ASTUDY OF VALENCE OF YTTRIUM IN Y_2O_3 Mo CATHODE

The valenceofelementyttrium of Y2 O3 Mocathode materialhasbeenstudied by usingther mal weight analysis, X ray diffraction analysis, Scanning electron microscopy and X rayphotoelectronspectrum . It hasbeen provedthatyttrium oxidecan bereduced by molybdenum carbide. Thereaction between powdered Y2 O3 and Mo2 Ccan happen at 1173 , and Y2 O3may bereduced to metallicyttrium . Afterthepowder mixtureof Y2 O3 and Mo2 Cwasheat treated at1873 K, Yttrium existsin two kinds of chemicalstate- yttrium of zero valence and yttrium ofthreevalences.

Emission mechanism of Mo-Y_2O_3 cathode

The valence of element yttrium of Y 2O 3 Mo cathode material was studied by thermal analysis, X ray diffraction analysis, scanning electron microscopy and X ray photoelectron spectra, and the emission mechanism of Mo Y 2O 3 cathode was discussed. It was proved that reaction between powder Y 2O 3 and Mo 2C can happen at 1 173 K, and Y 2O 3 be reduced to metallic yttrium. After the powder mixture of Y 2O 3 and Mo 2C is heat treated at 1 873 K, yttrium exists in two kinds of state—yttrium of zero valence and yttrium of three valences. The formation of monoatomic layer of metallic yttrium at the surface of filament is the cause of emissivity of the cathode. Yttrium at the surface doesn’t provide emission current, but the momoatomic active surface layer has a lower work function than clean molybdenum. [

Mo-Y_2O_3阴极发射机理研究

采用热重分析、X射线衍射、扫描电镜及光电子能谱等方法对Mo Y2 O3阴极中钇的价态进行了研究 ,探讨了该阴极的发射机理。Y2 O3与Mo2 C在 1173K以上发生化学反应。Y2 O3与Mo2 C混合物经 1873K高温处理后 ,产物中含有两种价态的Y :Y0 和化合态的Y3+。Mo Y2 O3阴极的发射可用原子膜机理解释 ;在阴极工作过程中 ,Mo2 C将Y2 O3还原成单质钇 ,钇覆盖在钼基体表面 ,降低了基体钼的逸出功 ,促进了阴极的发射。