Glossary
317
Potentiometric sensor – Electrochemical device for measuring the activity of a
chemical species by measuring the potential difference across an open circuit. The corresponding elementary cell involves one or more electrolytes
inserted between two electrodes, which often serve as current collectors.
Potentiostatic mode – A technique for plotting the characteristic potential/current
of an electrode. In potentiostatic mode, the potential difference between the
working electrode and the reference electrode is fixed and the current through
the working electrode is recorded.
Power density – For an electrochemical generator, the power density is the maximum power that the system can supply at the active surface of the electrodes.
It is given in W cm
–2
.
Relaxation frequency – A characteristic frequency observed during polarization of
dipoles by an alternating electric field when the dielectric loss factor is maximal. For a given phenomenon, it depends only on temperature. The inverse
of the relaxation frequency is the relaxation time. The relaxation frequency
and relaxation time are strongly correlated with the electrical conductivity.
Schottky disorder (pair) – A pair consisting of a cationic vacancy and an anionic
vacancy formed by thermal agitation in a pure ionic crystal. An example is
the pair V ′
Na + V
•
Cl sodium chloride NaCl.
Sitoneutrality – Expresses the conservation of the ratio of the number of anionic
(cationic) sites to the number of cationic (anionic) sites in an ionic crystal. In
a crystal with the formula M a X b , the sitoneutrality expression is
Number of sites X
Number of sites M
b
a
=
Solid solution – In thermodynamics, a solid solution is a mixture of pure components forming a homogeneous solid. These components are often of a mineral
phase (metals, ionic crystals). The properties of a solid solution can differ
greatly from those of the constituent bodies. For example, this is the case of
doped silicon-based semiconductors in microelectronics.
Stabilized zirconia – A solid solution of oxides involving zirconium dioxide ZrO 2
and an oxide dopant such as MO or M 2 O 3 . The presence of the oxide dopant
stabilizes the fluorine-type cubic structure over a large range of temperature,
composition, and oxygen partial pressure. The most often used material
is yttria-stabilized zirconia with the formula (ZrO 2 ) 0.92 -(Y 2 O 3 ) 0.08 , for its
ionic-conduction properties.
Steam reforming – Steam reforming is a catalytic chemical reaction that, with the
help of steam, converts hydrocarbons to dihydrogen and carbon monoxide.
317
Potentiometric sensor – Electrochemical device for measuring the activity of a
chemical species by measuring the potential difference across an open circuit. The corresponding elementary cell involves one or more electrolytes
inserted between two electrodes, which often serve as current collectors.
Potentiostatic mode – A technique for plotting the characteristic potential/current
of an electrode. In potentiostatic mode, the potential difference between the
working electrode and the reference electrode is fixed and the current through
the working electrode is recorded.
Power density – For an electrochemical generator, the power density is the maximum power that the system can supply at the active surface of the electrodes.
It is given in W cm
–2
.
Relaxation frequency – A characteristic frequency observed during polarization of
dipoles by an alternating electric field when the dielectric loss factor is maximal. For a given phenomenon, it depends only on temperature. The inverse
of the relaxation frequency is the relaxation time. The relaxation frequency
and relaxation time are strongly correlated with the electrical conductivity.
Schottky disorder (pair) – A pair consisting of a cationic vacancy and an anionic
vacancy formed by thermal agitation in a pure ionic crystal. An example is
the pair V ′
Na + V
•
Cl sodium chloride NaCl.
Sitoneutrality – Expresses the conservation of the ratio of the number of anionic
(cationic) sites to the number of cationic (anionic) sites in an ionic crystal. In
a crystal with the formula M a X b , the sitoneutrality expression is
Number of sites X
Number of sites M
b
a
=
Solid solution – In thermodynamics, a solid solution is a mixture of pure components forming a homogeneous solid. These components are often of a mineral
phase (metals, ionic crystals). The properties of a solid solution can differ
greatly from those of the constituent bodies. For example, this is the case of
doped silicon-based semiconductors in microelectronics.
Stabilized zirconia – A solid solution of oxides involving zirconium dioxide ZrO 2
and an oxide dopant such as MO or M 2 O 3 . The presence of the oxide dopant
stabilizes the fluorine-type cubic structure over a large range of temperature,
composition, and oxygen partial pressure. The most often used material
is yttria-stabilized zirconia with the formula (ZrO 2 ) 0.92 -(Y 2 O 3 ) 0.08 , for its
ionic-conduction properties.
Steam reforming – Steam reforming is a catalytic chemical reaction that, with the
help of steam, converts hydrocarbons to dihydrogen and carbon monoxide.