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金属氧化物电子化合物[Ca24Al28O64]4+：4e-（C12A7：e-）因其天然的纳米尺度笼腔结构带来的新奇物理化学特性而在阴极电子源材料、超导和电化学反应等领域有着独特的应用价值.本文系统研究了以CaCO3和Al2O3粉末为原料，采用固相反应-放电等离子烧结-活性金属Ti还原相结合的方法制备C12A7：e-的工艺条件及其电输运特性.实验结果表明：在封装石英管真空度为10-5 Pa，还原温度为1100℃，还原时间为1030 h条件下，成功制得载流子浓度为约10181020 cm-3的C12A7：e-块体材料.第一性原理计算得到的C12A7：e-能带结构和态密度表明，笼腔内的O2-完全被e-取代后，C12A7：e-费米能级明显穿过笼腔导带，说明位于笼腔内自由运动的电子使C12A7从绝缘体转变成导体，同时费米面附近的笼腔电子易于从笼腔导带跃迁至框架导带，在电场或热场的作用下电子更容易逸出，这也是C12A7：e-逸出功低的主要原因.
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关键词:
- [Ca24Al28O64]4+:4e-电子化合物 /
- Ti还原 /
- 第一性原理计算 /
- 电输运特性
The[Ca24Al28O64]4+:4e- (C12A7:e-) electride composed of densely packed, subnanometer-sized cages. This unique structure makes it possess distinctive applications in fields of electronic emission, superconductor, electrochemical reaction. In this paper, we explore a new method to prepare the bulk of C12A7:e- electride. The following areare systematically studied in this work. 1) the condition of preparing bulk of C12A7:e- electride by solid reaction combining spark plasma sintering and reduction with Ti particles at high temperature, CaCO3 and Al2O3 powders are used as raw materials; 2) the first principle calculations of band structure and density of states of the C12A7:e- electride; 3) the analysis of the electrical transport properties of the C12A7:e- electride. The bulk of C12A7:e- electride is successfully prepared by this method, so the results show that the bulk of C12A7:e- electrode with the electron concentration 1018-1020 cm-3 is synthesized at 1100 ℃ and a vacuum pressure of 10-5 Pa for 10-30 h. In the process of Ti reduction, Ti particles become evaporated and deposit on the surface of C12A7, the free O2- atom in the cages diffuse to the sample surface, the Ti vapor reacts with the O2-, forming a loose TiO_x layer. In order to maintain electrical neutrality, the electrons of the free O2- atom leave from the cages, forming the C12A7:e- electride. In addition, the loose TiO_x layer also provides a channel for the diffusion of the O2- atoms in the cage, ensuring the continuation of the reduction reaction. The calculated band structure and density of states of the bulk C12A7:e- electride show that when electrons replace the O2- atoms in the cage, the Fermi level of C12A7:e- crosses over the cage conduction band (CCB). Thus the free movement of the electron is the main reason for the insulator C12A7 to convert into conductor C12A7:e-. At the same time the electrons near the Fermi level in the cages are easy to jump from the CCB to the frame conduction band (FCB). Combination of the above experimental results suggests that the electrons in cages are easier to escape to vacuum under the action of electric field or thermal field, which is the main reason for low work function of C12A7:e-. This way provides an new approach to the realization of the insulator C12A7 converting into C12A7:e- electride. And the C12A7:e- is a good electronic emission material due to low work function, low working temperature, and highly anti-poisoning ability, so this method of preparing bulk C12A7:e- electride provides a good new way to synthesize a new electronic emission material.[1] Kerrour W, Kabir A, Schmerber G, Boudjema B, Zerkout S, Bouabellou A, Sedrati C 2016 J. Mater. Sci.:Mater. Electron. 27 10106
[2] Kim S W, Matsuishi S, Nomura T, Kubota Y, Takata M, Hayashi K, Kamiya T, Hirano M, Hosono H 2007 Nano Lett. 7 1138
[3] Kurashige K, Toda Y, Matstuishi S, Hayashi K, Hirano M, Hosono H 2006 Cryst. Growth Des. 6 1602
[4] Kiyanagi R, Richardson J W, Sakamoto N, Yoshimura M 2008 Acta Cryst. 179 2365
[5] Watanabe S, Watanabe T, Ito K, Miyakawa N, Ito S, Hosono H, Mikoshiba S 2011 Sci. Technol. Adv. Mat. 12 034410
[6] Pan R K, Feng S, Tao H Z 2017 Mat. Sci. Eng. 67 1
[7] Yang S, Kondo J N, Hayashi K, Hirano M, Domen K, Hosono H 2004 Appl. Catal. A:Gen. 277 239
[8] Park J K, Shimomura T, Yamanaka M, Watauchi S, Kishio K, Tanaka I 2005 Cryst. Res. Technol. 40 329
[9] Miyakawa M, Kim S W, Hirano M, Kohama Y, Kawaji H, Atake T, Ikegami H, Kono K, Hosono H 2007 J. Am. Chem. Soc. 129 7270
[10] Li J, Yin B, Fuchigami T, Inagi S, Hosono H, Ito S 2012 Electrochem. Commun. 17 52
[11] Kitano M, Inoue Y, Yamazaki Y, Hayashi F, Kanbara S, Matsuishi S, Yokoyama T, Kim S W, Hara M, Hosono H 2012 Nat. Chem. 4 934
[12] Bao L H, Tao R Y, Tegus O, Huang Y K, Leng H Q, de Visser A 2017 Acta Phys. Sin. 66 186102 (in Chinese)[包黎红, 陶如玉, 特古斯, 黄颖楷, 冷华倩, Anne de Visser 2017 物理学报 66 186102]
[13] Kim S W, Hayashi K, Hirano M, Hosono H, Tanaka I 2006 J. Am. Ceram. Soc. 89 294
[14] Kim S W, Toda Y, Hayashi K, Hirano M, Hosono H 2006 Chem. Mater. 18 1938
[15] Toda Y, Matsuishi S, Hayashi K, Ueda K, Kamiya T, Hirano M, Hosono H 2004 Adv. Mater. 16 685
[16] Satoru M, Yoshitake T, Masashi M, Katsuro H, Toshio K, Masahiro H, Lsao T, Hideo H 2003 Science 301 626
[17] Cao D, Liu B, Yu H L, Hu W Y, Cai M Q 2015 Eur. Phys. J. B 88 75
[18] Liu B, Wu L J, Zhao Y Q, Wang L Z, Cai M Q 2016 Eur. Phys. J. B 89 80
[19] Wu L J, Zhao Y Q, Chen C W, Wang L Z, Liu B, Cai M Q 2016 Chin. Phys. B 25 107202
[20] Wang L Z, Zhao Y Q, Liu B, Wu L J, Cai M Q 2016 Phys. Chem. Chem. Phys. 18 22188
[21] Jiang P G, Wang Z B, Yan Y B, Liu W J 2017 Acta Phys. Sin. 66 246801 (in Chinese)[姜国平, 汪正兵, 闫永播, 刘文杰 2017 物理学报 66 246801]
[22] Sushko P V, Shluger A L, Hirano M, Hosono H 2007 J. Am. Chem. Soc. 129 942
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[1] Kerrour W, Kabir A, Schmerber G, Boudjema B, Zerkout S, Bouabellou A, Sedrati C 2016 J. Mater. Sci.:Mater. Electron. 27 10106
[2] Kim S W, Matsuishi S, Nomura T, Kubota Y, Takata M, Hayashi K, Kamiya T, Hirano M, Hosono H 2007 Nano Lett. 7 1138
[3] Kurashige K, Toda Y, Matstuishi S, Hayashi K, Hirano M, Hosono H 2006 Cryst. Growth Des. 6 1602
[4] Kiyanagi R, Richardson J W, Sakamoto N, Yoshimura M 2008 Acta Cryst. 179 2365
[5] Watanabe S, Watanabe T, Ito K, Miyakawa N, Ito S, Hosono H, Mikoshiba S 2011 Sci. Technol. Adv. Mat. 12 034410
[6] Pan R K, Feng S, Tao H Z 2017 Mat. Sci. Eng. 67 1
[7] Yang S, Kondo J N, Hayashi K, Hirano M, Domen K, Hosono H 2004 Appl. Catal. A:Gen. 277 239
[8] Park J K, Shimomura T, Yamanaka M, Watauchi S, Kishio K, Tanaka I 2005 Cryst. Res. Technol. 40 329
[9] Miyakawa M, Kim S W, Hirano M, Kohama Y, Kawaji H, Atake T, Ikegami H, Kono K, Hosono H 2007 J. Am. Chem. Soc. 129 7270
[10] Li J, Yin B, Fuchigami T, Inagi S, Hosono H, Ito S 2012 Electrochem. Commun. 17 52
[11] Kitano M, Inoue Y, Yamazaki Y, Hayashi F, Kanbara S, Matsuishi S, Yokoyama T, Kim S W, Hara M, Hosono H 2012 Nat. Chem. 4 934
[12] Bao L H, Tao R Y, Tegus O, Huang Y K, Leng H Q, de Visser A 2017 Acta Phys. Sin. 66 186102 (in Chinese)[包黎红, 陶如玉, 特古斯, 黄颖楷, 冷华倩, Anne de Visser 2017 物理学报 66 186102]
[13] Kim S W, Hayashi K, Hirano M, Hosono H, Tanaka I 2006 J. Am. Ceram. Soc. 89 294
[14] Kim S W, Toda Y, Hayashi K, Hirano M, Hosono H 2006 Chem. Mater. 18 1938
[15] Toda Y, Matsuishi S, Hayashi K, Ueda K, Kamiya T, Hirano M, Hosono H 2004 Adv. Mater. 16 685
[16] Satoru M, Yoshitake T, Masashi M, Katsuro H, Toshio K, Masahiro H, Lsao T, Hideo H 2003 Science 301 626
[17] Cao D, Liu B, Yu H L, Hu W Y, Cai M Q 2015 Eur. Phys. J. B 88 75
[18] Liu B, Wu L J, Zhao Y Q, Wang L Z, Cai M Q 2016 Eur. Phys. J. B 89 80
[19] Wu L J, Zhao Y Q, Chen C W, Wang L Z, Liu B, Cai M Q 2016 Chin. Phys. B 25 107202
[20] Wang L Z, Zhao Y Q, Liu B, Wu L J, Cai M Q 2016 Phys. Chem. Chem. Phys. 18 22188
[21] Jiang P G, Wang Z B, Yan Y B, Liu W J 2017 Acta Phys. Sin. 66 246801 (in Chinese)[姜国平, 汪正兵, 闫永播, 刘文杰 2017 物理学报 66 246801]
[22] Sushko P V, Shluger A L, Hirano M, Hosono H 2007 J. Am. Chem. Soc. 129 942
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