单晶La0.2Ce0.8B6的制备、表征及热发射性能研究

Fabrication,characterization and thermionic emission properties of La_(0.2)Ce_(0.8)B_6 single crystal

采用区域熔炼法制备了大尺寸、高质量多元稀土六硼化物La_(0.2)Ce_(0.8)B_6单晶体。结合X射线劳埃定向法对(110)和(310)晶面进行了定向,并系统研究了热发射性能。结果表明,当阴极温度为1 673,1 773和1 873K时(110)和(310)晶面最大电流密度分别为3.60,7.73,12.44A/cm^2和3.25,11.67,16.93A/cm^2。表明晶面间发射性能存在"各向异性"的特点。不同发射温度下的(110)和(310)晶面平均有效逸出功分别为2.85和2.80eV,表明单晶La_(0.2)Ce_(0.8)B_6具有良好的热发射性能。

The multiple rare-earth hexaboride La0.2Ce0.8B6 single crystal with large size and high quality has been fabricated by the floating zone method.The(110)and(310)crystal surfaces of La0.2Ce0.8B6 are oriented by the X-ray Laue diffraction method and their thermionic emissions properties are measured.The results show that the maximum emission current densities of the(110)and(310)crystal surfaces at 1 673,1 773 and 1 873 K are 3.60,7.73,12.44 A/cm 2 and 3.25,11.67,16.93 A/cm 2,respectively.It means that the thermionic emission is strongly anisotropic for the different crystal surfaces.The average value of effective work functions of(110)and(310)crystal surfaces at different temperatures are calculated to be 2.85 eV and 2.80 eV,indicating an excellent thermionic emission properties of La0.2Ce0.8B6 single crystal.