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this page : Lithium & Ceramics, by Smart.Conseil
(translated by E. Bastarache)
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LITHIUM
& CERAMICS
by
Smart.Conseil
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- This
alkaline metal is the lightest of known metals (Li,
atomic mass 6.941).
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-
- In
ceramics it is found in the oxidized state, Li2O
(molar mass 29.881
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-
- Classified
as the 33th most abundant element on the planet, this
metal is present in deposits coming from salt lakes,
deposits of silicates (spodumene, petalite,
lepidolite), of phosphates (amblygonite), of
phyllosilicates coming from the modification of
volcanic ash (ex: hectorite in California) and of
borates like jadarite (Serbia).
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- Today
the demand for this metal for the production of
lithium-ion batteries used in data processing and
telephony is enormous. Even if it is used rather
little outside of ceramics its price currently beats
records.
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- Lithium
oxide, Li2O, is the most potent flux among alkaline
oxides, one can classify it as follows: Li2O > Na2O
> K2O. It is a very active flux which strongly
decreases the viscosity of glazes. According to the
proportions used, it lowers also the thermal
dilatation coefficient of glazes and of ceramic bodies
for high temperature.
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- In
current ceramics lithium is useful
:
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- -
In flameware bodies intended to produce cooking pieces
going directly on the flame (see also the article "
Flameware
" by Ron Probst on Smart.Conseil). Li2O reduces the
thermal expansion and improves the properties of
resistance to thermal shock.
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- -
In glazes. Li2O, introduced from chemicals (carbonate
of lithium, lithium fluoride) or natural mineral
compounds (spodumene, petalite,…), is a powerful
flux in particular when associated with potassium and
sodium feldspars.
- Its
melting action begins at 750-780°C. It allows to
strongly lower the viscosity of molten glazes. Used up
to 1 to 2% it can reduce the maturation temperature of
a glaze by 50 to 100°C.
- In
important additions (> 3%) it strongly reduces the
thermal dilatation coefficient and can lead to
shivering (shivering is the opposite of crazing).
Lithium also improves the resistance to scratching.
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- As
a general rule one uses lithium carbonate when one
wants to introduce lithium alone into a glaze. The
melting point of lithium carbonate is 723°C (in
air).
- Lithium
carbonate is not very soluble (13.1 g. per liter of
water at 20°C) contrary to other salts of
alkaline elements. This solubility decreases with the
rise in temperature.
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- Solubility
of lithium carbonate in water
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- The
least soluble raw materials containing lithium are:
lithium carbonate, lithium frits (rather rare
alas…) and minerals such as spodumene, lithium
feldspar, amblygonite and lepidolite.
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- In
high temperature glazes, Li2O attacks silica and
alumina of the shard, which allows the formation of an
effective transition layer to lower the tensions of
dilatation. That also makes it possible to make at
equal temperature glazes with more silica and alumina,
more stable and more resistant.
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- Molar
factors of alkaline oxides for the calculation of the
elasticity of multi-component glasses according to A.A
Appen :
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- Li2O
: 78.45 Gpa (ou
8 x 10-5 kgf/cm²)
- Na2O
: 58.35 GPa (ou
5.95 x 10-5 kgf/cm²)
- K2O
: 40.21 GPa
(ou 4.1 x 10-5 kgf/cm²)
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- Li2O
increases the elasticity modules of glazes
(approximately twice as much as K2O).
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- Chart
of natural and chemical compounds :
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Mineral
Compounds :
|
Chemical
Formula
|
Li2O%
|
Al2O3%
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SiO2%
|
Molar
Mass
|
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Aluminosilicates
:
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-
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-
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-
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-
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Eucryptite
(E)*
|
Li2O.Al2O3.2SiO2
|
11.86
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40.46
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47.68
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252
g
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Spodumene
(S)*
|
Li2O.Al2O3.4SiO2
|
8.03
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27.40
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64.57
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372.16
g
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Lithium
Feldspar (R)*
|
Li2O.Al2O3.6SiO2
|
6.07
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20.71
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73.22
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492.32
g
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Petalite
(P)*
|
Li2O.Al2O3.8SiO2
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4.88
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16.65
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78.47
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612.48
g
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Other
Minerals :
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Chemical
Formula
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Empirical
Formula
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Li%
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Molar
Mass
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Amblygonite
|
(Li,Na)Al(PO4)(F,OH)
|
Li0.75
Na0.25 Al(PO4)
F0.75
(OH)0.25
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3.44
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147.90
g
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Lepidolite
|
K(Li,Al)3(Si,Al)4
O10
(F,OH)2
|
KLi2AlSi4O10F(OH)
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3.58
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388,30
g
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Chemical
Compounds :
|
-Chemical
Formula
|
Li2O%
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CO2%
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Li%
|
Molar
Mass
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Lithium
carbonate
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Li2CO3
|
40.44
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59.56
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18.74
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73.89
g
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Lithium
fluoride
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LiF**
|
-
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-
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26.75
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25.94
g
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- *
: See ternary diagram hereafter
- **
: 1 mole of LiF (25.94 g) will give 0.5 mole of Li2O
in the ceramic product that is to say 14.94 g
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- Ternary
diagram Li2O.Al2O3.SiO2 (L.A.S) :
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- The
ternary diagram Li2O-Al2O3-SiO2 provides important
information concerning the useful phases for the
design of vitroceramics.
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- Vitroceramics
are ceramic materials obtained by a controled process
of nucleation-growth applied to an " Ad hoc " vitreous
matrix. These vitroceramic materials are those which
have been most largely used because of their low
dilatation coefficients, null or negative and also for
their thermal and chemical stability.
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- Examples
:
- -
Lithium enters culinary vitroceramics for cooking
which go on the flame (ex: famous pans of amber
glass…).
- -
Lithium is also used for the optical vitroceramics
intended for telescopes of utmost precision because
they require an extremely low linear dilatation
coefficient.
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 - Phase
diagrams Li2O - Al2O3 - SiO2
- with
indication of the vitreous zones in yellow,
- of
the lithium compounds P = Petalite, R = Lithium
Feldspar, S = Spodumene, E = Eucryptite
- and
of the zones with negative thermal dilatations I and
II in green
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- The
vitreous zone in this ternary system is crossed by
that of minerals with low or negative thermal
dilatation coefficients (points P, R, S, E in the
zones in green). The vitreous compounds located along
the Li2O-Al2O3-SiO2 line present an aptitude to
produce fast crystallizations in - eucryptite and in -
spodumene.
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- Extracts
of summaries of publications by V.G. AVETIKOV in
connection with porcelain bodies containing spodumene
:
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- "
The ternary system Li2O-Al2O3-SiO2 (L.A.S.) contains
many compounds like eucryptite (Li2O-Al2O3-2SiO2),
spodumene (Li2O-Al2O3-4SiO2), lithium feldspar
(Li2O-Al2O3-6SiO2) and petalite (Li2O-Al2O3-8SiO2).
These various mineral compounds of lithium are usable
in ceramic pieces."
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- "
Several of these compounds, and in particular
spodumene, used in the development of ceramic bodies
by addition of argillaceous and mineral matters give
very weak thermal dilatations, and even negative in
the range of temperature going from 0 to 800°C."
-
- =>
This is what one seeks with the special bodies that go
on the flame.
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- "
For example, when one replaces pegmatite or feldspar
of a porcelain body by spodumene, the coefficient of
dilatation may be lowered by 2 to 3 times compared to
its value in a feldspathic product."
-
- "
In porcelain bodies in which Li2O was added up to a
total value of 2%, the mechanical properties and the
electrical resistance of the shapes containing
spodumene approach those of the porcelains for high
voltage (high voltage insulators). The thermal
dilatation coefficient is lower (1.5 to 2.5 x10-6
°C-1) in the range of 0 to
200°C."
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- "
A special attention is to be paid to the conditions of
cooling of the products after firing. The pieces
containing approximately 2% Li2O which cool too slowly
have altered structures and are not very dense, their
dilatation is negative. V.G. AVETIKOV concludes that
this is due to recrystallizations of lithium
aluminosilicates caused by a too slow cooling."
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- "
To obtain dense porcelain structures, the speed of
cooling between 1300°C and 1100°C must be
approximately 300°C per hour. Under these
conditions the thermal dilatation coefficient remains
positive. The speed of cooling under 1100°C does
not affect the quality of the shard."
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- "
The tendency to recrystallize is directly related to
the content in Li2O."
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- "
The resistance to thermal shock of the dense shards
(not very porous) increases with the amount of Li2O."
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- Lithium
favors nucleation and growth in crystalline glazes :
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- Lithium
is generally introduced in small quantities from 1 to
2% of Li2O in this type of glaze.
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- Upon
cooling, lithium favors the formation of crystalline
aluminosilicates and in particular the formation of
spodumene from the ingredients of the vitreous flow.
These nucleations allow to sow the glaze more quickly
and improve its crystallizing capacity.
- These
glazes require a very good control of the cycle of
firing cooking in order to pass to the phase of growth
with precision. The reproducibility of this type of
glaze can be rather difficult.
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- The
crystalline growth is influenced by the active role of
lithium which lowers the viscosity and the surface
tension of crystalline glazes (*).
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- A
more fluid glaze favors a faster growth of the
crystals. It allows a more important mobility of the
crystallizing elements and colourants and favors their
migration.
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- The
reduction of surface tension of the glaze favors
crystals with low density structures because these
develop themselves and move more freely on the surface
of the glaze. They are to some extent " more
relaxed"…
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- In
short, with lithium low viscosity more quickly
nourishes the crystals and a lower surface tension
favors their not very dense spreading out on the
surface of the glaze. With a time of growth adapted, a
crystalline glaze with lithium (a few % of Li2O) will
rather easily give very large crystals with diaphanous
textures. ("transparency" and "wings of dragonfly"
effects ).
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- It
is the same for the other types of glazes whose
viscosity and surface tension are close to those with
lithium.
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- But
attention to glaze runs…
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-
 - example
of semi-translucent zinc silicate crystals on a glaze
with lithium (2.5% Li2CO3)
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- (*)
: Caution!! Here it is question of crystalline glazes,
therefore of glazes with heterogeneous phases
(vitreous and crystalline). Calculations of physical
properties applied to pure glasses, such as those of
the thermal dilatation coefficient, superficial
tension, elasticity, cannot be applied to these
compositions.
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- Toxicity
of lithium :
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- See
Edouard Bastarache's article on lithium
(Québec) : Lithium.htm
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- Examples
of lithium containing glazes :
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CONE
04 Lithium Containing Glazes
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(1060-1080°C) - From : Edouard
Bastarache (http://www.blogger.com/profile/10622613356744391469)
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- 01
- Sorel Jade Green Glaze
Recipe
by Edouard
Bastarache http://04glazes.blogspot.com/
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- Firing:
Orton cone 04
- North
American raw materials were
substituted for by European
ones.
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Washed
hardwood ash (Oak)
|
36
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Mixed
Feldspar ICE10
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14.5
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Ferro
Frit 3134 (available in
Europe)
|
23
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Kaolin
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14.5
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Lithium
carbonate
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12
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Bentonite
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2
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Zircon
(Zirconium silicate)
|
15.5
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Black
copper oxide
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3.5
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Shiny
glaze with areas of surface
microcrystals (spodumene
crystallizations at the time of
cooling).
|
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- 02
- Ginette's Blue Glaze (My
wife)
Recipe
by Edouard
Bastarache http://04glazes.blogspot.com/
|
|
- Firing
: Orton cone 04
- North
american raw materials were
substitued for european
ones.
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Washed
hardwood ash (oak)
|
35
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Mixed
feldspar ICE10
|
14
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Ferro
frit 3134 (available in
Europe)
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25
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Kaolin
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14
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Lithium
carbonate
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12
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Bentonite
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2
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Zircon
(Zirconium silicate)
|
15
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Black
cobalt oxide
|
5
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- Shiny
glaze with areas of surface
microcrystals (spodumene
crystallizations at the time
of cooling).
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- Richard
Zakin says that we should not
put more than 5% Lithium
Carbonate in a glaze (in his
software Describ9) because
once applied, the dry glaze
can crack and flake
off.
-
- We
checked that and it is true,
then the trick is to rub the
glaze while the shard is still
wet considering the recent
application of the glaze; and
it works.
- As
for Spodumene, it is the same
thing (to flake off). He also
says not to put more than 35%
Spodumene.
|
-
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- LITHIUM
CRYSTALLINE
Glaze
for Cone 6
(1220-1240°C) - From John Sankey's
database
(http://www.johnsankey.ca/glazedata.html)
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- 03
- Turquoise Crystalline Glaze
Recipe
by Alisa
Clausen http://www.alisapots.dk/miscellaneous.htm#
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- Firing
: cône cone 6
- Cooling
: fast down to 1100°C then
lowering to 800°C at
80°C per hour
|
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Potassium
feldspar
|
36
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Zinc
oxide
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24
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Silica
|
15
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Calcium
carbonate
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13
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Lithium
carbonate
|
7
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Kaolin
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5
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Rutile
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5
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Copper
carbonate
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1
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Shiny
very fluid glaze with large green
and blue crystals.Looks like an
aerial view of the Caribbean
islands. The crystals have clear
structures like gems.
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- 04
- Orange - Blue Crystalline
Glaze
Recipe
by Alisa
Clause http://www.alisapots.dk/miscellaneous.htm#
|
|
- Firing
: Orton cone 6
- Cooling
: fast down to 1100°C then
down to 800°C at 80°C
per hour.
|
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Potassium
feldspar
|
36
|
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Zinc
oxide
|
24
|
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Silica
|
15
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Calcium
carbonate
|
13
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Lithium
carbonate
|
7
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Kaolin
|
5
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Black
nickel oxide
|
1
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Orange
to rusty glqze background with large
luminous blue crystals and dark blue
centers. The crystals have clear
structures like gems.
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- GLAZES
containing
lithium for cone
9.5
(1280-1300°C)
- From : Edouard Bastarache
(http://www.blogger.com/profile/10622613356744391469)
-
- 05
- White-Rusty Shino
glaze
Recipe
by Edouard
Bastarache
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- Firing
: Orton cone 9.5 in
reduction
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Nepheline
syenite
|
86
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Kaolin
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3
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Silica
|
4
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Alumina
hydrate
|
3
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Lithium
carbonate
|
4
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Bentonite
|
3
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White
and rusty glaze due to the clay
containing iron.
Lithium
carbonate is added to thwart the
surface flaws generated by the
excess of Nephelite/Syenite (Na2O).
|
- 06
- Brick Red Shino
Recipe
by Edouard
Bastarache
|
|
|
Firing
: Orton cone 9.5 in
reduction
The
North American raw materials were
substituted for by European
ones.
|
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Nepheline
syenite
|
42
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Mixed
Feldspar ICE10
|
44
|
|
Kaolin
|
11
|
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Lithium
carbonate
|
3
|
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Bentonite
|
4
|
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Red
iron Oxide
|
2
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- Textured
brick red glaze
|
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- Smart.Conseil
©
September
2011
-
FRANCE
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écrit et documenté par le
propriétaire du site // Contact :
Smart2000@wanadoo.fr
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