1070-4272/03/7605-0745$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 5, 2003, pp. 745!750. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 5,
2003, pp. 774!778.
Original Russian Text Copyright + 2003 by Sokolov, Valova, Tarlakov, Pronkin.
AND CORROSION PROTECTION OF METALS
Effect of Lithium Sulfide on Electrical Properties
I. A. Sokolov, N. A. Valova, Yu. P. Tarlakov, and A. A. Pronkin
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received June 24, 2002; in final form, March 2003
Abstract-The temperature and concentration dependences of the electrical conductivity was studied in Li
glasses. The effect of lithium sulfide additions (22.5325 mol %) to LiPO
on the electrical conductivity
was studied. The nature of the conductivity was studied over the whole range of Li
S concentrations using
Tubandt’s procedure, and the contribution of electronic component to the total electrical conductivity was
examined by Liang3Wagner’s polarization method.
Ion-conducting substances used as solid elec-
trolytes (SELs) for chemical current sources and in
producing electrochemical transducers and ion-selec-
tive sensors attract intent researchers’ attention. Crys-
talline compounds are most commonly used as SELs;
however, glassy compounds are also given a consider-
able attention. These latter have a number of ad-
vantages over crystalline SELs: they are weakly sensi-
tive to impurities and convenient in processing; they
allow vacuum-tight connections to be ensured. Elec-
trical parameters of glassy compositions are highly
stable and reproducible. Moreover, the electrical con-
ductivity of glassy compositions is one or two orders
of magnitude higher than the conductivity of crystal-
line compounds of the same composition.
In SEL, the electronic component of electrical con-
ductivity is absent, and the total conductivity is deter-
mined by the migration of ions in an electric field.
The expression for the total conductivity of SEL tak-
ing into account the contribution of both positive and
negative current carriers has the form
s = s
where s is the total electrical conductivity; s
electrical conductivities determined by the migration
of positive and negative current carriers, respectively;
n, number of molecules per unit volume; q = ez, elec-
trical charge of a carrier; x
, mole fractions
of cations and anions; and m
, ionic mobilities.
Often one kind of the current carriers dominates
in the electrical conductivity. In this case, the con-
ductivity of glassy systems can be described by the
s = na(ez)m, (2)
where a is the degree of dissociation.
It follows from relationship (2) that an increase in
the conductivity can be achieved by increasing both
the number of current carriers and their mobility.
The electrical conductivity of binary alkali oxide
glasses increases as the content of an alkali metal
oxide increases. Therefore, seemingly, glassy SELs
should be searched for among the systems into which
a maximal amount of current carriers could be intro-
duced. However, this line is limited by the fact that
glasses with a high M
O content (M = Li, Na, K, etc.)
have a low chemical stability and readily crystallize.
At the same time, the number of ions participating
in current transfer can be increased at the expense of
decreasing the energy of their bonding with the glass
matrix. This can be achieved by introducing inorganic
salts with large anions (SO
, and halide ions)
into the glass composition. In this case, the structure
of the starting glass becomes loosened, and the elec-
trical conductivity increases .
As believed in , the substitution of sulfur(II)
ions for oxygen ions in the glass structure should also
be accompanied by an increase in the ionic conductiv-
ity. In fact, sulfur(II) ions are larger than oxygen ions
= 1.84 and r
= 1.40 A) and have a more pro-
nounced tendency to form covalent bonds. Therefore,
the energy of interaction between sulfur-containing
glass fragments and alkali metal ions is lower than in
oxide glasses. Consequently, the energy of dissocia-
tion of polar structural chemical units containing