title: Investigation of the bipolar effect in the thermoelectric material CaMg2Bi2 using a first-principles study.
abstract: The bipolar effect in relatively narrow band-gap thermoelectric (TE) compounds is a negative process deteriorating the TE properties particularly at higher temperatures. In this work, we investigate the TE performance of the compound CaMg2Bi2 using the first-principles calculation and semi-classical Boltzmann transport theory in combination with our experimental data. It is revealed that this compound exhibits a remarkable bipolar effect and temperature-dependent carrier concentration. The bipolar effect imposes remarkable influence on all the electron-transport related TE parameters. An effective carrier concentration neff as a function of temperature is proposed to account for the bipolar effect induced carrier excitations. The as-evaluated TE parameters then show good consistency with measured results. This work may shed light on our understanding of the bipolar effect in TE compounds.
authors.affiliation: Laboratory of Solid State Microstructure and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. liujm@nju.edu.cn gongjijun@163.com.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gong
authors.forename: A J
authors.initials: AJ
authors.lastname: Hong
authors.forename: J
authors.initials: J
authors.lastname: Shuai
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: Z B
authors.initials: ZB
authors.lastname: Yan
authors.forename: Z F
authors.initials: ZF
authors.lastname: Ren
authors.forename: J-M
authors.initials: JM
authors.lastname: Liu