具有c轴择优的CuCr1-xMgxO2多晶的热电输运性质及Mg掺杂效应  

Thermoelectric Transport Properties and Mg Doping Effect of CuCr1-xMgxO2 Polycrystals with c-Axis Orientation

作　　者：崔凯 虞澜[1] 刘安安 秦梦[1,2] 宋世金[1] 沈艳 CUI Kai;YU Lan;LIU Anan;QIN Meng;SONG Shijin;SHEN Yan(Faculty of Materials Science and Engineering,Kunming University of Science and Technology,Kunming 650093;Shanghai Institute of Ceramics,Chinese Academy of Science,Shanghai 200050)

机构地区：[1]昆明理工大学材料科学与工程学院,昆明650093 [2]中国科学院上海硅酸盐研究所,上海200050

出　　处：《材料导报》2019年第20期3363-3366,3371,共5页Materials Reports

基　　金：国家自然科学基金(51462017; 51262016)~~

摘　　要：采用固相反应法制备了c轴择优的CuCr1-xMgxO2(0≤x≤0.08)系列多晶,通过X射线衍射、扫描电镜和电阻率-温度曲线、Seebeck系数-温度曲线对样品的结构、热电输运和固溶度进行表征研究。随Mg掺杂量在x=0~0.03范围内增加,多晶为铜铁矿单相结构,层状晶粒在ab面显著长大,(00l)取向因子最大达0.53,晶界和孔隙显著减少,致密度依次提高;多晶呈热激活机制的半导体电输运行为,热激活能从0.273eV下降到0.031eV,室温电导率相应提高了3~4个数量级,高温下Seebeck系数从481.2μV·K^-1减小到334.7μV·K^-1。由于声子曳引的贡献,随温度升高,掺Mg样品的Seebeck系数增大。x>0.03后,样品的热电输运性质基本保持不变,微观结构变化不大,在晶界处观察到MgCr2O4八面体尖晶石第二相,分析认为Mg掺杂的最大固溶度约为0.03。随Mg^2+替代Cr^3+的增加,在靠近价带顶的上方引入受主能级并展宽,使电输运的热激活能显著下降,空穴载流子浓度增大;同时c轴择优取向使面内的输运分量增加,这都是电导率提高的主要原因,而载流子迁移率浮动是电导率提高的次要原因。CuCr1-xMgxO2(0≤x≤0.08)polycrystalline samples with c-axis orientation were prepared by solid-state reaction.The microstructure and thermoelectric transport properties of the samples were characterized by X-ray diffraction,scanning electron microscopy,resistivity-temperature and Seebeck coefficient-temperature curves.In the single-phase delafossite structure with increasing Mg doping amount within x=0-0.03,the crystal grains grow significantly along the ab-plane and(001)lotgering factor is up to 0.53,the grain boundary and pore decrease significantly,and the density increases successively.The polycrystalline samples exhibit semiconducting electrical transport behavior according with Arrhenius thermal activation mode.The activation energy decreases from 0.273 eV to 0.031 eV,and the conductivity increases by 3-4 orders of magnitude at room temperature,the Seebeck coefficient at high temperature decreases from 481.2μV·K^-1 to 334.7μV·K^-1 and increases with the increasing temperature which due to the contribution of phonon drag in the Mg-doped samples.After x>0.03,the thermoelectric transport remain basically unchanged,the polycrystalline microstructure changes little,and the MgCr2O4 octahedral spinel phase is observed at the grain boundary.In conclusion,the maximum solid solubility of Mg doping is 0.03.As Mg^2+replace the Cr^3+sites,they introduce an acceptor level and expanding near the top of the valence band,causing the thermal activation energy of the electrical transport drops significantly.The increased hole carrier concentration and the stronger c-axis orientation with more transport component in ab-plane are mainly account for the conductivity enhancement.The effect of carrier mobility is secondary.

关 键 词：CuCr1-xMgxO2多晶 固溶度 电导率 热激活能 SEEBECK系数 

分 类 号：TB34[一般工业技术—材料科学与工程]