated as LWO, NWO, SWO, and GWO are synthesised by combustion method. The synthesised materials are annealed at 900 C and then subjected to different characterization techniques. XRD studies show that LWO crystallizes in cubic structure and NWO, SWO, and GWO crystallize in tetragonal structure. The size and nature of the nanoparticles are characterized through the TEM analysis. The Raman and FTIR studies conducted on the samples support the structural data obtained from the XRD data. The UV-visible absorbance is recorded and optical bandgap is calculated using the Tauc's equation. The photoluminescence spectra of samples show that intense emission in green, blue, orange, and red regions and transitions responsible for the emissions are identified. Bulk ceramic pellets of LWO, NWO, SWO, and GWO prepared from their nanopowders are sintered and impedance studies are carried. The surface morphology of the sintered pellets of LWO, NWO, SWO, and GWO is studied by scanning electron microscopy. The frequency and temperature-dependent dielectric studies of prepared pellets are also carried out. (orig.)