Boosting Thermoelectric Properties of AgBi₃(Se_yS_1–y)₅ Solid Solution via Entropy Engineering

Abstract

AgBi3S5 is an environmentally friendly n-type thermoelectric material composed of earth-abundant and nontoxic elements. It has a complex monoclinic structure with distorted NaCl-type fragments, which provide its intrinsically low thermal conductivity. However, poor electrical properties limit its overall performance. Configurational entropy engineering is an effective method to enhance thermoelectric properties. With the increase of configurational entropy, phonon point defect scattering is amplified, yielding lower lattice thermal conductivity, while the structure symmetry can also be improved, which leads to the enhanced electrical transport property. In this study, we combine carrier modulation and entropy engineering, utilizing melting–annealing and spark plasma sintering, to synthesize a series of AgBi3(Se y S1–y )5.08 bulks. Se substitution effectively increases the configurational entropy and thus dramatically decreases the thermal conductivity. Moreover, anion deficiency modulation effectively optimizes the carrier concentration and the electrical transport properties. Due to a power factor of 2.7 μW/(cm·K2) and a low thermal conductivity of 0.45 W/(m·K) at 723 K, the AgBi3(Se0.9S0.1)5.08 sample possesses the highest ZT of 0.42 at 723 K, nearly double the value of AgBi3S5.08 or pristine AgBi3S5. Our work demonstrates that apart from carrier optimization, entropy engineering opens a new avenue for enhancing the thermoelectric properties of a given material.

Enhancing Thermoelectric Performance of AgSbTe2-Based Compounds via Microstructure Modulation Combining with Entropy Engineering

“…Moreover, AgBi 3 S 5 is a material with intrinsic low thermal conductivity. With entropy engineering, the AgBi 3 (S 0.5 Se 0.5 ) 5.08 compound reaches a lattice thermal conductivity of 0.44 W m –1 K –1 at room temperature, 40% lower than that of the pristine sample . Therefore, tuning the configurational entropy can effectively enhance the thermoelectric performance …”

Achieving High Thermoelectric Properties of Cu2Se via Lattice Softening and Phonon Scattering Mechanism

“…Practically, the introduction of entropy engineering into the TE material can create a sustaining role of strong atomic disorder, which can effectively inhibit the unprofitable phase transition and systematically hinder the phonon transport. The entropy engineering concept has been widely available in a large amount of TE materials, such as SnTe, AgMnSbTe 3 , AgSbTe 2 , Pb 0.89 Sb 0.012 Sn 0.1 Se 0.5 Te 0.25 S 0.25 , and so forth., , providing a beneficial contribution to improve the TE properties. In addition, phonon scattering can be engineered in TE materials by the inhomogeneous internal strain field such as dislocations and precipitates, leading to the variation of the phonon transport path.…”

Enhancement of the Thermoelectric Performance of Cu2GeSe3 via Isoelectronic (Ag, S)-co-substitution

“…In general, excellent thermoelectric materials are considered to have high S , high σ, and low κ tot . − Unfortunately, these transport parameters of S , σ, and κ tot are generally interdependent, and the significant increase in ZT is a long-term challenge in the thermoelectric field. At present, a large number of reports of increased ZT value have all been made by increasing the power factor ( PF ) and decreasing the κ l values. − The chemical doping, energy filtering, and band structure engineering have been effective strategies for acquiring a high PF , and multi-scale phonon scattering and nanometer structure are considered to be effective strategies for decreasing κ l values. − …”