“Discharge delay” and “dependence of discharge delay on temperatures” are solved by improving a protective layer, thus a PDP can be driven at a low voltage. Furthermore, the PDP can display excellent images by suppressing “dependence of discharge delay on space charges.” Liquid-phase magnesium alkoxide (Mg(OR)2) or acetylacetone magnesium ate whose purity is 99.95% or more is prepared, and is hydrolyzed by adding a small amount of acids to the solution. Thus, a gel of magnesium hydroxide that is a magnesium oxide precursor is formed. Burning the gel in atmosphere at 700° C. or more produces powder containing MgO particles 16a-16d having the NaCl crystal structure with (100) and (111) crystal faces or with (100), (110) and (111) crystal faces. By pasting the powder on a dielectric layer 7 or a surface layer 8, the MgO powder 16 is formed so as to serve as the protective layer.