Abstract: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 (δmax) was monitored at regular intervals. After the experiment, the cathode was analyzed with SEM, EDS and XRD techniques. The results show thatδmaxof multi-RE₂O₃-Mo cermets cathode heated to 1 100℃under electron bombardment of 300 W/cm²reaches the peak of 3.35 at 200 h. After 500 h of bombardment, the maximum secondary-electron-yield curve stabilizes. Theδmaxvalue of the cathode remains at about 2.5 after 1 000 h and represents a good anti-bombardment property. The highδmaxvalue of the cathode is related with formation of an enriched Y₂O₃layer on the surface under high temperature and with the amount ofLa₂O₃ particles in the shape of nanometer distributed on the surface. Under the experimental conditions, the drop ofδmax value may be caused by the reduction of La₂O₃content and the porous layer resulted from evaporation of MoO₂, which is formed when Mo at the surface is oxidized.

Key words: rare earth oxide; molybdenum; anti-electron-bombardment property; secondary emission