Abstract

The phase composition and thermoelectric properties of Cu_{2 – x}Se samples with different deviations from the stoichiometric composition (x = 0.03, 0.08, 0.13, 0.18, and 0.23) are studied. Bulk thermoelectric materials based on Cu_{2 – x}Se are synthesized by spark plasma sintering. The phase composition is studied using the X-ray diffraction method. Depending on the chemical composition, the materials based on Cu_{2 – x}Se at room temperature can be either a single-phase material containing only the cubic β-Cu₂Se phase or a two-phase material containing a mixture of monoclinic α-Cu₂Se and cubic β-Cu₂Se phases. It is shown that the deviation of the stoichiometric composition has a substantial effect on the electrophysical characteristics of the material. With an increase in the deviation of the stoichiometric composition, the concentration of the main charge carriers in Cu_{2 – x}Se increases because of the formation of copper vacancies. The change in the thermal conductivity substantially contributes to the thermoelectric figure of merit of Cu_{2 – x}Se compounds. In the investigated range of chemical compositions, the maximum values of thermoelectric figure of merit around ZT ~ 1.3 at 600°C are observed in samples with the Cu_1.97Se composition.

中文翻译：

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基于 Cu2 – xSe (0.03 ≤ x ≤ 0.23) 的材料的相组成和热电性能

摘要

研究了与化学计量组成 ( x = 0.03、0.08、0.13、0.18 和 0.23) 有不同偏差的 Cu _{2 – x} Se 样品的相组成和热电特性。基于 Cu _{2 – x} Se 的大块热电材料是通过放电等离子烧结合成的。使用 X 射线衍射方法研究相组成。根据化学成分的不同，室温下基于 Cu _{2 – x} Se的材料可以是仅包含立方 β-Cu ₂ Se 相的单相材料，也可以是包含单斜晶系 α-Cu 混合物的两相材料₂ Se 和立方 β-Cu ₂ Se 相。结果表明，化学计量组成的偏差对材料的电物理特性有重大影响。随着化学计量组成偏差的增加，由于铜空位的形成，Cu _{2 – x} Se 中主要电荷载流子的浓度增加。热导率的变化对 Cu _{2 – x} Se 化合物的热电品质因数有很大贡献。在所研究的化学成分范围内，在具有 Cu _1.97 Se 成分的样品中观察到在 600°C 下ZT ~ 1.3附近的热电品质因数的最大值。