Development of large-area BaTi03 ceramics with optimized depletion regions as dielectrics for planar power electronics

High-voltage (500 V) barium titanate (BaTiO₃) ceramics are under development as compact high-permittivity dielectrics for planar structures in integrated power-electronic converters. Dielectric requirements include a high permittivity for meeting the dimensional constraints in converters, a high power-handling capability, low loss, and flat permittivity and tanδ frequency responses up to 1 MHz. Dopant materials examined here focused on fine powders of Al₂0₃ and Al added during the sintering process. Best results were obtained by diffusion of externally-placed Al during the sintering cycle, with BaTiO₃ permittivities ε_r ~1000, and loss tangents tanδ <~4% over 1 kHz to 1 MHz. This paper describes fabrication and doping methods aimed at achieving such specifications. Electrical C-V testing up to 500 V on specimens of thickness 0.5-0.7 mm (with E-field intensities up to 10⁶ V/m) was carried out using l-kHz bridge measurements, as well as in a power-electronic chopper circuit employing a BJT switch, and operating up to 500 V with pulse widths ~25 μs and repetition rates ~4 kHz