1：Experimental Design and Method Selection:

A series of codoped Ge1?2xTe(CuSb)x (x = 0.025, 0.05, 0.075, 0.10) compounds were prepared through traditional solid reaction. The synergistic effect of Cu/Sb codoping on GeTe was investigated, focusing on tuning carrier concentration and reducing thermal conductivity. Theoretical models included density functional theory (DFT) for electronic structure analysis and the Debye-Callaway model for phonon transport.

2：025, 05, 075, 10) compounds were prepared through traditional solid reaction. The synergistic effect of Cu/Sb codoping on GeTe was investigated, focusing on tuning carrier concentration and reducing thermal conductivity. Theoretical models included density functional theory (DFT) for electronic structure analysis and the Debye-Callaway model for phonon transport. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples were synthesized from high-purity constituent elements (Ge, Te, Cu, Sb) in evacuated quartz tubes. Data on electrical and thermal properties were collected from synthesized pellets.

3：List of Experimental Equipment and Materials:

Equipment included spark plasma sintering (SPS, SPS-211Lx, Fuji Electronic Industrial Co., Ltd.), X-ray diffractometer (Bruker D8), SEM (Hitachi SU-8010), TEM (FEI Tecnai G2 F20), Namicto-III S/electric resistance measuring system (Namicro-3L, Wuhan Joule Yacht Science & Technology Co., Ltd.), laser flash diffusivity apparatus, DSC STA 409PC Netzsch, and Ecopia HMS-3000 Hall measurement system. Materials included Ge (99.99%), Te (99.999%), Cu (99.99%), and Sb (99.99%).

4：99%), Te (999%), Cu (99%), and Sb (99%). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The mixture was heated at 723 K for 12 h and 1273 K for 6 h, quenched in water, annealed for 3 days, ground to powder, and compacted by SPS at 773 K for 5 min. Phase structure was analyzed by XRD, microstructure by SEM and TEM, electrical properties (σ and S) measured from 323-773 K in He atmosphere, thermal diffusivity by laser flash, specific heat by DSC, density by Archimedes principle, and Hall coefficient at room temperature.

5：Data Analysis Methods:

Data analysis included Rietveld refinement for lattice parameters, DFT calculations for DOS and defect formation energy, and Debye-Callaway model for phonon scattering mechanisms. Statistical techniques involved calculating power factor, thermal conductivity, and zT values.