Microstructure And Electron Emission Performance Of RE-Mo/W Thermionic Electron Emission Materials

This research has studied the microstructure of cathode materials systematically by the means of high resolution transmission electron microscopy and scanning electron microscopy, surveyed the electron emission performance of La2O3,-Mo, La2O3-Y2O3-Mo, La2O3-Sc2C>3-Mo cathode with the self-designed electron emission surveyor and analyzed the elements changing of the surface of Mo- La2O3-Sc2C>3 cathode in-situ. while it was heated to different temperature. At last, the relationship of the microstructure of cathode, diffusion of active matter and electron emission performances has been discussed.Microstructure study shows that all the RE-Mo/W cathodes has many nanometer particles distributed in matrix crystal besides of micron meter concentrating on the crystal interface. Electron diffraction panel shows the nanometer particles are all RE oxides. So RE oxides has two form existence, one is concentrate on the matrix equiaxial crystal grain boundary as a micron particles and the other is distributed in matrix crystal dispersively as the nanometer particlesCompared the electron emission performance of Mo -La2O3, Mo- ;La2O3-Y2O3 and Mo- La2C>3-Sc2O3 cathode, the Mo- La2O3-Sc2C>3 cathode show excellent electron emission character. After surveyed, morphology of the cathodes shows restore and recrystallization. Furthermore after testing the emission characteristic, the surface crystal of the cathode has changed to more fine, and the RE oxides become more uniform on the surface. Depth profile acquired with AES has shown that excellent emission character owns to the yielding of the surplus La.Analysis the active element concentration on the Mo- La2O3-Sc2O3 cathode during it heated. Results show La and O diffuse rapidly above 1000癈, but diffusion rate of O gets slow above 1250癈, So surplus La maybe produce at this temperature. Sc shows no diffusion during heated between 800癈to 1290 癈.Analysis the result of all the experiments above, we can know porous matrix , nanometer RE oxide particles and fine crystal structure can accelerate the active matter diffusion to the surface, and do good effect to the emission performance of cathode.