摘要
[Ca24Al28O64]^4+(4e^–)电子化合物是一种具有高载流子密度、低逸出功的透明导电氧化物,但是繁琐的制备步骤、苛刻的工艺条件极大地限制了其实际应用.本文以特定化学计量比的Ca12Al14O33+CaAl2O4两相为前驱体,在放电等离子烧结系统里通过原位钙热反应成功制备了多晶C12A7:e^–.在烧结温度为1100℃,保温时间为10 min的条件下,其电子浓度基本达到理论最大值~2.3×10^21 cm^–3,在2.5 eV处出现明显的紫外吸收峰,致密度可达99%以上.同时用顺磁共振谱仪分析了其电子结构,结果呈Dyson特性,这些结果充分证明了电子有效地注入到笼腔结构中.热电子发射测试结果显示:在阴极温度为1373 K,外加电场为35000 V/cm的条件下, C12A7:e^–的热发射电流密度为1.75 A/cm^2,有效逸出功为2.07 eV.该工艺提供了一种新型的电子注入方法,大幅度缩短了制备周期使大规模生产成为可能.
[Ca24Al28O64]4^+(4e^–) eletride, as the first room-temperature stable inorganic electride, has attracted intensive attention because of its fascinating chemical, electrical, optical, and magnetic properties. However, it usually needs synthesizing through a complicated multistep process involving high temperature(e.g., 1350 °C),severe reduction(e.g., 700–1300 ℃ for up to 240 h in Ca or Ti metal vapor atmosphere) and post-purification.Owing to the H2O sensitivity of mayenite, the post-purification is quite troublesome once impurities are introduced. High-density, loosely bound encaged electrons with a low work function make it promise to possess practical applications. Therefore the facile method of massively producing the high-quality C12A7:e^– with high Ne is extremely desired. In this work, C12A7:e^– bulks are for the first time synthesized by simple spark plasma sintering process directly from a mixture of C12A7, CA and Ca powders under milder conditions(e.g., sintered at 1070 ℃ for 10 min in a vacuum). The obtained electride, which exhibits a relative density of 99%, an electron concentration of ~2.3×10^21 cm^–3 and an obvious absorption peak at 2.5 eV, is obtained via SPS process at 1100 ℃ for 10 min. Electronic structure is also investigated by electron paramagnetic resonance. The occurrence of Dysonian characteristic, a typical feature of good electronic conductors, strongly suggests that the electrons are trapped in mayenite cavities. Furthermore, the obtained C12A7:e^– exhibits good sinterabilty on a crystal scale of 5–40 μm. Thermionic emission test results show that the thermionic emission begins to occur at 700 K and a large current density of 1.75 A/cm2 is obtained in the electron thermal emission from a flat surface of the polycrystalline C12A7:e^– with an effective work function of 2.09 eV for a temperature of 1373 K with an applied electric field of ~35000 V/cm in a vacuum. Owing to no external reductant is needed, this developed route exhibits notable superiority over the
作者
李凡
张忻
张久兴
Li Fan;Zhang Xin;Zhang Jiu-Xing(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)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第20期246-251,共6页
Acta Physica Sinica
基金
国家自然科学基金(批准号:51371010,51572066,50801002)资助的课题~~
