Improved High‐Temperature Material Stability and Mechanical Properties While Maintaining a High Figure of Merit in Nanostructured p‐Type PbTe‐Based Thermoelectric Elements. Issue 5 (11th November 2022)

• Record Type: Journal Article
• Authors: Sauerschnig, Philipp; Jood, Priyanka; Ohta, Michihiro
• Is Part Of: Advanced materials technologies. Volume 8:Issue 5(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-11
• Subjects: contact resistance -- lead telluride -- mechanical properties -- power generation -- thermoelectrics; Materials science -- Periodicals; Technological innovations -- Periodicals; Materials science; Technological innovations; Periodicals; 620.1105
• DOI: 10.1002/admt.202201295
• Languages: English
• ISSNs: 2365-709X

Abstract

Abstract: Material stability and mechanical properties of nanostructured p‐type Pb0.993− x Na x Ge0.007 Te ( x = 0.02, 0.04) are improved by tuning dopant Na content, while maintaining a high thermoelectric figure of merit zT . Na‐rich impurity phases detrimental to the material stability, present in heavily Na‐doped p‐type PbTe, are absent after reducing the Na doping from 4% to 2%. The flexural strength of 2% Na‐doped p‐type PbTe measured at 773 K is significantly improved compared to that of the 4% Na‐doped p‐type PbTe, but lower than that of n‐type Pb0.98 Ga0.02 Te measured in comparison. Excellent thermoelectric performance is maintained for nanostructured Pb0.973 Na0.02 Ge0.007 Te ( zT ≈ 2.2 at 810 K). For n‐type Pb0.98 Ga0.02 Te, zT ≈ 1.3 at 760 K is confirmed. Single‐leg elements of Pb0.973 Na0.02 Ge0.007 Te and Pb0.98 Ga0.02 Te with Co80 Fe20 contact layers display maximum conversion efficiency ηmax ≈ 8.4% and ηmax ≈ 8.2% for temperature difference Δ T ≈ 470 K, respectively. After 240 h operation with Δ T ≈ 470 K, ηmax decreases by ≈33% for the p‐type and ≈13% for the n‐type legs. Lower ηmax compared to the estimation from the material properties and degradation during operation are attributed to crack formation due to thermal expansion mismatch between PbTe and Co80 Fe20 and sublimation from the hot side. Abstract : Several key issues related to the efficiency and reliability of thermoelectric modules based on nanostructured PbTe are addressed. High temperature material stability and mechanical properties in p‐type PbTe are improved while maintaining a high figure of merit zT by tuning dopant Na content. The degradation behavior of p‐ and n‐type PbTe‐based thermoelectric elements are investigated through long‐term power generation tests.