DEVELOPMENT OF LARGE-AREA BATIO3 CERAMICS WITH OPTIMIZED DEPLETION REGIONS AS DIELECTRICS FOR PLANAR POWER ELECTRONICS

High-voltage (500 V) barium titanate (BaTiO3) ceramics are under devel opment as compact high-permittivity dielectrics for planar structures in integrated power-electronic converters. Dielectric requirements inc lude a high permittivity for meeting the dimensional constraints in co nverters, a high power-handling capability, low loss, and flat permitt ivity and tan delta frequency responses up to 1 MHz. Dopant materials examined here focused on fine powders of Al2O3 and Al added during the sintering process. Best results were obtained by diffusion of externa lly-placed Al during the sintering cycle, with BaTiO3 permittivities e psilon(r) similar to 1000, and loss tangents tan delta similar to 4% o ver 1 kHz to 1 MHz. This paper describes fabrication and doping method s 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 10(6) V/m) was carried out using 1-kHz bridge measurements, as w ell as in a power-electronic chopper circuit employing a BJT switch, a nd operating up to 500 V with pulse widths similar to 25 mu s and repe tition rates similar to 4 kHz.