J. Mod. Phys., 2010, 1, 201-205
doi:10.4236/jmp.2010.14030 Published Online October 2010 (http://www.SciRP.org/journal/jmp)
Physical Properties of Lithium Containing Cadmium
Phosphate Glasses
Muhammad Altaf 1, M. Ashraf Chaudhry2
1Department of Physics, Govt. College of Sc ience, Multan, Pakistan
2Department of Physics, Bahauddin Zakariya University, Multan, Pakistan
Received May 1, 2010; revised August 15, 2010; accepted May 14, 2010
Abstract
Lithium cadmium phosphate glasses were prepared by melt quench technique. These glasses contain a mole
% composition of x% Li2O-(50-x)% CdO-50%P2O5. The quantity x varies from 0-40 mole%. The physical
properties reported in this paper are mass density ρ, modulus of rigidity η, coefficient of linear expansion α,
transition temperature Tg, Softening temperature Ts, Oxygen packing density, Molar volume and lithium ion
concentration. The mass density, oxygen packing density, modulus rigidity, transition temperature and sof-
tening temperature show decreasing trend with increasing concentration of lithium ions in these glasses,
where molar volume and coefficient of linear expansion increases with increasing concentration of Li2O.
Keywords: Phosphate Glasse, Mass Density, Modulus of Rigidity, Coefficient of Linear Expansion, Transition
Temperature, Molar Volume
1. Introduction
The competition of speed, cost and reliability of elec-
tronic devices in various applications has led to the re-
search for new materials which can met the specific re-
quirement. The phosphate glasses are among those mate-
rials which have a number of technical and biological
applications [1-3]. Phosphate glasses have a variety of
technological application due to several unique proper-
ties [4]. To investigate the nature of these glasses for
their appropriate applications, study of optical, electrical
and physical properties are necessary. Most of the re-
searchers studied optical and electrical properties to
characterize the phosphate glasses [5-8], whereas the
knowledge of physical properties is equally very helpful
to study the nature of materials.
A general observation of the thermal expansion curve
tells whether the materials under investigation are amor-
phous are crystalline in nature. Experimental results on
physical properties in glassy material have been reported
in literature [9-11].
In the present work physical properties such as mass
density, oxygen packing density, molar volume, modulus
of rigidity, transition temperature, softening temperature
and coefficient of linear expansion were studied to ex-
amine the effect of alkali metal oxide i.e. Li2O on the
cadmium phosphate glasses. According to our survey, no
data has been reported on the physical properties of cad-
mium phosphate glass system containing lithium oxide.
2. Experimental
Chemicals Li2CO3, CdO and P2O5 of purity (99.99%) were
used to prepare Lithium-cadmium-phosphate glasses. The
glass samples were prepared by using 15 g ingredients
mixture of composition x%Li2O-(50-x) %CdO-50%P2O5
in a platinum crucible. The details of preparation of sam-
ples and method of density measurements and modulus
of rigidity have already been described else where
[12,13]. Oxygen packing density, molar volume and
lithium ion concentration were estimated by using fol-
lowing equations respectively,
Oxygen packing density = {1000 × ρ× (O)}/M (1)
Molar volume = M/ρ (2)
Ion concentration = {ρ Navo P}/M (3)
where ρ = mass density
M = Molecular weight of glass composition
O = number of oxygen atoms in the composition
Navo = Avogadro number
and P = nx
where ‘x’ is the mole fraction in glass composition and

M. ALTAF ET AL.
202
‘n’ is the number of atoms of element ions in a given
oxide, i.e. n = 1 for oxides like CdO, ZnO etc and n = 2
for oxides like Li2O, Na2O, etc.
Thermal expansion and coefficient of linear expansion
of fibers of lithium phosphate glasses have been studied
up to 600˚C. These parameters were measured by using a
horizontal tube heating system as shown in Figure 1.
The heating system consists of two equal bore Pyrex
tubes each of 10 cm length. The tubes are fitted together
in a single heating unit so that both the tubes can have
the same temperature. A Cromel-Alumel thermocouple
connected to a Fenwal controller is fitted in one tube and
the glass fiber ‘F’ of length Lo = 10.5 cm is placed in the
other tube. The temperature of the system is controlled
by a temperature controller while the heating rate is con-
trolled through a voltage regulator. Each temperature
was maintained for five minutes to achieve the equilib-
rium.
The increase in the length of the fiber for every 50˚C
rise in temperature (with constant rate of heating) was
measured with a traveling microscope whose least count
is 10 μm. The linear expansion was plotted against tem-
perature as shown in Figure 2. This curve was used to
estimate transition temperature Tg and softening tem-
perature Ts. The coefficient of linear expansion ‘α’ is
then calculated using equation
α= (L)/(Lo t) (˚C)-1 (4)
3. Results and Discussion
The measured results and estimated values of mass den-
sity are listed in Table 1. These results indicate a de-
creasing trend in the density of. x% Li2O-(50-x)%
CdO-50%P2O5 glass system with increasing concentra-
tion of Li2O. Theoretical values of the density were es-
timated by using the relation ρ = ∑ρi xi, where ρi and xi
are the density and fraction of the free oxides respec-
tively. The estimated and the measured values of density
of these glasses are depicted in Figure 3 as a function of
Li2O concentration. It can be seen that estimated values
are higher than measured values. This difference in val-
ues of density may be due to the variation in atomic ar-
rangement between the structure of glass and molecules
of the free oxides. The decrease in the measured density
with the increasing concentration of Li2O agrees qualita-
tively with that predicted by the composition relation,
and it may be due to the replacement of high density
CdO (8.15 g/cm3) as compared with Li2O (2.02 g/cm3).
The estimated oxygen packing density and molar volume
and lithium ion concentration are listed in Table 1 and
are shown in Figures 4, 5, and 6 respectively. These re-
sults show that oxygen packing density decreases where
as molar volume and lithium ion concentration increase
Figure 1. Tube furnace along with temperature controller
for heating the fiber to measure its linear expansion with
the variation temperature.
Figure 2. A plot of linear expansion l versus temperature oC.
Figure 3. Var iation of mass dens ity relative to lithium oxide
concentration (mole%).

M. ALTAF ET AL.
203
Table 1. Variation of mass density, oxy gen packing density, molar volume and lithium ion concentration with respect to glass
composition in mole%.
Density ρ (g/cm3)
Composition Mole %
Li2O-CdO-P2O5 Calculated Measured
Oxygen Paking Density
(g-atom/liter)
Molar Volume Vm
(cm3 )
Li2O ion Concentration
(ion/cm3) × 1021
0%-50%-50% 5.27 3.95 87.57 34.26 00.0
05%-45%-50% 4.96 3.83 86.05 34.87 1.73
10%-40%-50% 4.66 3.69 85.40 35.13 3.43
15%-35%-50% 4.35 3.57 84.33 35.58 5.08
20%-30%-50% 4.04 3.48 83.92 35.75 6.74
25%-25%-50% 3.74 3.34 82.50 36.36 8.28
30%-20%-50% 3.43 3.17 80.06 37.47 9.64
40%-10%-50% 2.82 2.89 76.42 39.26 12.27
Figure 4. A plot of oxygen packing density as a function of
lithium oxide content.
Figure 5. Variation of molar volume with lithium oxide
concentration.
Figure 6. A graph be tween ion c oncentration of lithium and
Lithium oxide content.
with increasing concentration of the lithium oxide. The
replacement of an intermediate/modifier CdO with Li2O
which is a modifier only, develops more non-bridging
oxygen than bridging oxygen in the glass network [15,16].
The development of non-bridging oxygen may flayer-up
the glass system and thus increases its molar volume.
The increase in molar volume may cause decrease in
oxygen packing density and mass density.
The results of modulus of rigidity ‘η’ of the lithium
cadmium phosphate glasses are listed in Table 2 and are
depicted graphically in Figure 7 as a function of Lithium
Oxide concentration. The results show that ‘η’ decreases
with increasing amount of Li2O. The decrease in
modulus of rigidity may be due to decrease in oxygen
packing density [10,12], which is a consequence of in-
creasing number of non-bridging oxygen due to which

M. ALTAF ET AL.
204
Table 2. Variation of Modulus of rigidity, transition temperature softening temperature and coefficient of linear thermal
expansion with respect to glass comp os ition in mole%.
Modulus Rigidity η (dy/ cm2) × 1011
Composition Mole %
Li2O-CdO-P2O5 Unannealed samples Annealed samples
Transition Temperature
Tg (˚C)
Softening Temperature Ts
(˚C)
Coefficient Of linear
Expasion α (˚C)-1
0%-50%-50% 3.29 3.42 387 555 8.99
05%-45%-50% 3.17 3.19 350 490 9.52
10%-40%-50% 2.95 2.97 342 465 10.24
15%-35%-50% 2.78 2.82 330 445 11.11
20%-30%-50% 2.40 2.68 322 433 11.93
25%-25%-50% 2.63 2.57 315 425 12.70
30%-20%-50% 2.16 2.51 ----- ----- -----
Figure 7. Dependence of modulus of rigidity on lithium
oxide concentration.
the glass structure has further expanded.
The linear thermal expansion of these glasses is de-
picted in a representative Figure 2. The estimated values
of transition temperature Tg, softening temperature Ts
and calculated values of coefficient of linear thermal
expansion are listed in Table 2 and are depicted in Fig-
ures 8 and 9 respectively. Tg and Ts show a decreasing
trend while coefficient of linear expansion increases with
increasing concentration of Li2O. In ternary lithium
cadmium phosphate glasses a high coordination number
modifier/intermediate is being replaced by a low coordi-
nation number modifier Li2O [2,14]. The intermediate
oxide CdO probably becomes the part of structure along
with the glass former P2O5. The modifiers do not con-
tribute to the network formation but essentially settle as
interstices in the glass structure. The addition of alkali
metal oxide cleaves the structure and disturbs the bond-
ing between glass forming cations and oxygen anions.
Figure 8. Graph illustrating the variation of Transition and
Softening temperatures with the variation of lithium oxide
concentration.
Figure 9. Variation of coefficient of linear expansion with
respect to Li2O concentration.

M. ALTAF ET AL.
205
This increase, the number of non-bridging oxygens
and thus develop a more open structure. Consequently
the structure expands the molar volume which causes a
decrease in the oxygen packing density and hence a de-
crease in the density of the glass sample. The decrease in
oxygen packing density along with the decrease of den-
sity and increase of molar volume of these glasses make
them less mechanical resistive which may have caused
an increase in the coefficient of linear expansion and
decrease in the transition temperature and the softening
temperature. The results reported here are similar to
those reported by other research workers [13,15-17].
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