This study presents the synthesis and comprehensive characterization of Fe 3 Se 4 and Fe 7 Se 8 nanoparticles using various techniques. The synthesis utilized the solid-state reaction technique, followed by thorough characterization using X-ray diffraction analysis to determine structural parameters like crystallite size and lattice constant. Field Emission Scanning Electron Microscopy revealed granular formations with average particle sizes of approximately 147, 189, and 222 for Fe 3 Se 4 , 4c-Fe 7 Se 8, and 3c-Fe 7 Se 8 nanoparticles, respectively. Thermogravimetric Analysis demonstrated the thermal stability of the materials up to 304, 386, and 384 °C, with subsequent weight losses for Fe 3 Se 4 , 4c-Fe 7 Se 8, and 3c-Fe 7 Se 8 nanoparticles. Dielectric spectroscopy tests across a broad frequency range revealed non-Debye-type responses, indicating complex relaxation phenomena. A thorough analysis of dielectric characterization is comprehensively presented in this paper.