# Synergistic Cu Doping and Yb Alloying Enhance Thermoelectric Performance of p‑Type Mg1.8Zn1.2Sb2‑Based Material toward High-Efficiency All-Mg3Sb2 Devices

## TL;DR

Researchers improved the performance of a thermoelectric material by combining copper doping and ytterbium alloying, enabling efficient waste heat recovery.

## Contribution

A synergistic approach of Cu doping and Yb alloying is introduced to enhance p-type Mg3Sb2 thermoelectric performance.

## Key findings

- A zT value of 0.95 was achieved for the optimized composition Mg1.18Cu0.02Zn1.2Yb0.6Sb2 at 673 K.
- A two-pair TE device reached an efficiency of 9.2% at a temperature difference of 374 K.
- A crack-free interface with low contact resistivity was achieved using cupronickel as a diffusion barrier.

## Abstract

AB
2Sb2-type Zintl
phases,
particularly Mg3Sb2-based materials, have recently
garnered significant attention owing to their earth-abundant, nontoxic
constituents and excellent n-type thermoelectric
(TE) performance in the medium temperature range. However, achieving
high-performance all Mg3Sb2-based TE devices
remains difficult due to the lack of a compatible and efficient p-type counterpart. Herein, a combined approach of Cu doping
and Yb alloying is employed to synergistically optimize the carrier
concentration, carrier mobility, and reduce lattice thermal conductivity,
thereby achieving a high-performance p-type Mg3Sb2 TE material. Consequently, a high zT value of 0.95 is obtained for the optimized composition Mg1.18Cu0.02Zn1.2Yb0.6Sb2 at
673 K. To demonstrate practical applicability, a fully compatible
Mg3Sb2-based TE device is fabricated using cupronickel
as a common diffusion barrier for both p- and n-type legs, ensuring excellent interfacial stability and
device reliability. A crack-free interface with a specific contact
resistivity of ρc ∼ 2.76 μΩcm2 is achieved. The single-leg p-type device exhibited a maximum
efficiency, ηmax ∼ 5.5%, while for a two-pair
TE device, ηmax ∼ 9.2% at a temperature difference
(ΔT) of 374 K is realized. These findings demonstrate
the potential of compositional engineering for developing efficient p-type Mg3Sb2 materials and fully
integrated TE devices for waste heat recovery.