Research progress on alkaline earth aluminates for dispenser cathodes
Vacuum electron devices have wide applications in aerospace, radar communications, research equipment, and medical devices. They occupy an irreplaceable position in high-frequency, high-power microwave devices. As the most widely used electron-emitting material in vacuum electronic devices, the elec...
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Science Press
2025-04-01
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| Series: | 工程科学学报 |
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| Online Access: | http://cje.ustb.edu.cn/article/doi/10.13374/j.issn2095-9389.2024.03.08.001 |
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| author | Zichen LI Yunfei YANG Yongfeng CAI Zheng LIU Junhao SUN Hongmei LIU Wenyuan ZHOU Shizhong WEI Jinshu WANG |
| author_facet | Zichen LI Yunfei YANG Yongfeng CAI Zheng LIU Junhao SUN Hongmei LIU Wenyuan ZHOU Shizhong WEI Jinshu WANG |
| author_sort | Zichen LI |
| collection | DOAJ |
| description | Vacuum electron devices have wide applications in aerospace, radar communications, research equipment, and medical devices. They occupy an irreplaceable position in high-frequency, high-power microwave devices. As the most widely used electron-emitting material in vacuum electronic devices, the electron-emitting ability and lifetime of dispenser cathodes directly determine the device’s performance. Dispenser cathodes are mainly composed of a porous tungsten matrix and an embedded impregnant. The impregnants are indispensable components of the dispenser cathode, as they effectively improve its emission properties. An in-depth analysis and summary of the development history of impregnants is crucial for developing novel dispenser cathodes. In this paper, we review the development history, preparation methods of the impregnants, the active composition within the impregnants, the formation mechanism, and the role of the active substances in cathode performance. According to the evolution of their composition, impregnants have been classified into three types of alkaline earth metal aluminates. The first generation of impregnants is BaO–Al2O3 binary aluminates. This marks the initial application of alkaline earth metal aluminates in dispenser cathodes, providing low emission capability and establishing dispenser cathodes as an essential branch of cathode materials. The second generation of impregnants consists of BaO–CaO–Al2O3 ternary aluminates, developed by adding CaO to the first generation of impregnants. Over more than half a century, several typical impregnants have emerged, including 532 aluminates (5BaO–3CaO–2Al2O3), 411 aluminates (4BaO–1CaO–1Al2O3), and 612 aluminates (6BaO–1CaO–2Al2O3). Dispenser cathodes using second-generation impregnants exhibit excellent performance and have been extensively studied and practically applied. The third generation of multicomponent impregnants, such as scandium-containing aluminates and strontium-containing impregnants, has been developed. These are considered the most promising impregnants to meet the demands for high-frequency and high-power vacuum electronic devices due to their high emission properties. The third generation of impregnants is still at the laboratory stage owing to disadvantages such as higher melting points and poor emission uniformity. Furthermore, the electron emission properties of all current dispenser cathodes are summarized and compared, providing a valuable reference for researchers. Additionally, the importance of phase diagrams for alkaline earth metal aluminates is addressed by analyzing and summarizing the BaO–Al2O3 binary and BaO–CaO–Al2O3 ternary phase diagrams. Data on the structure of various impregnants and the phase diagrams of binary and ternary alkaline earth metal aluminates clarify the contribution of different impregnants to cathode performance. Finally, an outlook on the development of alkaline earth aluminates for dispenser cathodes is presented, including crystal structure analysis, stability adjustments, and preparation process optimization. |
| format | Article |
| id | doaj-art-b4ed3471013c4d818e9f997d79d76289 |
| institution | OA Journals |
| issn | 2095-9389 |
| language | zho |
| publishDate | 2025-04-01 |
| publisher | Science Press |
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| series | 工程科学学报 |
| spelling | doaj-art-b4ed3471013c4d818e9f997d79d762892025-08-20T02:17:01ZzhoScience Press工程科学学报2095-93892025-04-0147473975210.13374/j.issn2095-9389.2024.03.08.001240308-0001Research progress on alkaline earth aluminates for dispenser cathodesZichen LI0Yunfei YANG1Yongfeng CAI2Zheng LIU3Junhao SUN4Hongmei LIU5Wenyuan ZHOU6Shizhong WEI7Jinshu WANG8School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaSchool of Materials Science and Engineering, Henan University of Science and Technology, Henan 471023, ChinaSchool of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, ChinaVacuum electron devices have wide applications in aerospace, radar communications, research equipment, and medical devices. They occupy an irreplaceable position in high-frequency, high-power microwave devices. As the most widely used electron-emitting material in vacuum electronic devices, the electron-emitting ability and lifetime of dispenser cathodes directly determine the device’s performance. Dispenser cathodes are mainly composed of a porous tungsten matrix and an embedded impregnant. The impregnants are indispensable components of the dispenser cathode, as they effectively improve its emission properties. An in-depth analysis and summary of the development history of impregnants is crucial for developing novel dispenser cathodes. In this paper, we review the development history, preparation methods of the impregnants, the active composition within the impregnants, the formation mechanism, and the role of the active substances in cathode performance. According to the evolution of their composition, impregnants have been classified into three types of alkaline earth metal aluminates. The first generation of impregnants is BaO–Al2O3 binary aluminates. This marks the initial application of alkaline earth metal aluminates in dispenser cathodes, providing low emission capability and establishing dispenser cathodes as an essential branch of cathode materials. The second generation of impregnants consists of BaO–CaO–Al2O3 ternary aluminates, developed by adding CaO to the first generation of impregnants. Over more than half a century, several typical impregnants have emerged, including 532 aluminates (5BaO–3CaO–2Al2O3), 411 aluminates (4BaO–1CaO–1Al2O3), and 612 aluminates (6BaO–1CaO–2Al2O3). Dispenser cathodes using second-generation impregnants exhibit excellent performance and have been extensively studied and practically applied. The third generation of multicomponent impregnants, such as scandium-containing aluminates and strontium-containing impregnants, has been developed. These are considered the most promising impregnants to meet the demands for high-frequency and high-power vacuum electronic devices due to their high emission properties. The third generation of impregnants is still at the laboratory stage owing to disadvantages such as higher melting points and poor emission uniformity. Furthermore, the electron emission properties of all current dispenser cathodes are summarized and compared, providing a valuable reference for researchers. Additionally, the importance of phase diagrams for alkaline earth metal aluminates is addressed by analyzing and summarizing the BaO–Al2O3 binary and BaO–CaO–Al2O3 ternary phase diagrams. Data on the structure of various impregnants and the phase diagrams of binary and ternary alkaline earth metal aluminates clarify the contribution of different impregnants to cathode performance. Finally, an outlook on the development of alkaline earth aluminates for dispenser cathodes is presented, including crystal structure analysis, stability adjustments, and preparation process optimization.http://cje.ustb.edu.cn/article/doi/10.13374/j.issn2095-9389.2024.03.08.001dispenser cathodealkaline earth metal aluminateimpregnantreaction mechanismelectron emission |
| spellingShingle | Zichen LI Yunfei YANG Yongfeng CAI Zheng LIU Junhao SUN Hongmei LIU Wenyuan ZHOU Shizhong WEI Jinshu WANG Research progress on alkaline earth aluminates for dispenser cathodes 工程科学学报 dispenser cathode alkaline earth metal aluminate impregnant reaction mechanism electron emission |
| title | Research progress on alkaline earth aluminates for dispenser cathodes |
| title_full | Research progress on alkaline earth aluminates for dispenser cathodes |
| title_fullStr | Research progress on alkaline earth aluminates for dispenser cathodes |
| title_full_unstemmed | Research progress on alkaline earth aluminates for dispenser cathodes |
| title_short | Research progress on alkaline earth aluminates for dispenser cathodes |
| title_sort | research progress on alkaline earth aluminates for dispenser cathodes |
| topic | dispenser cathode alkaline earth metal aluminate impregnant reaction mechanism electron emission |
| url | http://cje.ustb.edu.cn/article/doi/10.13374/j.issn2095-9389.2024.03.08.001 |
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