Single layer air co-fired capacitors with Pt internal electrodes were prototyped for the compositions 0.8CaTiO 3 -0.2CaHfO 3 (CHT) and 0.5 mol% Mn-doped 0.8CaTiO 3 -0.2CaHfO 3 (CHT + Mn) to yield a material with a room-temperature relative permittivity of e r~1 70, thermal coefficient of capacitance (TCC) of ±15.8% to ±16.4% from À50°C to 150°C, and a band gap of~4.0 eV. Impedance spectroscopy revealed that doping with Mn reduces both the ionic and electronic conductivity. Undoped CHT single layer capacitors exhibited ambient energy densities as large as 9.0 J/cm 3 , but showed a drastic decrease in energy density above 100°C. When doped with 0.5 mol% Mn, the temperature dependence of the breakdown strength was minimized, and energy densities similar to ambient values (9.5 J/cm 3 ) were observed up to 200°C. At 300°C, energy densities as large as 6.5 J/cm 3 were measured. The design rationale for these dielectrics centered on materials with large band gaps, linear or weakly nonlinear permittivities, and high breakdown strengths. These observations suggest that with further reductions in grain size and dielectric layer thickness, the CaTiO 3 -CaHfO 3 system is a strong candidate for integration into future power electronics applications.

Microstructural control in thin-layer multilayer ceramic capacitors (MLCCs) is one of the present day challenges for increasing capacitive volumetric efficiency and high voltage dielectric properties. The present paper continues a series of investigations aimed at engineering the stability of ultra-thin Ni layers in basemetal electrode MLCCs. A kinetic approach based on the control of sintering profiles is found to not only prevent Ni electrode discontinuities, but also to significantly improve the interfacial electrical properties. Increasing sintering heating rates from 200 to 30001C/h leads to a decrease in its temperature dependence of capacitance. Faster heating rates also reduce the BaTiO 3 grain size, which is beneficial to the reliability of multilayer capacitors. A direct correlation between heating rates, the thickness of an interfacial (Ni, Ba, and Ti) alloy reaction layer and the interfacial contact resistance has been observed. The decrease in the alloy layer thickness at high heating rates leads to an increased effective Schottky barrier height between the dielectric and electrode toward its theoretical value of 1.25 eV for pure Ni-BaTiO 3 interfaces.

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