Effects of Ga content on thermoelectric properties of P-type Ba_8Ga_(l6)+_xZn_3Ge_(27-x), type-I clathrates

摘要

P-type Ba_8Ga_(16)+_xZn_3Ge_(27-x) (x = 0.1, 0.2, 0.3, and 0.4) type-I clathrates were synthesized by combining solid-state reaction with spark plasma sintering (SPS) tech_nology. The effects of slight increase of Ga content on thermoelectric properties have been investigated. The results show that at room temperature the carrier concentration Np of p-type Ba_8Ga_(16)+_xZn_3Ge_(27_x) clathrates increases remark_ably compared with that of Ba_8Ga_(16)Zn_3Ge_(27) compound, which results in the increases of electrical conductivity although carrier mobility __H slightly decreases. The thermal conductivity k of all samples increases with the increase of Ga content. Ba_8Ga_(16.2)Zn_3Ge_(26.8) compound exhibits the highest ZT value of 0.43 at '700 К, which is increased by 13% compared with that of Ba_8Ga_(16)Zn_3Ge_(27) compound