Durability experiment on anti-electron-bombardment of RE_2O_3-Mo secondary emission material

A durability test to determine anti-bombardment sensitivity of multi-RE2O3-Mo secondary emission material was carried out and the variation of maximum secondary emission coefficient （δ）max)) was monitored at regular intervals. After the experiment, the cathode was analyzed with SEM, EDS and XRD techniques. The results show that δ)max) of multi-RE2O3-Mo cermets cathode heated to 1 100 ℃ under electron bombardment of 300 W/cm2 reaches the peak of 3.35 at 200 h. After 500 h of bombardment, the maximum secondary-electron-yield curve stabilizes. The δ)max) value of the cathode remains at about 2.5 after 1 000 h and represents a good anti-bombardment property. The high δ)max) value of the cathode is related with formation of an enriched Y2O3 layer on the surface under high temperature and with the amount of La2O3 particles in the shape of nanometer distributed on the surface. Under the experimental conditions, the drop of δ)max) value may be caused by the reduction of La2O3 content and the porous layer resulted from evaporation of MoO2, which is formed when Mo at the surface is oxidized.