The copper silver selenide has two phases: the low-temperature semimetal phase (α-CuAgSe) and high-temperature phonon-glass superionic phase (β-CuAgSe). In this work, the electric transport and thermoelectric properties of the two phases are investigated. It is revealed that the β-CuAgSe is a p-type semiconductor and exhibits low thermal conductivity while the α-CuAgSe shows metallic conduction with dominant n-type carriers and low electrical resistivity. The thermoelectric figure of merit zT of the polycrystalline β-CuAgSe at 623 K is ~0.95, suggesting that superionic CuAgSe can be a promising thermoelectric candidate in the intermediate temperature range.

The solubility of Yb in Yb x Co 4 Sb 12 was reported to be 0.19 in bulk skutterudites made by melting and slow cooling method. Surprisingly we increased x close to 0.5 by a special sample preparation method: ball mill and hot press. We show that a higher Yb concentration not only increases the power factor due to a higher electron concentration but also reduces the thermal conductivity k because of stronger phonon scattering. In this way, we have achieved a dimensionless thermoelectric figure of merit ZT of about 1.2 at 550°C in Yb 0.35 Co 4 Sb 12 .

Effect of ceramic dispersion on thermoelectric properties of nano-ZrO 2 ∕ CoSb 3 composites

Good thermoelectric materials should have low thermal conductivity, high electrical conductivity, and Seebeck coefficient, which cannot be easily balanced in bulk materials. Exceptionally, the super-ionics in β-Cu2Se can favorably contribute large ionic electrical conductivity and a liquid-like thermal conductivity by Cu+ ions. In the previous work, the superionic mechanism was found to be enhanced by small and randomly orientated lamellae with alternating ordered Se ion monolayer and disordered Cu ion bilayers. Here, we further enhance the superionic mechanism by increasing and better aligning lamellae in bulk Cu1.94Al0.02Se, resulting in a large thermoelectric figure of merit of 2.62 at 756 °C.