dThe major objectives of this study were to examine
electrical conduction properties of BaTiO3-based multilayer
ceramic ( MLC ) capacitors in order to gain a better
understanding of the conduction transport mechanisms inside
the devices. The experiments involved mainly leakage current
versus time measurements under both low temperature-low
voltage stress and high temperature-high voltage stress.
It was established that leakage current conduction in a
MLC capacitor under temperature-voltage stress can be
divided into three different conduction regions due to
different mechanisms. Those regions are polarization
current, DC conduction current and degradation current.
The polarization current decreases with time as a power law
relation, i.e. Ic(t) t-m where the exponent value m is
strongly dependent on the type of capacitor and temperature,
but is only weakly dependent on the applied voltage.
It has been proposed that two degradation models ( a
charge carrier concentration model and a reduction of grain
boundary barrier height model ) can explain the degradation
behavior for the Z5U devices tested. Degradation
measurements indicate that the lifetime for Z5U capacitors
can be described by Minford's expression. However, these
models account only partly for X7R degradation. X7R
behavior, is characterized by an early power law time
dependence, followed by exponential voltage dependence.
The most probable conduction transport mechanism in X7R
capacitors is small polaron hopping, while grain boundary
transmission may be the predominant conduction transport
mechanism in Z5U capacitors.
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