Thermal Transport Properties of a Mixed Anion Layered Compound, Polycrystalline LaCu1-δS0.5Se0.5O (δ = 0.01)

Electrical and thermal transport properties of a polycrystalline carrier-doped wide-gap semiconductor LaCu 1- S 0.5 Se 0.5 O ( = 0.01), in which the CuCh (Ch = S, Se) layer works as conducting layer, were measured at temperatures 473~673 K.The presence of = 0.01 copper defects dramatically reduces the electrical resistivity () to approximately one part per million compared to that of = 0 at room temperature.The polycrystalline = 0.01 sample exhibited of 1.3 10 -3 m, thermal conductivity of 6.0 Wm -1 K -1 , and Seebeck coefficient (S) of 87 VK -1 at 673 K.The maximum value of the dimensionless figure of merit (ZT) of the = 0.01 sample was calculated to be 6.4 10 -4 at T = 673 K.The ZT value is far smaller than a ZT ~ 0.01 measured for a nominal LaCuSeO sample.The smaller ZT is mainly due to the small S measured for LaCu 1- S 0.5 Se 0.5 O ( = 0.01).According to the Debye model, above 300 K phonon thermal conductivity in a pure lattice is inversely proportional to T, while thermal conductivity of the = 0.01 sample increases with increasing T.