Investigation on High-Temperature Thermoelectric Characteristics of β-Ga2O3

Abstract

The majority of waste heat sources are industrial steel and automobile where the operating temperature is higher than 673 K. However, the development of the thermoelectric (TE) field is still limited by low operating temperature, high-cost raw materials, and unstable device performance. β-Ga₂O₃ is endowed with nontoxic, eco-friendly, low-cost, and thermal stability advantages, which may be a potential high-temperature oxide thermoelectric material. Here, the capacitance–voltage (C–V) measurements and phonon-dominant thermal transport mechanism of β-Ga₂O₃ are revealed at first; lower lattice thermal conductivity of β-Ga₂O₃ will be obtained at a higher test temperature. Additionally, the electrical transport properties of β-Ga₂O₃ are further demonstrated by Seebeck coefficient and electrical conductivity at the segmented temperature range (323∼523 K; 873∼1073 K), indicating that regulation of carrier concentration is effective to optimize the TE performance. The maximum ZT of 0.237 is obtained for the sample with N_D = 6.1 × 10¹⁸ cm^–3 at 1073 K, whose increase is more than twice than that of another sample with N_D = 5.7 × 10¹⁷ cm^–3. As a result, β-Ga₂O₃ may be a promising candidate for high-temperature TE materials, which possesses great operating stability and durability in a harsh environment, especially for application scenarios where stability and performance are equally important.