Abstract: Ca3Co4O9 polycrystalline bulks were respectively prepared via solid-state reaction sintering in air and further hot-press sintering in vacuum. The influences of hot-press sintering on the texture and electrical transport properties of polycrystals were comparatively studied by the measurements of XRD, SEM, density, temperature dependent resistivity curve and Hall effect. The results showed that the polycrystalline bulks prepared via two different methods were all of c-axis preferred orientation. The c-axis orie-ntation and density were significantly enhanced after hot-press sintering, while the crystallization quality declined slightly owing to oxygen deficiency after sintering in vacuum. The hot-press sintered polycrystal exhibited much lower resistivity which was only one-seventh of pressureless sintered sample′s at room temperature, and the resistivity increased with decreasing temperature. This was mainly due to the dominant electrical transportation along the crystal ab-plane and increased Co4+ carrier mobility resulting from the enhanced (00l) preferential texture and less scattering effects at grain boundaries and defects.
1 Brinks P, Van Nong N, Pryds N, et al. High-temperature stability of thermoelectric Ca3Co4O9 thin films[J]. Appl Phys Lett,2015,106(14):143903. 2 Ren G, Lan J, Zeng C, et al. High performance oxides-based thermoelectric materials[J]. J Mater,2015,67(1):211. 3 Song X, McIntyre D, Chen X, et al. Phase evolution and thermoelectric performance of calcium cobaltite upon high temperature aging[J]. Ceram Int,2015,41(9):11069. 4 Fergus J W. Oxide materials for high temperature thermoelectric energy conversion[J]. J Eur Ceram Soc,2012,32(3):525. 5 Yang G, Ramasse Q, Klie R F. Direct measurement of charge transfer in thermoelectric Ca3Co4O9[J]. Phys Rev B,2008,78(15):153109. 6 Masset A C, Michel C, Maignan A, et al. Misfit-layered cobaltite with an anisotropic giant magnetoresistance: Ca3Co4O9[J]. Phys Rev B,2000,62(1):166. 7 Sakai A, Kanno T, Yotsuhashi S, et al. Control of epitaxial growth orientation and anisotropic thermoelectric properties of misfit-type Ca3Co4O9 thin films[J]. Jpn J Appl Phys,2005,44(7):966. 8 Sakai A, Kanno T, Yotsuhashi S, et al. Preparation and anisotropic thermoelectric properties in misfit cobaltite thin films[C]// ICT 2005 24th International Conference on Thermoelectrics. Clemson,2005:288. 9 Tang G D, Guo H H, Yang T, et al. Anisotropic thermopower and magnetothermopower in a misfit-layered calcium cobaltite[J]. Appl Phys Lett,2011,98(20):202109. 10 Huang Y, Zhao B, Lin S, et al. Enhanced thermoelectric perfor-mance induced by misplaced substitution in layered Ca3Co4O9[J]. J Phys Chem C,2015,119(15):7979. 11 Fujii S, Yoshiya M. Manipulating thermal conductivity by interfacial modification of misfit-layered cobaltites Ca3Co4O9[J]. J Electron Mater,2016,45(3):1217. 12 Zhu Linle, Su Jinrui, Hou Linsen. Effects of Ag and La double-doping on the thermoelectric properties of Ca3Co4O9[J]. Mater Rev:Res,2014,28(8):86(in Chinese). 朱林乐,苏金瑞,侯林森. Ag、La双掺杂对Ca3Co4O9热电性能的影响[J]. 材料导报:研究篇,2014,28(8):86. 13 Rasekh S, Torres M A, Constantinescu G, et al. Effect of Cu by Co substitution on Ca3Co4O9 thermoelectric ceramics[J]. J Mater Sci: Mater Electron,2013,24(7):2309. 14 Wu T, Tyson T A, Bai J, et al. On the origin of enhanced thermoelectricity in Fe doped Ca3Co4O9[J]. J Mater Chem C,2013,1(26):4114. 15 Prasoetsopha N, Pinitsoontorn S, Kamwanna T, et al. Improvement of electrochemical properties of Ca3Co4O9 as anode materials for li-thium-ion batteries by Cr doping[J]. J Solid State Electrochem,2015,19(4):1197. 16 Shi Xun, Xi Lili, Zhang Wenqing, et al. Basic physics in thermoelectrics [J]. Physics,2011,40(11):710(in Chinese). 史迅, 席丽丽, 张文清, 等. 热电材料研究中的基础物理问题[J]. 物理,2011,40(11):710. 17 Song Shijin, Ni Jia, Yu Lan, et al. Thermoelectric properties and laser induced transverse voltage effect of polycrystalline Ca3Co4O9 with c-axis orientation[J]. J Chinese Ceram Soc,2015,43(3):286(in Chinese). 宋世金, 倪佳, 虞澜, 等. c轴择优Ca3Co4O9多晶的热电性质及激光感生横向电压效应[J]. 硅酸盐学报,2015,43(3):286. 18 Katsuyama S, Takiguchi Y, Ito M. Synthesis of Ca3Co4O9 ceramics by polymerized complex and hydrothermal hot-pressing processes and the investigation of its thermoelectric properties[J]. J Mater Sci,2008,43(10):3553. 19 Liu Wenjing, Meng Qingsen, Chen Shaoping, et al. Study on grain refinement and electrical properties of Ca3Co4O9+δ thermoelectric materials[J]. Mater Rev: Res,2014,28(4):24(in Chinese). 刘文静, 孟庆森, 陈少平, 等. Ca3Co4O9+δ热电陶瓷的晶粒细化及其电学性能研究[J]. 材料导报:研究篇,2014,28(4):24. 20 Wu N Y, Holgate T C, Van Nong N, et al. Effects of synthesis and spark plasma sintering conditions on the thermoelectric properties of Ca3Co4O9+δ[J]. J Electron Mater,2013,42(7):2134. 21 Kenfaui D, Chateigner D, Gomina M, et al. Anisotropy of the mechanical and thermoelectric properties of hot-pressed single-layer and multilayer thick Ca3Co4O9 ceramics[J]. Int J Appl Ceram Technol,2011,8(1):214. 22 Moon J W, Nagahama D, Maduda Y, et al. Anisotropic thermoelectric properties of crystal-axis oriented ceramics of layer-structured oxide in the Ca-Co-O system[J]. J Ceram Soc Japan,2001,109(1272):647. 23 Qiao Q, Gulec A, Paulauskas T, et al. Effect of substrate on the atomic structure and physical properties of thermoelectric Ca3Co4O9 thin films[J]. J Phys: Condensed Matter,2011,23(30):305005. 24 Klie R F, Qiao Q, Paulauskas T, et al. Observations of Co4+ in a higher spin state and the increase in the Seebeck coefficient of thermoelectric Ca3Co4O9 [J]. Phys Rev Lett,2012,108(19):196601. 25 Sedmidubsky D, Jakes V, Jankovsky O, et al. Phase equilibria in Ca-Co-O system [J]. J Solid State Chem,2012,194:199. 26 Mele P, Kamei H, Yasumune H, et al. Development of thermoelectric module based on dense Ca3Co4O9 and Zn0.98Al0.02O legs[J]. Metals Mater Int,2014,20(2):389.
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2017, Vol. 31 
