Dielectrics are materials with dielectric polarization and paraelectricity, and exhibit various properties depending on external field, stress, and heat. Among them, ferroelectrics are materials in which the direction of spontaneous polarization is reversed by an electric field. Ferroelectrics undergo a structural phase transition at a certain temperature due to a change in the symmetry of the crystal structure. Ferroelectric phase transitions are classified according to changes in the physical properties that characterize the ferroelectric material with respect to temperature. In this paper, we measure the crystal structure and dielectric properties of ferroelectrics undergoing a second-order structural phase transition and explain the experimental results using phenomenology.