七铝酸十二钙电子化合物研究进展  

Advances in the Study of C12A7:e^-Electride

作　　者：陈洁 张忻[1] 刘洪亮[1] 肖怡新 李凡 冯琦 赵伟康 刘燕琴[1] 张久兴[1,2] CHEN Jie;ZHANG Xin;LIU Hongliang;XIAO Yixin;LI Fan;FENG Qi;ZHAO Weikang;LIU Yanqin;ZHANG Jiuxing(Key Laboratory of Advanced Functional Materials of Ministry of Education,College of Materials Science and Engineering,Beijing University of Technology,Beijing 100124,China;School of Materials Science and Engineering,Hefei University of Technology,Hefei 230009,China)

机构地区：[1]北京工业大学材料科学与工程学院,新型功能材料教育部重点实验室,北京100124 [2]合肥工业大学材料科学与工程学院,合肥230009

出　　处：《材料导报》2020年第13期13076-13083,共8页Materials Reports

基　　金：北京自然科学基金(2112007);中央高校基础研究基金(PXM2019-014204-500032)。

摘　　要：钙铝石电子化合物[Ca 24 Al 28 O 64]4+:4e^-(C12A7:e^-)作为一种极具潜力的透明导电氧化物,自2002年进入人们的视野以来,就掀起了研究热潮,其制备工艺及应用在短短几年内取得了非常可观的发展。相较于其他电子化合物,它具有较好的化学稳定性,在450℃以下的空气中可以稳定存在。此外C12A7:e^-的独特纳米笼状结构使其具有较低的逸出功、较好的耐离子轰击能力以及可控的电性能,因此它在真空电子器件、催化化学反应以及超导等领域有着巨大的应用潜力。与传统阴极材料相比,它有两大优势:(1)逸出功低,比常见金属元素Ni(5.0 eV)、Mo(4.6 eV)以及LaB 6(2.67 eV)都要低;(2)耐离子轰击,阴极工作时因离子轰击而产生的溅射效应决定着阴极的寿命,而C12A7晶体中较强的化学键力使得它有着更加优良的耐离子轰击性能。此外,还有研究者在拓展该材料在催化剂载体、荧光灯、OLED等方面的应用。然而,C12A7:e^-的制备周期过长、还原条件苛刻、还原后电子浓度较低等难题一直制约着该材料的发展和应用。因此,近年来除深入探究该材料的应用外,研究者们还从开发高效快捷的多晶、单晶以及薄膜制备工艺方面不断尝试,并取得了丰硕的成果,在充分发挥C12A7:e^-应用优势的同时大幅缩短了制备周期并提高了电子浓度。目前,所制备的C12A7:e^-的电子浓度可达2.3×10^21 cm^-3,接近理论电子浓度2.33×10^21 cm^-3;在室温下的电导率也由2002年的0.3 S·cm^-1跃升至1380 S·cm^-1。自2002年Hayashi发现被紫外线照射后的C12A7:H-会由绝缘体变成电导体C12A7:e^-后,广大学者便致力于开发更加高效快捷的制备方法。2003年,Matsuishi等利用Ca金属气氛还原法制得了高电子浓度(2×10^21 cm^-3)的C12A7:e^-,但该方法会在样品表面形成致密的CaO薄膜而阻碍还原的继续进行,导致还原时间过长。此后,Hosono用Ti取代Ca金属有效缩短了�I n 2002,researchers at the Tokyo Institute of Technology synthesized a new inorganic mayenite electride-12CaO·7Al 2O 3:2e^-(hereinafter C12A7:e^-),as a potential transparent conductive oxide,which opened a new chapter in electride synthesis and utilization.Compared with other organic electrides,it has better chemical stability and can be stable in air below 450℃.This thermally stable electride has a number of potentially useful properties,such as air-stability,low work function,excellent performance in resisting poisoning,and metallic conductivity.Thermal stability and low reactivity with air make this material has a broad application prospect in electron emitter,optical device,catalyst support and other fields.Especially,C12A7:e^-has been found to have certain emission performance at low temperature and is very suitable as a electron emission material for low-power vacuum electronic devices.Compared with commercialized cathode materials,such as Ni(5.0 eV),Mo(4.6 eV)and LaB 6(2.67 eV),C12A7:e^-exhibits low work function(~2.4 eV).On the other hand,the strong chemical bond force in C12A7 crystal makes it have better ion bombardment resistance.The sputtering effect of ion bombardment on the cathode at work has an impact influence on the service life.Furthermore,the search for other inorganic electrides is a very promising area of study.Due to the prolonged synthesis cycle and special encapsulation,in the past decade,substantial efforts have been devoted to seeking simple and efficient route to acquire the electride in desire forms.So far,various forms of mayenite electride have been realized,mainly including single crystal,thin film and polycrystalline.These researchers have been working to make full use of the advantages of C12A7:e^-applications while significantly reducing the preparation cycle and increasing the electron concentration.Now,the electron concentration of C12A7:e^-can reach 2.3×10^21 cm^-3,which is close to the theoretical electron concentration of 2.33×10^21 cm^-3.The conductivity at room temp

关 键 词：C12A7:e^-电子化合物 还原 单晶 块体 薄膜 

分 类 号：TJ430.4[兵器科学与技术—火炮、自动武器与弹药工程]