Growth Techniques and Phase Characterization of Sn_1−xEr_xTe Crystals

Erbium-doped SnTe (Sn1−xErxTe) single crystals were synthesized to investigate the influence of erbium incorporation on phase stability, crystal structure, and thermophysical behavior relevant to thermoelectric applications. Single crystals with nominal compositions x = 0.00–0.10 were grown using the vertical Bridgman technique under controlled thermal conditions. X-ray diffraction analysis confirmed that at low erbium concentrations (x ≤ 0.02–0.03), erbium is substitutionally incorporated into the cubic NaCl-type SnTe lattice without detectable secondary phases. At higher erbium contents (x ≥ 0.05), Er-rich secondary phases such as ErTe and Er2Te3 precipitate within the SnTe matrix, indicating a limited solubility of erbium in SnTe. Differential thermal analysis revealed reproducible thermal effects associated with phase transformations and the formation of secondary phases at elevated dopant concentrations. Scanning electron microscopy combined with energy-dispersive spectroscopy showed microstructural refinement and increased defect density with increasing erbium content. Moderate erbium incorporation enhances phonon scattering, resulting in reduced lattice thermal conductivity and an increased Seebeck coefficient, whereas excessive doping leads to phase instability and degradation of electrical transport. These results demonstrate that erbium acts as an effective dopant for tuning the thermoelectric properties of SnTe within a narrow compositional window, while exceeding the solubility limit induces multiphase behavior and structural instability. The study provides experimentally grounded guidelines for controlled rare-earth doping and phase stability optimization in SnTe-based thermoelectric materials.