Abstract: 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
deerease of secondaty electron emission.

Key words: Cr₂O₃ coating, α-Al₂O₃ insulator, secondary electron emission characteristic