(Pb, La)(Zr, Ti)O₃ (PLZT) with antiferroelectric properties can be applied as a capacitor whose capacitance increases in a high electric field. From this, we obtained a high sintering density at 950 °C by adding low-temperature sintering additives, 8.0 wt% of PbO and 2.5 wt% of ZnO, simultaneously to a (Pb_0.88, La_0.12)(Zr_0.86, Ti_0.14)O₃ composition. The change in electrical characteristics was confirmed in terms of Sn⁴⁺ substitution, resulting in no change in the sintering density by Sn⁴⁺ substitution. However, as the amount of Sn⁴⁺ substitution increases, the dielectric constant gradually decreases from 1300 to 700, and the grain size decreases from about 4 to 1 µm in terms of microstructure. In the crystal structure analysis, the general formation of a single perovskite structure was confirmed. The results of the hysteresis curve measurement revealed that the breakdown electric field increases from 4 to 9 kV·mm⁻¹ as the amount of Sn⁴⁺ substitution gradually increases. However, polarization decreases in the same way as the permittivity trend. The composition exhibits excellent electrical properties when the ratio of Sn⁴⁺ is 0.4: a high energy storage density of 3.5 J·cm⁻³, energy efficiency of 80%, and breakdown electric field of about 8.5 kV·mm⁻¹.