High Temperature, High Energy Density Dielectrics for Power Electronics Applications 2012-01-2208

Mn and/or rare earth-doped xCaTiO₃ - (1-x)CaMeO₃ dielectrics, where Me=Hf or Zr and x=0.7, 0.8, and 0.9 were developed to yield materials with room temperature relative permittivities of Ε_r ~ 150-170, thermal coefficients of capacitance (TCC) of ± 15.8% to ± 16.4% from -50 to 150°C, and band gaps of ~ 3.3-3.6 eV as determined by UV-Vis spectroscopy. Un-doped single layer capacitors exhibited room temperature energy densities as large as 9.0 J/cm₃, 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 room temperature values (9.5 J/cm₃) were observed up to 200°C. At 300°C, energy densities as large as 6.5 J/cm₃ were measured. These observations suggest that with further reductions in grain size and dielectric layer thickness, the xCaTiO₃ - (1-x)CaMeO₃ system is a strong candidate for integration into future power electronics applications.

To further improve the high temperature, high field reliability of these material systems, rare earth donor doping has been utilized. Initially, 1 mol% doping with Dy, Gd, and Sm showed the most significant reduction in high temperature, high field conductivity. Further investigation of Dy co-doping with 0.5 mol% Mn , Mg, and (Mn+Mg) showed the most significant increase in Ca(Ti₀.₈Hf₀.₂)O₃ resistivity from 4.61 MΩ.m with only Mn doping to 176 GΩ.cm with Dy and Mg co-doping. Material systems were characterized using capacitance and dielectric loss versus temperature, current-voltage (I-V), UV-Vis spectroscopy for band gap determination, and polarization versus field measurements.