Figure 19: Temperature dependence of capacity C = 𝜖 0 𝜖 r A/d (A is electrode area and d thickness of dielectric) of thin film capacitors, measured with 50 mV AC amplitude at 1 kHz and zero DC-bias. The dielectric was Ba0.6Sr0.4TiO3 (BSTO-0.6, black line), BSTO-0.8 (green), and BTO (red). With decreasing Ba substitution, the ferroelectric Curie temperature (maximum of 𝜖 r ) increases. This structural phase transition is remarkably broadened due to the thin film nature of the dielectric. For C = 1 0 0  nF, d = 1 μm, and 3 mm circular electrodes, the relative permittivity 𝜖 r of the dielectric is above 1,600.