Enhanced thermoelectric properties and electronic structures of p-type BiCu1−xAgxSeO ceramics

The thermoelectric properties and electronic structures were investigated on p-type BiCu1-xAgxSeO (x=0, 0.02, 0.05, 0.08) ceramics prepared using a two-step solid state reaction followed by inductively hot pressing. All the samples consist of single BiCuSeO phase with lamella structure and no preferential orientation exists in the crystallites. Upon replacing Cu+ by Ag+, maximum values of electrical conductivity of 36.6 S cm−1 and Seebeck coefficient of 350 μV K−1 are obtained in BiCu0.98Ag0.02SeO and BiCu0.92Ag0.08SeO, respectively. Nevertheless, a maximum power factor of 3.67 μW cm−1K−2 is achieved for BiCu0.95Ag0.05SeO at 750 K owing to the moderate electrical conductivity and Seebeck coefficient. Simultaneously, this oxyselenide exhibits a thermal conductivity as low as 0.38 W m−1 K−1 and a high ZT value of 0.72 at 750 K, which is nearly 1.85 times as large as that of the pristine BiCuSeO. The enhancement of thermoelectric performance is mainly attributed to the increased density of states near the Fermi level as indicated by the calculated results.