# Thermoelectric Property Mapping for High‐Performance Integrated MgAgSb‐MgCuSb System

## TL;DR

This paper maps thermoelectric properties of MgAgSb-MgCuSb to optimize both materials and interfaces for efficient thermoelectric modules.

## Contribution

A novel property mapping approach for integrated thermoelectric materials and interfaces in Mg-based systems.

## Key findings

- Ag-rich MgAgSb compositions achieve PF ∼21 µW cm−1 K−2 and zT = 1.12.
- Cu-rich MgAgSb compositions show low contact resistance and superior transport properties.
- A two-pair module with n-type Mg3Bi1.5Sb0.5 reaches 7.2% peak conversion efficiency.

## Abstract

To achieve high conversion efficiency in thermoelectric (TE) modules, not only thermoelectric materials (TEMs) with high figure‐of‐merit zT but also the optimization of thermoelectric interface materials (TEiMs) is required. For TEMs, enhancing zT relies on increasing power factor PF and lowering thermal conductivity κ, while for TEiMs, high electrical conductivity and κ are essential, which highlights the importance of the integrated design of TEMs and TEiMs. In this work, we select p‐type MgAgSb as the object and construct a TE property mapping of the integrated MgAgSb–MgCuSb two‐phase system by tuning the Ag/Cu ratio. Based on the thermoelectric property mapping, Ag‐rich compositions exhibit superior PF and zT values for TEM, maximized in PF∼21 µW cm−1 K−2, zT = 1.12 for MgAg0.97Cu0.03Sb. Conversely, Cu‐rich composition MgAg0.05Cu0.95Sb is identified as the optimal TEiM for its low contact resistance and superior carrier and phonon transport properties, reducing energy loss. A two‐pair thermoelectric module integrated with n‐type Mg3(Sb, Bi)2 is successfully fabricated, yielding a peak conversion efficiency of ∼7.2%, thereby advancing the performance of current Mg‐based TE modules. Overall, this study realizes the synergistic optimization of high‐performance TE materials and compatible TE interface materials, paving the way for the fabrication of efficient and scalable TE modules.

From the property mapping of the MgAgSb–MgCuSb system, both thermoelectric materials and corresponding interface materials are optimized: Ag‐rich compositions provide higher PF and zT, whereas Cu‐rich side yields superior transport properties and low contact resistance. A two‐pair module is also fabricated with n‐type Mg3Bi1.5Sb0.5, and it reaches an efficiency of ∼7.2% at ΔT = 293 K, demonstrating an effective strategy for high‐performance Mg‐based TE modules.