I learn some basic information about the relative permittivity. I can understand that when the relative permittivity $\epsilon_r \to \infty$ that material is a perfect conductor. On the other hand, for any finite value of $\epsilon_r$, that material is a perfect dielectric.
However, I need help to obtain an intuitional or qualitative understanding of a specific physical setting, that is, two-layer different materials, a dielectric (diel_A) and a vacuum, between two plates (electrodes) with a fixed external electric field. In this case, what is the actual physical effect, or what happens if the relative permittivity of "diel_A" increases? Thank you in advance!