Secondary Electron Emission Characteristic of Insulated Al_2O_3 Ceramics with Cr_2O_3 Coating

Cr2O3 coatings were applied to α-Al2O3 insulators and followed by heat treatment in special conditions. Secondary electron emission coefficient, SEM, XRD, XPS and EELS of the samples were measured and observed. During heat treatment, new phases can be formed, because the coatings can penetrate the surfaces of the insulators and mix with α-Al2O3. The experimental results of XPS and EELS show that due to the energy gaps of the surfaces decreasing, the densities of defect state, impurity state and surface state in the energy gaps increasing, more recombination centers and trapping centers can be formed, and that is favorable for the transition of non-equilibrium carriers and leading the decrease of secondaty electron emission.