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In reality, the electrode hosts two opposing reactions of unequal rates. To each
reaction is associated an exchange-current density whose absolute value i 0 is
the density of the equilibrium exchange current.
Equivalent electrical circuit – The equivalent electrical circuit is a mathematical
model obtained by combining pure dipolar electrical elements (R, C, L) and
is used to determine the properties of a sample by mathematically adjusting
its parameters at experimental test points. This adjustment can be done, for
example, by a least-squares fit.
Extrinsic defect – A structure defect due to the presence of impurities or dopants
in an ionic crystal. Its definition requires a notation for the introduction of
the impurity or dopant in the pure crystal.
Formula unit – The simplest and most succinct formula to denote a chemical compound. For example, the formula unit associated with titanium dioxide is TiO 2
instead of Ti 2 O 4 or Ti 16 O 32 , which are also valid in terms of stoichiometry.
Free volume model – The free volume model is a microscopic model developed
to explain the mechanical or electrical behavior of amorphous electrolytes
or polymers. From an electric viewpoint, the mobility of charge carriers is
said to be “activated” below the ideal glass transition temperature T G and
“assisted” by entropic redistribution above that temperature. The theoretical
models used to explain this behavior are the activated hopping model below
T G and the Vogel-Tammann-Fulcher (VTF) model above T G .
Fuel cell – A system for converting chemical energy into electrical energy that
involves the following chains: oxidant, electrode / electrolyte / electrode, reducer. Oxidants such as oxygen or chlorine constitute oxidizing agents, and
reducers such as hydrogen, methane, or methanol constitute fuels.
Geometric factor – For a sample of simple geometry (e.g., cylinder, parallelepiped, …),
it is the ratio between sample thickness and the area over which is deposited
the electrodes. It connects the electrical resistance, which is measurable, to
the conductivity of a phase.
GIR – Abbreviation meaning “gradual internal reforming.”
Glass transition temperature – The glass transition temperature T G corresponds to
the change from a liquid state (supercooled) to a solid state (metastable) and
occurs when the viscosity of the liquid attains the conventionally agreed upon
value of 10
12
Pa s. The temperature at which this transition occurs cannot be
precisely defined because it depends on the speed with which the liquid is
cooled (or quenched). We thus speak of the glass transition interval.
Impedance – The response of an electric circuit or of a material to an alternating electric current. The impedance of a circuit or a material is defined as a
Solid-State Electrochemistry
In reality, the electrode hosts two opposing reactions of unequal rates. To each
reaction is associated an exchange-current density whose absolute value i 0 is
the density of the equilibrium exchange current.
Equivalent electrical circuit – The equivalent electrical circuit is a mathematical
model obtained by combining pure dipolar electrical elements (R, C, L) and
is used to determine the properties of a sample by mathematically adjusting
its parameters at experimental test points. This adjustment can be done, for
example, by a least-squares fit.
Extrinsic defect – A structure defect due to the presence of impurities or dopants
in an ionic crystal. Its definition requires a notation for the introduction of
the impurity or dopant in the pure crystal.
Formula unit – The simplest and most succinct formula to denote a chemical compound. For example, the formula unit associated with titanium dioxide is TiO 2
instead of Ti 2 O 4 or Ti 16 O 32 , which are also valid in terms of stoichiometry.
Free volume model – The free volume model is a microscopic model developed
to explain the mechanical or electrical behavior of amorphous electrolytes
or polymers. From an electric viewpoint, the mobility of charge carriers is
said to be “activated” below the ideal glass transition temperature T G and
“assisted” by entropic redistribution above that temperature. The theoretical
models used to explain this behavior are the activated hopping model below
T G and the Vogel-Tammann-Fulcher (VTF) model above T G .
Fuel cell – A system for converting chemical energy into electrical energy that
involves the following chains: oxidant, electrode / electrolyte / electrode, reducer. Oxidants such as oxygen or chlorine constitute oxidizing agents, and
reducers such as hydrogen, methane, or methanol constitute fuels.
Geometric factor – For a sample of simple geometry (e.g., cylinder, parallelepiped, …),
it is the ratio between sample thickness and the area over which is deposited
the electrodes. It connects the electrical resistance, which is measurable, to
the conductivity of a phase.
GIR – Abbreviation meaning “gradual internal reforming.”
Glass transition temperature – The glass transition temperature T G corresponds to
the change from a liquid state (supercooled) to a solid state (metastable) and
occurs when the viscosity of the liquid attains the conventionally agreed upon
value of 10
12
Pa s. The temperature at which this transition occurs cannot be
precisely defined because it depends on the speed with which the liquid is
cooled (or quenched). We thus speak of the glass transition interval.
Impedance – The response of an electric circuit or of a material to an alternating electric current. The impedance of a circuit or a material is defined as a
Solid-State Electrochemistry