To further explore the material early-warning application of the luminescent coating,we demonstrated a new method by preparing a mixture layer of metallic erbium and oxidized zirconium（Er-ZrO2 layer） using the double glow plasma surface alloying technology with Zr and Er co-sputtering under oxygen plasma exposure.The microstructure,composition and luminescence properties of the layers were characterized by scanning electron microscopy,X-ray diffraction,Raman and photoluminescence spectra.The dependence of the luminescence on the gradual concentration was studied.Results indicated that the contents of Zr,Er and O in the layer decreased gradually along the depth direction.The luminescence properties were concentration-dependent.X-ray diffraction analysis showed that the crystalline structure of ZrO2 layer transferred from a mixture phase of tetragonal and monoclinic to pure monoclinic phase with the Zr-Er co-sputtering.The Raman bands of the layers depended on its local ZrO2 crystal structures.Photoluminescence characteristics of Er-ZrO2 layer revealed that the main emission bands were assigned to 2H11/2→4I15/2 and 4S3/2→4I15/2 transition under the excitation at 325 nm.The fact suggested that the plasma surface alloying is an effective method to obtain luminescent layer.
Based on a simple classical model specifying that the primary electrons interact with the electrons of a lattice through the Coulomb force and a conclusion that the lattice scattering can be ignored, the formula for the average energy required to produce a secondary electron (ε) is obtained. On the basis of the energy band of an insulator and the formula for ε, the formula for the average energy required to produce a secondary electron in an insulator (εi) is deduced as a function of the width of the forbidden band (Eg) and electron affinity χ. Experimental values and the εi values calculated with the formula are compared, and the results validate the theory that explains the relationships among Eg , χ, and εi and suggest that the formula for εi is universal on the condition that the primary electrons at any energy hit the insulator.
