The secondary electron emission properties of rare-earth-doped molybdenum emitter made by aqueous solution-solid doping method, its microstructure and surface behavior are discussed in this paper. The experimental results show that adding rare-earth oxides La2O3,Y2O3 and Gd2O3 into molybdenum raises the maximum secondary electron yield dm from 1.25 of clean Mo to 2.0-3.24 of doped molybdenum when heated to 1100-1600 8C in vacuum. With increasing percentage content of doped rare-earth oxide dm is enhanced in some extent. dm remains nearly constant during 1000h of test period when cathodes are operated at 1100 8C and under primary electron bombardment with bombarding energy of 1000 eVand bombarding power of 300W/cm2. This demonstrates such cathodes have good anti-bombing insensitivity. A work function of about 2.7-2.8 eV is obtained from Richardson lines. SEM observations and EDS analysis show that distribution of rare-earth oxides in the cathode body is inhomogeneous and tends to aggregate at molybdenum grain boundaries. By AES analysis it is found, that atomic concentrations of La and Yon the surface are about 2.5 times higher than in the bulk for a sintered body and further increase after activation.We believe the rare-earth atoms segregated at the grain boundaries diffuse along the grain boundary during the process of cathode activation. Therefore, the surface of the cathode is covered by a certain amount of rare-earth oxide. As a result, the secondary electron yield is improved.

The corrosion resistance and microstructure of anisotropic Nd-Fe-B magnet prepared byspark plasma sintering (SPS) technique were studied. The SPS Nd-Fe-B has displayed more positive corrosion potential Ecorr and lower corrosion current density Icorr than those of the conventional sintered Nd-Fe-B with the same composition in several electrolytes, indicating better anti-corrosion properties. It also shows good stability in an oxidized atmosphere. The microstructure of SPS Nd-Fe-B magnet indicates that the grain size of Nd2Fe14B is fine (about 6 mm) and uniform, and the Nd-rich phase does not form along the grain boundaries of Nd2Fe14B, but agglomerates into the triple junctions. Therefore, the pathways for corrosion propagation are restricted and the inter-granular corrosion process through Ndrich phase in the magnet is suppressed effectively. As a result, the SPS Nd-Fe-B magnet possesses excellent corrosion resistance.

Single-phase polycrystalline CoSb3 skutterudite thermoelectric compounds have been synthesized by spark plasma sintering (SPS) and the thermoelectric properties including Seebeck coefficient, electrical resistivity and thermal conductivity are measured from room temperature to 800 K. The CoSb3 compound with relative density of 97.4% and grain size of about 100 nm is achieved under the sintering condition of 873 K for 5 min, and a maximum thermoelectric dimensionless figure of merit value of 0.095 is obtained at about 673 K.