Thermoelectric　materials,　which　enable　direct　conversion　of　heat　into　electricity,　have　been　widely　investigated.　Among　these　materials,　GeTe-based　compounds　show　great　promise　for　thermoelectric　applications.　However,　conventional　synthesis　methods　struggle　to　preserve　the　high-performance　cubic　phase　(C-GeTe)　at　room　temperature　and　involve　multiple　time-consuming　and　energy-intensive　steps　such　as　long-time　heating　and　annealing　process.　To　address　this　problem,　we　developed　a　rapid　synthesis　strategy　combining　self-propagating　high-temperature　synthesis　in　vacuum-sealed　tubes　(SHS-V)　and　spark　plasma　sintering　(SPS).　Based　on　the　non-equilibrium　reaction　process,　we　successfully　realized　the　coexistence　of　the　high-temperature　cubic　phase　(C-GeTe)　and　the　rhombohedral　phase　(R-GeTe)　at　room　temperature　for　the　first　time,　which　weakened　electron-phonon　coupling　in　R-GeTe.　The　highly　symmetric　C-GeTe　optimized　carrier　concentration　while　enhancing　the　density-of-states　effective　mass,　significantly　improving　electrical　transport　properties.　Simultaneously,　the　phase　interfaces　and　fine　grains　formed　during　the　rapid　preparation　process　enhanced　phonon　scattering,　reducing　the　lattice　thermal　conductivity.　Ultimately,　a　comparable　ZT　value　of　1.24　was　achieved　at　773　K.　Such　a　rapid　synthesis　strategy　can　also　be　extended　to　other　thermoelectric　systems.　©　2025