Electrostatic adhesion processes are used in preparing composite aerosol particles with the electrostatic adhesion force acting between electropositively-charged and electronegatively-charged particles. This process enables one to disperse the core and subcomponent particles more uniformly and to control the amounts of subcomponent particles adhered to the surface of individual core particles by adjusting the charging voltage. Using the composite particles prepared by the electrostatic adhesion process as a starting powder for sintering, a composite bulk body of the Ba2YCu3O7-X oxide superconductor with BaZrO3 inclusions is produced. BaZrO3 particles with diameters less than 100 nm are uniformly dispersed in the Ba2YCu3O7-X matrix. The composite bulk body shows improvement in critical current density, which is based on the uniform dispersion of fine BaZrO3 particles as magnetic flux pinning centers. These advantages are attributed to the uniform dispersion of BaZrO3 over the whole starting powder.