I thought the same thing would be the case, the only way to make use of it is to have a solid body of any given dielectric material otherwise its of no use. I read that low dielectric constant resins can perform as a high dielectric if they have some of the high dielectric inside the resin but its not the case.Do you mean epoxy resin filled with barium titanate powder? What should it be good for? The ceramic has extremely high permittivity, causing inhomogenous field distribution and promote dielectric breakdown in the surrounding low permittivity isolators.
You are right. The particle boundaries will experience a large field and can cause breakdown. Homogeneous materials will be the preferred choice. Even some inert gas at high pressure will provide a good insulation. But why BaTiO3? Why not Al2O3 or SiO2 filled resins?if they have some of the high dielectric inside the resin but its not the case.