Submicrosecond Pulsed Power Capacitors Based on Novel Ceramic Technologies

Abstract

Capacitor energy density for submicrosecond discharge applications was investigated for capacitors based on the following: 1) polymer–ceramic nanocomposite (PCNC); 2) antiferroelectric (AFE); and 3) paraelectric (PE) ceramic dielectrics. The developmental PCNC dielectric enabled design, fabrication, and testing iterations to be completed relatively rapidly. The PCNC capacitors were nominally 4 nF and were tested to dc potentials of at least 75 kV. The capacitors were then charged from 20 to 48 kV with a dc high-voltage power supply and discharged into a nearly critically damped test circuit of up to 5 pulses/s (pps) repetition rate for lifetime testing. The discharge time was 65 ns. Shot life as a function of the charge voltage was compared for three design iterations. Changes in the manufacturing of the PCNC capacitors have yielded up to 100x improvements in pulse discharge life. The 1–2-kV prototype, nonlinear (antiferroelectric and paraelectric) multilayer ceramic capacitors had zero-voltage capacitance ratings of between 60 and 300 nF. They were charged to their operating voltage and discharged into a nearly critically damped load in 2–6 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{s}$</tex> </formula> , depending on their capacitance, at repetition rates of up to 75 pps. Their operating voltage for fast, repetitive discharge was determined for lifetimes consistently over <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$10^{5}$</tex> </formula> shots. Discharge energy densities of 0.27–1.80 J/cc and energy losses of 7.9–36.8% were obtained for the packaged multilayer capacitors with different formulations of nonlinear dielectrics. Increased field-induced strain was correlated with increased permittivity and contributed to the limitations on the operating voltage. Multilayer ceramic capacitors fabricated from AFE and PE ceramic dielectrics have the potential to achieve high energy density owing to their high relative permittivities that vary with applied electric field, assuming they can be scaled up to sufficiently high voltages.