悬浮区域熔炼法制备Ce1-xPrxB6单晶体及其热发射性能研究

以CeB₆和PrB₆粉末为原料, 采用放电等离子烧结结合悬浮区域熔炼法成功制备了晶体质量良好的多元稀土六硼化物Ce_1-xPr_xB₆(x=0.1、0.2、0.4)单晶体, 并系统研究了该系列单晶体(100)晶面热电子发射性能。结果表明: Ce_0.8Pr_0.2B₆单晶(100)晶面具有最好的热发射性能, 在1873 K, 最大电流发射密度达到66.07 A/cm², 比CeB₆单晶的电流发射密度提高约20%。此外, Ce_0.9Pr_0.1B₆、Ce_0.6Pr_0.4B₆单晶(100)晶面的热发射电流密度分别为65.81 A/cm²和65.31 A/cm²。Ce_0.8Pr_0.2B₆单晶(100)晶面的逸出功最低, 为2.61 eV, 其它单晶(100)晶面的逸出功在2.64~2.753 eV范围内。因此, Ce_1-xPr_xB₆多元稀土六硼化物单晶具有良好的发射性能和低的逸出功, 作为热阴极材料有很好的应用前景。

Synthesis and Properties of Single Crystal Ce1-xPrxB6 by Floating Zone Melting

High-quality single crystals Ce_1-xPr_xB₆ (x = 0.1, 0.2, 0.4) hexaborides were successfully prepared by the reactive spark plasma sintering (SPS) combining with the floating zone melting method using powder of CeB₆ and PrB₆ as raw materials. The thermionic emission properties of the (100) plane of single crystals were investigated. Results show that the (100) plane of Ce_0.8Pr_0.2B₆ single crystal has the maximum emission current density, 66.07 A/cm² at 1873 K, which is higher than the current reported CeB₆ single crystal, increased by about 20%. In addition, the thermal emission current density of (100) plane of Ce_0.9Pr_0.1B₆, Ce_0.6Pr_0.4B₆ single crystals are 65.81 A/cm² and 65.31 A/cm², respectively. The (100) plane of Ce_0.8Pr_0.2B₆ single crystal has the lowest work function of 2.61 eV, while the work functions of other single crystals are in the range of 2.64-2.753 eV. Therefore, single crystals Ce_1-xPr_xB₆ hexaborides have good thermionic emission and low work function, which promises good prospects in the application as a hot cathode material.