稀土难熔金属阴极材料的研究进展

Advance in Rare Earth Doped Refractory Metal Cathode Materials

介绍了3种阴极,镧钼阴极、稀土钼金属陶瓷阴极及钪钨基扩散阴极的制备方法及发射性能。针对电子管用镧钼阴极发射不稳定的问题,采用原位光电子能谱法研究高温下La2O3(4%,质量分数)-Mo阴极表面La的价态,确定了适合La2O3-Mo阴极的碳化、激活等关键工艺制度,使实用型La2O3-Mo电子管的使用寿命超过了应用要求的水平。为满足大功率磁控管的发展要求,研究了新型稀土钼金属陶瓷阴极。经过高温激活处理后,材料的最大次级发射系数达5.24,实用管型测试结果表明,稀土钼金属陶瓷阴极的性能优于钡钨阴极,显示了良好的应用前景。亚微米结构的钪钨基扩散阴极具有优异的热发射性能,850℃下阴极的发射电流密度可达42A/cm2,激活后Ba,Sc,O等元素形成的活性多层,均匀覆盖在阴极表面,促进了阴极的发射。

Preparation method and emission properties of three kinds of cathode, that is, lanthanated molybdenum cathode, RE2O3 - Mo cermet cathode and scandia doped tungsten matrix dispenser cathode, were introduced. The chemical state of lanthanum on the surface of La2O3 （4% , mass fraction） - Mo cathode was studied by in - situ XPS under high temperatures. The optimum technological parameters for carbonization process, which is a key procedure for preparation of La2O3 - Mo cathodes, were determined based on the experimental results. By applying the new technological parameters, the lifetime of the cathode was improved, exceeding that required for practical use. In order to meet the requirement of high output power magnetrons, novel RE2O3 - Mo cermet cathodes were developed. After activation, the maximum secondary emission yield could get to 5.24. Magnetron equipped with RE203 - Mo cermet cathode exhibits output power higher than that equipped with Ba - W cathode, indicating a prospective application of the former one. Sc2O3 - W matrix dispenser cathode exhibits excellent emission property. The emission current density could reach 42A/cm^2 at 850℃. It is found that a uniform multilayer composed of Ba, Sc, and O activated on the cathode surface leads to its conspicuous emission performance.