In this paper, a possibility of use of the controlled decomposition of solid solutions of oxides with perovskite structure in the state of coexisting domains of the antiferroelectric (AFE) and ferroelectric (FE) phases for manufacturing materials with the negative refractive index is demonstrated. The lead zirconate titanate-based solid solutions are considered as an example of substances suitable for creation of such materials. Manufactured composites constitute a dielectric AFE matrix with a structure of conducting interphase boundaries separating domains of the FE and AFE phases. The electric conductivity of the interphase boundaries occurs as a result of the local decomposition of the solid solutions in the vicinity of these boundaries. The decomposition process and consequently the conductivity of the interphase boundaries can be controlled by means of external influences.