Polycrystalline SnP3: Synthesis, Metallic Transport, and Thermoelectric Implications

Abstract

Polycrystalline SnP3 was synthesized via a combined process of high-energy ball milling, two-step spark plasma sintering, and thermal annealing. X-ray diffraction confirms the formation of phase-pure rhombohedral SnP3, with intermediate annealing effectively eliminating secondary phases. The sintered pellets exhibit dense microstructures with plate-like grains, consistent with the layered crystal structure. Transport measurements reveal metallic behavior, characterized by a high electrical conductivity of ~2.1 × 106 S m−1 at 300 K and a small positive Seebeck coefficient of ~6.5 μV K−1. The thermal conductivity is ~15 W m−1 K−1 with weak temperature dependence, indicating dominant electronic heat transport. Effective medium analysis suggests that incorporating SnP3 into a p-type thermoelectric matrix can enhance electrical conductivity while preserving a moderate Seebeck coefficient, highlighting its potential for thermoelectric composite design.