Energy‐Efficient Synthesis and High Thermoelectric Performance of α‐Cu2−ySe1−xTex

• Published in: ChemSusChem 2021-03, Vol.14 (5), p.1316-1323
• Main Authors: Lin, Fei‐Hung, Liu, Chia‐Jyi
• Format: Article
• Language: English
• Subjects: Clean energy; Cold pressing; Copper selenides; Energy consumption; Gas mixtures; inorganic chemistry; nanostructuring; Power factor; Reaction mechanisms; Reducing agents; Room temperature; room-temperature synthesis; Sintering (powder metallurgy); Synthesis; Te-doped Cu2Se; Thermoelectricity; thermoelectrics
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202002748

The high‐temperature phase of β‐Cu2Se always appears as the major phase for the reaction carried out using chemical solution methods. Here, a procedure was developed that could fabricate a single phase of α‐Cu2Se1−xTex (x=0.02 and 0.04) by room‐temperature aqueous synthesis using NaBH4 as reducing agent followed by cold pressing and sintering at 650 °C for 6 h in a flowing gas mixture of 20 % H2 and 80 % N2. The energy‐efficient synthesis carried out at room temperature abides by the 6th principle for green chemistry with less energy consumption. The reaction mechanism was studied, and evidence was provided of α‐Cu2Se being formed via the reaction between elemental Cu and Se atoms at room temperature. The resulting materials were characterized by powder X‐ray diffraction, field‐emission scanning electron microscopy, thermoelectric transport measurements, and Hall measurements. Cu1.96Se0.96Te0.04 had the highest power factor of 11 μW cm−1 K−2 at 818 K, and Cu2Se0.96Te0.04 had the maximum zT≥1.4 at T≥920 K among this series of materials. It's just a phase: α‐Cu2Se fabricated by wet‐chemical method transforms to β‐Cu2Se without the effect of temperature. In this work, Cu2−ySe1−xTex is synthesized using aqueous solution method at room temperature followed by consolidation in a flowing gas mixture of 20 % H2 and 80 % N2 at 650 °C for 6 h and then under vacuum at 650 °C for another 6 h. As an effect of Te‐doping, Cu2Se0.96Te0.04 has the maximum zT≥1.4 at T≥920 K.