NaDCC-Doped La 3 Se 4 Nanocomposites: Structural Fingerprinting and Thermal–Optical Insights

A chemical reduction-thermal annealing method was employed to synthesise La 3 Se 4 nanocomposites doped with sodium dichloroisocyanurate (NaDCC) and systematically studied to clarify the influence of NaDCC inclusion on their structural, morphological, thermal, and optical properties. X-ray diffraction confirmed the successful incorporation of the dopants by the formation of the nanocrystalline La 3 Se 4 phase without detectable secondary phases. The crystallite size was analysed by Scherrer, Monshi–Scherrer, Halder–Wagner and Sahadat–Scherrer models showing nanoscale size of 25–45 nm. Among them, Halder–Wagner method gave the most precise and reliable size range of 29–33 nm, and also showed the presence of microstrain due to doping. Hierarchically aggregated nanoscale particles with controlled surface roughness were observed by SEM and AFM analyses and EDX confirmed the presence of La, Se and Na in the nanocomposite. The DSC–TGA analysis showed excellent thermal stability up to 150 °C with multistep decomposition profile and a final residual mass of 39.53%. The UV–Vis spectroscopy revealed the direct optical band gap of 2.76 ± 0.03 eV, intense absorption resulting from allowed direct transitions, and transmittance of ~ 66% in the near infrared region. The high value of Urbach energy of 2.92 eV indicates the lattice disorder caused by dopants and the formation of band tails. The results show that NaDCC is a good modifier to tune the microstructural and optoelectronic properties of La3Se4 nanocomposites for potential semiconductor and photonic applications.