多功能多元稀土六硼化物La_(1–x)Sr_(x)B_(6)光吸收及热电子发射机理

Optical absorption and thermionic emission mechanism of multi-functional La_(1-x)Sr_(x)B_(6) hexaborides

系统研究了多功能多元稀土六硼化物La_(1–x)Sr_(x)B_(6)纳米粉末的光吸收及多晶块体的热电子发射性能.纳米粉体光吸收结果表明,多元稀土六硼化物La_(1–x)Sr_(x)B_(6)透射光波长从591 nm至658 nm连续可调.多晶块体热电子发射结果表明,外加电压2000 V,阴极温度为1773 K时,热电子发射电流密度从2.3 A/cm^(2)线性增大至19.36 A/cm^(2)表现出了热发射性能增强效果.因此,多元稀土六硼化物La_(1–x)Sr_(x)B_(6)为一种多功能材料,在光吸收材料及热阴极材料领域具有潜在的应用前景.此外,为了揭示上述光吸收及热发射机理,采用第一性原理系统计算体等离子共振频率能量和费米能级变化规律.

The optical absorption property of the nanocrystalline La_(1–x)Sr_(x)B_(6) powder and thermionic emission property of the La_(1–x)Sr_(x)B_(6) polycrystalline bulk are investigated.As a result,the transmission wavelength of LaB6 is red-shifted from 591 nm to 658 nm with the increase of Sr doping content.The emission tests indicate that the thermionic emission current density of La_(1–x)Sr_(x)B_(6) polycrystalline bulk increases from 2.3 A/cm^(2)to 19.36 A/cm^(2)with the increase of La doping content under an applied voltage of 2000 V.The first-principle calculation results reveal that Sr doping LaB6 leads plasma frequency energy and Fermi level to decrease,resulting in the tunable characteristics of transmission wavelength and enhancement of thermionic emission.Therefore,the Sr-doped LaB6 as a multifunctional ceramic has a potential application in the field of optical filter or becomes a promising cathode for microwave device.