Multilayer ceramic capacitors based on relaxor BaTiO₃-Bi(Zn_1/2Ti_1/2)O₃ for temperature stable and high energy density capacitor applications

The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayer ceramic capacitors based on relaxor BaTiO₃-Bi(Zn_1/2Ti_1/2)O₃ (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ->-1 GΩ-cm at 300-°C), and negligible saturation up to fields as high as 150-kV/cm. Multilayer capacitor embodiments were fabricated and found to exhibit similar dielectric and resistivity properties. The energy density for the multilayer ceramics reached values of ∼2.8-J/cm³ at room temperature at an applied electric field of ∼330-kV/cm. This represents a significant improvement compared to commercially available multilayer capacitors. The dielectric properties were also found to be stable over a wide range of temperatures with a temperature coefficient of approximately -2000-ppm/K measured from 50 to 350-°C, an important criteria for high temperature applications. Finally, the compatibility of inexpensive Ag-Pd electrodes with these ceramics was also demonstrated, which can have implications on minimizing the device cost.