2 Binary Systems: O – Pb
1
O – Pb (Oxygen – Lead)
Fig. 1. Calculated phase diagram for the system O-Pb.
The O-Pb system is of primary technical importance because of the wide use of lead-bronze, lead-tin solders, and lead-acid accumulators. Lead oxides are also components of piezoelectric and high-temperature
superconducting ceramics. The O-Pb system was reviewed by [88Wri], who gave an exhaustive summary
of the numerous studies and discussed the controversies and uncertainties.
A consistent thermodynamic description of the O-Pb system through the entire composition range has been
published by [98Ris]. The gas phase was treated as an ideal mixture containing the species Pb, Pb2 , PbO,
Pb2 O2 , Pb3 O3 , Pb4 O4 , Pb5 O5 , Pb6 O6 , O, O2 , and O3 . The liquid phase was described by a two-sublattice
partially ionic liquid model which allows compositional variations between Pb and PbO. The solid phases
PbO-l, PbO-m, Pb3 O4 , Pb12 O17 , Pb12 O19 , and PbO2 were approximated as stoichiometric compounds and
the fcc phase was considered as pure lead. The thermodynamic description is in close agreement with the
most reliable data on the stability limits of the higher oxides in the PbO-PbO2 part. For the Pb-PbO range,
the spread in the data concerning the miscibility gap in the liquid phase is large and results of the leastsquares optimisation depend on the selected dataset. All experimental studies are confined to temperatures
below 1473 K. The choice made in [98Ris] results in the calculated phase diagram at 1 bar pressure, where
the miscibility gap is predicted to close just above 1800 K.
Recently, the description of the liquid phase in O-Pb has been modified in conjunction with the thermodynamic optimisation of the ternary Cu-O-Pb system [03Zin]. The experimental data of the ternary system
indicate a lower solubility limit of oxygen in the Pb-rich liquid than calculated with the description of
[98Ris] and thus, another dataset has been preferred. The critical point of the miscibility gap is then shifted
to about 4700 K. The new set of thermodynamic parameters obtained in [03Zin] is recommended, since it
is based on reasonable data selection by applying additional constraints from a ternary system.
Landolt-Börnstein
New Series IV/19B
SGTE
2
2 Binary Systems: O – Pb
Table I. Phases, structures and models.
Phase
liquid
PbO2
Pb12 O19
Pb12 O17
Pb3 O4
PbO-m
PbO-l
fcc
Strukturbericht
C4
···
···
···
···
B10
A1
Prototype
TiO2 (rutile)
···
···
Pb3 O4 -t
PbO-m
PbO-l
Cu
Pearson
symbol
tP 6
mP 62
oP 58?
tP 28
oP 8
tP 4
cF 4
Space
group
SGTE
name
Model
P 42 /mnm
P c or P 21 /c
P mc21 ?
P 42 /mbc
P bma
P 4/nmm
F m3m
IONIC LIQUID
PBO2
PB12O19
PB12O17
PB3O4
PBO M
PBO L
FCC A1
2−
Pb2+
,2)q
p (O
Pb1 O2
4+ 2−
Pb2+
5 Pb7 O19
2+
2−
Pb7 Pb4+
5 O17
Pb3 O4
Pb1 O1
Pb1 O1
Pb1
Table II. Invariant reactions.
Reaction
Type
T /K
gas liquid
gas liquid + liquid
gas + liquid PbO-m
PbO-m
+ liquid
liquid gas + PbO-m Pb
3 O4
PbO-m PbO-l
gas + Pb3 O4 Pb12 O17
gas + Pb12 O17 Pb12 O19
liquid PbO-l
+ fcc
gas + Pb12 O19 PbO2
Pb12 O19 PbO2 + Pb12 O17
congruent
gas-eutectic
gas-peritectic
monotectic
gas-peritectoid
polymorphic
gas-peritectoid
gas-peritectoid
degenerate
gas-peritectoid
eutectoid
1923.6
1876.7
1158.6
1156.0
868.7
761.8
634.2
608.5
600.6
524.1
326.9
Compositions / xPb
0.504
0.608
0.001
0.501
0.000
0.500
0.000
0.000
1.000
0.000
0.387
0.504
0.512
0.500
0.500
0.500
0.500
0.429
0.414
0.500
0.387
0.333
0.952
0.500
0.993
0.429
0.414
0.387
1.000
0.333
0.414
∆r H / (J/mol)
−85481
−97273
−13399
−13560
−10580
−513
−3083
−2864
−4774
−7570
−470
Fig. 2. Calculated temperatureactivity phase diagram. Reference
state: 12 O2 (gas, 0.1 MPa).
SGTE
Landolt-Börnstein
New Series IV/19B
2 Binary Systems: O – Pb
3
Table III. Standard reaction quantities at 298.15 K for the compounds per mole of atoms.
xPb
Compound
0.333
0.387
0.414
0.429
0.500
0.500
PbO2
Pb12 O19
Pb12 O17
Pb3 O4
PbO-l
PbO-m
∆f G◦ / (J/mol)
∆f H ◦ / (J/mol)
∆f S ◦ / (J/(mol·K))
∆f CP◦ / (J/(mol·K))
−74226
−82425
−86559
−87964
−94469
−94019
−93906
−100332
−104226
−104775
−109524
−108718
−66.009
−60.060
−59.257
−56.384
−50.495
−49.301
1.988
2.600
2.904
3.072
2.193
2.184
References
[88Wri]
[98Ris]
[03Zin]
H.A. Wriedt: Bull. Alloy Phase Diagrams 9 (1988) 106–127.
D. Risold, J.-I. Nagata, R.O. Suzuki: J. Phase Equilibria 19 (1998) 213–233.
M. Zinkevich, M. Cancarevic, F. Aldinger: unpublished optimization, 2003.
Landolt-Börnstein
New Series IV/19B
SGTE