磁控管用新型直热式稀土铪酸钆陶瓷阴极研究

为了提高大功率磁控管的输出功率，延长其使用寿命，采用难熔稀土氧化钆和过渡金属氧化铪制备大功率磁控管用新型直热式稀土铪酸钆陶瓷阴极，并对该阴极的热发射特性和寿命特性等进行了测试，热发射测试结果显示该阴极在1300℃ br即可提供0.1A/cm²发射电流密度，1600℃ br下可提供超过1.93A/cm²的发射电流密度.寿命实验结果显示，该阴极在1500℃ br，直流负载为0.5A/cm²的条件下，寿命已经超过4000h.最后，利用X射线衍射仪、扫描电镜、能谱分析仪、氩离子深度刻蚀俄歇电镜等设备分别对该阴极活性物质的分子结构，阴极表面微观形貌、元素成分及含量等进行了分析.结果表明，高温烧结合成了单一的铪酸钆物相，烧结过程中当一种Gd³⁺价稀土氧化钆掺入Hf⁴⁺价的过渡金属氧化铪时，会发生离子置换固溶，为了保持铪酸钆晶格的电中性，晶格中就会产生一个氧空位.当阴极在激活、老练、热发射测试时，会加速氧空位的生成，产生的氧空位越多，阴极表面导电性就会越好，这间接降低了逸出功，从而提高了阴极的热发射能力.

A Novel Direct-Heated Rare-Earth Gd2Hf2O7 Ceramic Cathode Applied in Magnetron

In order to enhance the output power,prolong the lifetime of the high power magnetron,a method of refractory rare-earth oxide Gd₂O₃ doped transition metal oxide HfO₂ was used to prepare direct-heated rare-earth Gd₂Hf₂O₇ ceramic cathode.The thermionic emission and life characteristics of the Gd₂Hf₂O₇ cathode had been measured.The results show that the cathode can provide 0.1A/cm² current density for the space charge limitation at 1300℃br,more than 1.93A/cm² at 1600℃br under 300V anode voltage.The lifetime for the cathode is more than 4000 h with an initial load of 0.5A/cm² at 1500℃br.Finally,the molecular structure,surface microstructure,element composition and content of the Gd₂Hf₂O₇ ceramic cathode had been analyzed by the XRD,SEM,EDS,AES(equipped with argon ion etching in-depth analysis) respectively.The analysis results show that the single Gd₂Hf₂O₇ phase has formed in the high sintering temperature.When the Gd³⁺ valences Gd₂O₃ doped the Hf⁴⁺ valences HfO₂,the substitutional solid solution will be formed.In order to maintain the electrical neutrality of the Gd₂Hf₂O₇ lattice,an oxygen vacancy will be generated in the lattice.During the cathode activating,aging,and thermally testing,the oxygen vacancy will be generated fast.The more oxygen vacancies are obtained,the better the conductivity of the cathode surface has.Besides,the work function of the cathode can also be reduced due to the improvement of the electro-conductivity that enhances the thermionic emission capability of the cathode.