Research On The Preparation And Thermoelectric Properties Of BiCuSeO Based Thermoelectric Material

BiCuSeO is a promising thermoelectric material but needs acomplicated synthesis process.In this work,fine-grained BiCuSeO samples with high phase purity were synthesized by a combination of mechanical alloying(MA)and spark plasma sintering(SPS).The MA and SPS process parameters,reaction mechanism,thermoelectric properties and the alkaline earth metal-doped influence of BiCuSeO were all explored.The MA process parameters were firstly explored,the thermoelectric properties of the 500 rpm samples were better than that of the 400 rpm samples.With the MA rotate speed of 500 rpm,BiCuSeO can be synthesized after 7 hours.And the thermoelectric properties increased when prolong the MA time.It is also found that BiCuSeO compounds can be formed by the reaction between BiSe and CuO,after BiSe appeared firstly when using Bi,Se,and CuO as raw materials during MA process.The bulk pure-phase BiCuSeO samples were sintered by SPS,with the SPS temperature time and pressure of 973 K 5min and 50 MPa.The electrical conductivity of the corresponding bulk attains a modest enhancement due to the significantly increased carrier concentration although the carrier mobility was reduced compared with the sample prepared by classical solid-state reaction.The total thermal conductivity is below 0.7 W/mK in the whole measured temperature range,which is attributable to the increased defects and gain boundaries.As a result,a relatively high ZT value of 0.50 was obtained for the pristine BiCuSeO sample.In addition,Bi1-xCaxCu Se O were also synthesized by MA and SPS.When Bi was replaced by Ca element,the electrical transport property of the samples was improved with the thermal property was decreased at the same time,resulting in an enhancement of ZT in the whole measured temperature range.