Phase Composition and Thermoelectric Properties of Materials Based on Cu2 – xSe (0.03 ≤ x ≤ 0.23)
Tóm tắt
The phase composition and thermoelectric properties of Cu2 – xSe 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 Cu2 – xSe 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 Cu2 – xSe 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 Cu2 – xSe increases because of the formation of copper vacancies. The change in the thermal conductivity substantially contributes to the thermoelectric figure of merit of Cu2 – xSe 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 Cu1.97Se composition.
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