First-order reversal curve (FORC) distributions as well as the ac field dependence of the dielectric permittivity were investigated for model BaTiO 3 -based multilayer ceramic capacitors in which the dielectric grain size was varied from 0.28 to 0.39 lm. It was found that as the grain size decreased, the high-field dielectric permittivity, the peak in the irreversible FORC distribution at origin, and the reversible FORC distribution at zero bias decreased. The reversible FORC distribution of all the parts converged at high biases, indicating that the grain size dependence was influenced by domain wall contributions. Dielectric contributions from the core and shell were estimated based on the temperature dependence of the permittivity. Not unexpectedly, the relative response of the core decreased while that of the shell increased as the grain size decreased. A Preisach model using the measured FORC distribution gave a good fit to the experimental polarization-electric field loops.

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This paper investigates the susceptibility of multilayer ceramic (MLC) capacitors to high-voltage electrical fast transients (EFTs). X7R and NP0 MLC capacitors with a 50 V voltage rating and 0603 package size were tested. X7R capacitors often failed during a spike in the voltage, but exhibited no obvious degradation in the measured insulation resistance at low voltages immediately after the failure. NP0 capacitors usually failed by suddenly shorting and maintaining the short after the failure. With the application of additional voltage spikes, some X7R capacitors exhibited a full recovery in terms of the measured resistance, returning to their initial state. The resistance of an X7R capacitor damaged by an EFT event is a function of the applied voltage. The terminal impedance can be modeled as two diodes in parallel.

Multilayer ceramic capacitors remain an important component in high temperature circuitry due to the general robustness of ceramics at application temperatures greater than 200°C. However, standard MLCC dielectric compositions either exhibit very low dielectric constants at high temperatures or show excessive capacitance loss with increasing temperature in this regime. Many also see a significant degradation in insulation resistance, leading to very low RC products for the materials. Stability of properties with dielectric field is also a critical factor in many applications, both for improved energy storage and capacitance per unit volume. In recent years, a new class of weakly-coupled relaxor ceramic compositions has emerged which offer significant benefits in dielectric constant and capacitance stability at high temperatures. Tailoring of these compositions can offer increased capacitance stability over wide temperature regimes, or maximized capacitance in the high temperature (>200°C) realm. In this discussion, a comparison is made between MLCCs constructed of a standard commercial dielectric material and one of these new compositions. Emphasis on performance at high temperature and the outlook for expansion of this class is given.

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