Temperature-dependent dielectric behaviour and XRD analysis of Bi2Te2.8Se0.2

X-ray diffraction and temperature-dependent dielectric measurements were used to examine the structural and dielectric characteristics of Bi₂Te_2.8Se_0.2, a promising thermoelectric material. In evacuated quartz ampoules, high-purity Bi, Te, and Se powders were created using a solid-state process, The samples were annealed for 12 h at 723 K and gradually cooled to room temperature. A highly crystalline rhombohedral structure (space group R3̅m) with little lattice distortion (microstrain ~3.7%) after Se substitution was confirmed by Rietveld refinement of XRD data, improving structural stability. Because Se has a larger atomic radius than pure Bi₂Te₃, the unit cell volume increased slightly. The homogeneous grain distribution and clearly defined boundaries, which are essential for charge carrier mobility, were shown by scanning electron microscopy. At about 10 Hz, dielectric loss (tan δ) showed a Debye-type peaks signifying the greatest amount of energy released by polarization processes. At the peak frequency, the imaginary electric modulus verified relaxation dynamics with relaxation time τ = 0.016 s. The dielectric constant ε' rose gradually (by around 20%) at higher temperatures, indicating better polarizability for thermoelectric applications. In comparison to undoped versions, this work demonstrates the originality of Se-doping in Bi₂Te₃ for adjustable dielectric characteristics, attaining better efficiency (potential ZT > 1.2) with reduced synthesis costs. By associating improved performance of electrical devices with microstructure, these studies promote sustainable energy harvesting.