{"title":"Enhanced thermionic electron emission of (La1-x-yPrxBay)B6 cathode transforming from the grain boundary to the grain","authors":"Xinyu Yang, Yulin Song, Zimeng Li, Biao Cai, Cunchao Dong, Chenhui Deng, Yan Wang, Jianing Zhang, Wenpeng Xiang, Jiuxing Zhang","doi":"10.1111/jace.20373","DOIUrl":null,"url":null,"abstract":"<p>The mixed rare earth/alkali earth was initially employed to enhance the thermionic emission performance of lanthanum hexaboride (LaB<sub>6</sub>) through forming the high-dense (La<sub>1-x-y</sub>Pr<sub>x</sub>Ba<sub>y</sub>)B<sub>6</sub> polycrystal by spark plasma sintering (SPS). La<sub>0.6</sub>Pr<sub>0.3</sub>Ba<sub>0.1</sub>B<sub>6</sub> exhibits the highest current density in space charge limited (SCL) region at T = 1873K while La<sub>0.5</sub>Ba<sub>0.5</sub>B<sub>6</sub> has the highest current density in temperature limited (TL) region. The maximum current density of 14.07 A/cm<sup>2</sup> at T = 1673K for La<sub>0.5</sub>Ba<sub>0.5</sub>B<sub>6</sub> is higher than that of 11.71 A/cm<sup>2</sup> at T = 1873K for LaB<sub>6</sub> polycrystal, presenting superior emission characteristics at the low temperature, mainly ascribed to the contribution of the Ba element. With the increase in the Ba content, the location of the highest electron emission shifts from the grain boundary (in La<sub>0.5</sub>Pr<sub>0.5</sub>B<sub>6</sub> and La<sub>0.6</sub>Pr<sub>0.3</sub>Ba<sub>0.1</sub>B<sub>6</sub>) to the internal grain (in La<sub>0.6</sub>Pr<sub>0.1</sub>Ba<sub>0.3</sub>B<sub>6</sub> and La<sub>0.5</sub>Ba<sub>0.5</sub>B<sub>6</sub>). The consumption rate of the elements during thermionic emission follows the order: Ba > Pr > La. The experimental data on the current density aligns closely with the theoretical predictions, demonstrating the emission of (La<sub>1-x-y</sub>Pr<sub>x</sub>Ba<sub>y</sub>)B<sub>6</sub> ceramic obeys classical thermionic emission mechanism of metals.</p>","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":"108 5","pages":""},"PeriodicalIF":3.5000,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the American Ceramic Society","FirstCategoryId":"88","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/jace.20373","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, CERAMICS","Score":null,"Total":0}
引用次数: 0
摘要
通过火花等离子烧结（SPS）形成高密度（La1-x-yPrxBay）B6 多晶体，最初采用稀土/碱土混合物来提高六硼化铋镧（LaB6）的热离子发射性能。在 T = 1873K 时，La0.6Pr0.3Ba0.1B6 在空间电荷受限（SCL）区域显示出最高的电流密度，而 La0.5Ba0.5B6 在温度受限（TL）区域显示出最高的电流密度。在 T = 1673K 时，La0.5Ba0.5B6 的最大电流密度为 14.07 A/cm2，高于 LaB6 多晶在 T = 1873K 时的 11.71 A/cm2，在低温下呈现出更优越的发射特性，这主要归功于 Ba 元素的贡献。随着钡元素含量的增加，电子发射率最高的位置从晶界（La0.5Pr0.5B6 和 La0.6Pr0.3Ba0.1B6）转移到晶粒内部（La0.6Pr0.1Ba0.3B6 和 La0.5Ba0.5B6）。在热电子发射过程中，元素的消耗率按照以下顺序进行： Ba > Pr > La。电流密度的实验数据与理论预测结果非常吻合，证明 (La1-x-yPrxBay)B6 陶瓷的发射符合经典的金属热离子发射机制。
Enhanced thermionic electron emission of (La1-x-yPrxBay)B6 cathode transforming from the grain boundary to the grain
The mixed rare earth/alkali earth was initially employed to enhance the thermionic emission performance of lanthanum hexaboride (LaB6) through forming the high-dense (La1-x-yPrxBay)B6 polycrystal by spark plasma sintering (SPS). La0.6Pr0.3Ba0.1B6 exhibits the highest current density in space charge limited (SCL) region at T = 1873K while La0.5Ba0.5B6 has the highest current density in temperature limited (TL) region. The maximum current density of 14.07 A/cm2 at T = 1673K for La0.5Ba0.5B6 is higher than that of 11.71 A/cm2 at T = 1873K for LaB6 polycrystal, presenting superior emission characteristics at the low temperature, mainly ascribed to the contribution of the Ba element. With the increase in the Ba content, the location of the highest electron emission shifts from the grain boundary (in La0.5Pr0.5B6 and La0.6Pr0.3Ba0.1B6) to the internal grain (in La0.6Pr0.1Ba0.3B6 and La0.5Ba0.5B6). The consumption rate of the elements during thermionic emission follows the order: Ba > Pr > La. The experimental data on the current density aligns closely with the theoretical predictions, demonstrating the emission of (La1-x-yPrxBay)B6 ceramic obeys classical thermionic emission mechanism of metals.
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The Journal of the American Ceramic Society contains records of original research that provide insight into or describe the science of ceramic and glass materials and composites based on ceramics and glasses. These papers include reports on discovery, characterization, and analysis of new inorganic, non-metallic materials; synthesis methods; phase relationships; processing approaches; microstructure-property relationships; and functionalities. Of great interest are works that support understanding founded on fundamental principles using experimental, theoretical, or computational methods or combinations of those approaches. All the published papers must be of enduring value and relevant to the science of ceramics and glasses or composites based on those materials.
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