Pr_(1-x)Ce_xB_6阴极材料的原位反应合成及性能研究

Synthesis and properties of multiple boride Pr_(1-x)Ce_xB_6 cathodes by reactive spark plasma sintering

本文以CeH2,PrH2纳米粉和B粉为原料,在无氧环境下采用放电等离子原位反应成功制备了单相多元稀土六硼化物Pr1-xCexB6(x=0.2—0.8)阴极材料.系统研究了掺杂元素Ce对Pr1-xCexB6的物相组成、力学性能及热电子发射性能的影响.结果表明,当烧结温度为1450C,烧结压强为50MPa时可制得单相的Pr1-xCexB6多晶块体材料并且该系列样品具有良好的力学性能,维氏硬度和抗弯强度最高值分别达到了24.34GPa和226.02MPa,已达到单晶水平.热电子发射性能结果表明,随着Ce掺杂量的增加Pr1-xCexB6的发射电流密度线性增加.当阴极温度为1973K,外加电压为950V时,Pr0.4Ce0.6B6最大发射电流密度达到47.3A·cm2,该值远高于传统热压烧结法制备的发射电流密度.因此,本文该方法制备的Pr1-xCexB6多晶块体具有良好的力学性能和发射性能,作为热阴极材料将会有很好的应用前景.

The polycrystalline Pr1-xCexB6（x = 0.2, 0.4, 0.6, 0.8） hexaborides are prepared by the reactive spark plasma sintering （SPS） method using mixed powder of Cell2, PrH2 and B. The effects of Ce doping on the phase composition, the mechanical properties and the thermionic emission properties of the hexaboride are investigated. The single-phased hexaborides Pr1-xCexB6 bulks are sintered at a temperature of 1450℃, pressure of 50MPa and holding time of 5 min, and the sintered samples show high value of Vickers hardness （24.34 GPa） and bend strength （226.02 MPa）. The thermionic emission results show that with the increase of Ce content, the thermionic emission current density increases linearly and the maximum value of Pr0.4Ce0.6B6 reaches 47.3 A.cm-2 under an applied voltage of 950 V at 1973 K, which is much higher than that obtained by traditional method. Thus, the SPS technique represents a suitable method to synthesize the dense rare-earth hexaborides with excellent properties.