Improving the frequency response of ceramic dielectrics for high power applications in power electronic converters

High-voltage (1000 V) distributed and lumped ceramic capacitors are under development for diverse applications in integrated power-electronics structures and systems for cost-efficient production. These applications range from systems involving new integrated packaging and manufacturing technologies such as for dc-dc converters, to optimal power-component designs such as in dissipative RCD turn-off snubber circuits for high-power transistor or thyristor switch protection. Their design requires an understanding of the interacting ferroelectric, grain-boundary, and space-charge mechanisms controlling the high-voltage and low-frequency response. This paper relates to an experimental and theoretical study of high-voltage (0 to 1000 VDC) acceptor-doped barium-titanate BaTiO₃ ceramic capacitors, for several possible uses in integrated power-electronic converters with flat voltage and frequency response up to 1 MHz. The paper includes interpretations, based on experiment, of the inter-dependence of (a) ferroelectric-grain, (b) semiconductor-compensation-insulator-compensation-semiconductor (n-c-i-c-n) grain-boundary, and (c) Debye space-charge contributions to capacitance, as functions of acceptor doping