Secondary electron emission from a cathode material in AC PDP (Plasma Display Panel) is dominated by potential emission mechanism, which is sensitive to band structure of a protective layer. Therefore, the secondary electron emission property can be modified by a change in the energy band structure of the protective layer. Mg2-2xTixO2 films were prepared by e-beam evaporation method to be used as possible substitutes for the conventional MgO protective layer. The oxygen content in the films and in turn, the ratio of metal to oxygen gradually increased with the increasing TiO2 content in the starting materials. The pure MgO films exhibited the crystallinity with strong (111) orientation. The Mg2-2xTixO2 films, however, had the crystallinity with (311) preferred orientation. The stress relaxation, when the [TiO2/(MgO+TiO2)] ratio in the evaporation starting materials was 0.15, seems to be related to inhomogeneous film surface due to an excessive addition of TiO2 to MgO. When the [TiO2/(MgO+TiO2)] ratios of 0.1 and 0.15 were used, the deposited films exhibited the secondary electron emission yields improved by 50% compared to that of the conventional MgO protective layer, which resulted in reduction in discharge voltage by 12%.