Material Parameter and Compatibility Factor Dependence of Maximum ZT in Cu and Ni-Based Thermoelectric

This work examines thermoelectric transport properties of Cu₂₋ₓSe, Cu₁₂Sb₄S₃, Sn₁₋ₓCuₓSe, Ti(Ni₁₋ₓCuₓ)Sn, NiTiX, and Ni₂CuCrFeAlₓ, representing a broad class of Cu- and Ni-based thermoelectric materials and their alloys. Using experimentally reported transport parameters, the electronic quality factor and the thermoelectric material parameter were evaluated for all compounds. Based on these values, systematic relationships between the maximum thermoelectric figure of merit, (ZT)max, and the material parameter B were constructed. A clear correlation between intrinsic electronic transport quality and achievable thermoelectric efficiency is observed, demonstrating that the material parameter B, evaluated using the Seebeck coefficient S, electronic quality factor BE, and lattice thermal conductivity λL, provides a predictive metric for ZT across diverse material classes. In addition, the temperature-dependent compatibility factor (CF) was calculated for all investigated systems. The CF analysis reveals that Cu-based chalcogenides maintain favorable compatibility over broad temperature ranges, indicating strong potential for segmented thermoelectric generator design, whereas Ni-based intermetallic and high-entropy alloys are intrinsically limited by suppressed compatibility factors. Overall, the results highlight a shift from power-factor-based evaluation toward device-oriented screening using the material parameter and compatibility factor, providing a unified framework for the rational design of high-performance thermoelectric materials.