Full text of DOI:10.1557/JMR.2002.0287

Structural and optical properties of lithium
bismuthate glasses
A. Pan and A. Ghosha)
Department of Solid State Physics, Indian Association for the Cultivation of Science,
Kolkata 700032, India
(Received 7 November 2001; accepted 6 May 2002)
Structural and optical properties of ion-conducting lithium bismuthate glasses are
reported here. The structure of these glasses has been explored from the compositional
variation of the density, molar volume, and glass transition temperature. The optical
study in the visible and infrared region indicates a large transmission window for these
glasses. The BiO6 octahedra were identified as the main structural unit from the
Raman spectra of these bismuthate glasses.
I. INTRODUCTION
alkali-metal tellurite glasses and their crystalline coun-
terparts indicated a change in the coordination of the
tellurium atom from TeO4 trigonal bipyramids through
TeO3+1 polyhedra to TeO3 trigonal pyramids. However,
the study of the physical properties of the ionic glasses
formed with a heavy metal oxide such as Bi2O3 has been
paid little attention. These glasses are interesting from
the application point of view as they can be used as layers
for optical and optoelectronic devices, thermal and me-
chanical sensors, reflecting windows, etc.24–29 Recent
structural studies of lithium alkaline earth bismuthate
glasses30 showed the presence of distorted BiO6 octahe-
dra as the main structural unit. At lower Li2O content,
Li+ ions go into the structural interstices to compensate
the excess negative charge of BiO6 octahedra. At higher
Li2O content, however, the charge compensation is ex-
ceeded and a few relatively strong Bi–O bonds are re-
placed by weak Li+–O− bonds.
A considerable attention has been paid for a few de-
cades to study the properties of ionic glasses formed with
glass formers such as SiO2, P2O5, B2O3, TeO2, etc. The
local structure of sodium in a glassy silicate network
was explored using EXAFS.1 The modified random net-
work model was proposed to explain the ion dynamics
in these glasses.2,3 It was observed that the introduction
of metal oxides in phosphate glasses leads to a depoly-
merization of the P–O–P network,4 which was con-
firmed by 31P MASNMR.5,6 X-ray photoelectron
spectroscopy analysis was used to determine the ratio of
the bridging oxygen to the terminal sites for phosphate
glasses.6–8 The NMR,9–13 Raman,14,15 Infrared (IR) ab-
sorption,11,16 neutron diffraction,17 etc., results supported
that the introduction of a network modifier in borate
glasses resulted in a progressive increase in the number
of four-coordinated boron atoms at the expense of three-
coordinated boron atoms. Krogh-Moe18 explored the
structural change in sodium and lithium borate glasses by
assuming the network in the short-range order to be built
up of the same structural units as those existed in the
crystalline counterparts. In the case of tellurite glasses,
earlier x-ray diffraction (XRD) studies19,20 revealed a
coordination number for tellurium atom as 6. The IR
study of the tellurite glasses and the polycrystalline com-
pounds confirmed the analogy in the short-range order
between vitreous and crystalline counterparts.21 The neu-
tron diffraction studies22 of tellurite glasses contradict
the earlier XRD studies and asserted the coordination
number of tellurium as 4. The Raman study23 of binary
In this paper, we report some structural and the optical
properties of the Li2O–Bi2O3 glasses.
II. EXPERIMENT
The lithium bismuthate glasses of compositions
x Li2O–(100 − x) Bi2O3, where x ס 14.3, 22.7, 26.7,
30.5, 39.8, 44.4, and 54.3, were prepared using melt
quenching technique. An appropriate amount of the re-
agent grade chemicals Bi2O3 and Li2CO3 (Aldrich
Chem. Co. Inc., WI, 99+%) was thoroughly mixed and
calcined at 450 °C for 2 h. The mixtures were then
melted in alumina crucibles in the temperature range
850–900 °C for about 1 h in air, in an electric furnace.
The quenching of the melt was done either in between
two copper plates or in a twin-roller. Transparent and
yellowish glass samples were obtained. The glassy nature
was confirmed from the XRD patterns. The prepared
a)Address all correspondence to this author.
e-mail: sspag@mahendra.iacs.res.in
J. Mater. Res., Vol. 17, No. 8, Aug 2002
© 2002 Materials Research Society
1941
http://journals.cambridge.org
Downloaded: 19 Apr 2015
IP address: 203.64.11.45

A. Pan et al.: Structural and optical properties of lithium bismuthate glasses
glass samples were annealed in another furnace at 200 °C
to remove residual stresses. The final glass compositions
were estimated from the atomic absorption analysis. The
densities were measured at room temperature by the liq-
uid displacement method using acetone as the immersion
liquid. The molar volumes were calculated from the den-
sity and compositions. Differential thermal analysis
(DTA) traces of the powdered samples were recorded in
a differential thermal analyzer (Shimadzu, DT40, Kyoto,
Japan) with a heating rate of 20 °C/min. The FT-IR spec-
tra of the glass samples were taken at room temperature
in a spectrophotometer (Magna IR-750, Series II, Nico-
let, Madison, WI) in the wave number range 400–
4000 cm−1. The ultraviolet–visible (UV–vis) spectra for
all compositions were recorded at room temperature in a
UV–vis scanning spectrometer (Shimazdu, model UV-
2101 PC, Kyoto, Japan) in the wavelength range 200–
700 nm. Stokes-shifted Raman spectra were recorded at
room temperature in the wave number range 10–
800 cm−1. This was achieved by means of a SPEX 1403
model (NJ) double monochromator at 4-cm−1 resolution
using an argon-ion laser (Spectra Physics, model 2020-05,
CA) for excitation at 488.0 or 514.5 nm, with a power
of 250 mW.
III. RESULTS AND DISCUSSION
The compositional variation of density (␳) and molar
volume (Vm) for the prepared glasses is shown in Fig. 1.
The molar volume (Vc) for the ideal close packing is also
plotted in the same figure. Vc was calculated by summing
up the molar volumes of crystalline Bi2O3 (52.36 cm3)
and Li2O (14.84 cm3) in suitable molar ratio. It can be
seen that the experimental molar volume (Vm) is always
greater than that of their hypothetical mixed crystalline
phases. These results clearly suggest an introduction of
the excess structural volume by the increasing Li2O com-
ponent at the expense of decreasing Bi2O3 component in
the glass compositions. This result is conducive for the
transport properties, in particular conductivity enhance-
ment, which is related to the available free volume within
the glass matrix for the movement of the ion.31
The DTA trace for a composition of lithium bis-
muthate glasses is shown in Fig. 2, which indicates an
endothermic glass transition and an exothermic crystal-
lization. The other compositions also showed similar
traces. The composition dependence of the glass transi-
tion temperature, Tg, calculated from the DTA trace is
shown in the inset. It has been reported that Tg is strictly
related to the density of cross-linking, the tightness of
packing in the network, the coordination of network
formers, etc.32,33 Therefore, it is suggested that the de-
crease of Tg with an increase of Li2O content is due to the
decrease in the density of cross-linking of the bismuthate
network. Thus, Bi–O–Bi cross-linkages are broken to
FIG. 1. Composition dependence of (a) the density (ᮀ) and (b) the
crystalline (᭺) and the glassy (ᮀ) molar volumes for x Li2O–(100 − x)
Bi2O3 glasses.
form nonbridging oxygen in the glasses. This result is in
conformity with the results of the composition depend-
ence of the molar volume (Fig. 1). The difference
between glass transition temperature Tg and the crystal-
lization temperature Tc is also very large (approximately
50 °C), indicating a good stability of these glasses.
Figure 3 shows the optical spectra of all the composi-
tions in the UV–vis region. A distinct cutoff has been
observed for all the compositions. The cutoff wave-
lengths do not vary much with composition (Table I).
The Fourier transform infrared (FTIR) spectrum for a
typical glass composition is shown in Fig. 4. Other glass
compositions also showed similar behavior. It is ob-
served that all these glasses exhibit a good transparency
up to 9–12 ␮m depending upon composition. An absorp-
tion band near 3400 cm−1 is observed due to water ad-
sorbed in the powdered samples. Strong and sharp
absorption bands occurring between 850 and 1100 cm−1
1942
J. Mater. Res., Vol. 17, No. 8, Aug 2002
http://journals.cambridge.org
Downloaded: 19 Apr 2015
IP address: 203.64.11.45

A. Pan et al.: Structural and optical properties of lithium bismuthate glasses
2−
are ascribed to the CO3 dissolved in the glasses, the
source of which is Li2CO3, used as the starting material
for glass preparation. The cutoff wavelengths in the UV
and IR regions are shown in Table I, which indicates a
large transmission window for all glass compositions.
The Raman spectra for different glass compositions
are shown in Fig. 5. The spectra consist of broad peaks
in the wave number range 80–800 cm−1. This broaden-
ing of the peaks is due to the disorder nature of the
samples. The superimposed broad peaks of the spectra
were deconvoluted into five peaks using a Gaussian dis-
tribution to find out the exact mode of vibrations. The
deconvoluted spectra for the glass composition 26.7
Li2O–73.3 Bi2O3 are shown in Fig. 5 by the solid curves.
The spectra for other compositions were also deconvo-
luted similarly. The values of the deconvoluted peak
wave numbers may be classified into three main sets: (i)
heavy metal ion vibration at 110–140 cm−1; (ii) bridging
anion modes at 300–600 cm−1; (iii) nonbridging anion
modes at 60–700 cm−1.
The low-frequency vibration mode at 100–140 cm−1
can be marked out for all the glasses and is assigned to
the vibration of Bi heavy metal.34 Although the band at
approximately 200 cm−1 cannot be associated with any
of the vibration, the Raman band in the region 300–
600 cm−1 is assigned to the symmetric stretching of an-
ion motion (i.e., vibration of bridging oxygen) in
TABLE I. Cutoff wavelengths in the UV and IR regions for x Li2O–
(100 − x) Bi2O3 glasses.
x
␭c(UV) (nm)
␭c(IR) (␮m)
(mol%)
( 0.01)
( 0.01)
FIG. 2. Differential thermal analysis curve for the 14.3 Li2O–85.7
Bi2O3 glass composition. Tg is shown by ꢀ. The inset shows the
variation of Tg with Li2O content.
14.3
22.7
26.7
30.5
39.8
44.4
54.3
440.0
455.0
455.0
430.0
433.0
405.0
410.0
10.1
9.5
8.8
10.1
10.4
11.6
9.3
FIG. 3. Optical spectra at room temperature for x Li2O–(100 − x)
Bi2O3 glass compositions in the UV–vis region: (a) x ס 14.3; (b) x ס
22.7; (c) x ס 26.7; (d) x ס 30.5; (e) x ס 39.8; (f) x ס 44.4; (g)
x ס 54.3.
FIG. 4. FT-IR spectrum at room temperature of the 26.7 Li2O–73.3
Bi2O3 glass composition.
J. Mater. Res., Vol. 17, No. 8, Aug 2002
1943
http://journals.cambridge.org
Downloaded: 19 Apr 2015
IP address: 203.64.11.45

A. Pan et al.: Structural and optical properties of lithium bismuthate glasses
REFERENCES
1. G.N. Greaves, A. Fontaine, P. Lagarde, D. Raoux, and S.J. Gurman,
Nature 293, 611 (1981).
2. G.N. Greaves and K.L. Ngai, in Defects in Insulating Materials,
edited by O. Kanert and J.M. Spaeth (World Scientific, Singapore,
1993), p. 53.
3. G.N. Greaves and K.L. Ngai, J. Non-Cryst. Solids 172–174, 1378
(1994).
4. J.R. Van Wazer, in Phosphorus and its Compounds (Interscience,
New York, 1958), Vol. 1, p. 717.
5. P. Losso, B. Schnabel, C. Jager, U. Sternberg, D. Stachel, and
D.O. Smith, J. Non-Cryst. Solids 143, 265 (1992).
6. R.K. Brow, D.R. Tallant, J.J. Hudgens, S.W. Martin, and
A.D. Irwin, J. Non-Cryst. Solids 177, 221 (1994).
7. R. Bruckner, H.U. Chun, H. Goretzki, and M. Sammet, J. Non-
Cryst. Solids 42, 49 (1980).
8. R. Gresch, W. Muller-Warmuth, and H. Dutz, J. Non-Cryst.
Solids 34, 127 (1979).
9. G.E. Jellison, Jr., and P.J. Bray, J. Non-Cryst. Solids 29, 187
(1978).
10. S.A. Feller, W.J. Dell, and P.J. Bray, J. Non-Cryst. Solids 51, 21
(1982).
11. C. Chiodelli, A. Magistris, M. Villa, and J.L. Bjorkstam, J. Non-
Cryst. Solids 51, 143 (1982).
12. K.S. Kim and P.J. Bray, J. Non-Cryst. Solids 2, 95 (1974).
13. S. Hayashi and K. Hayamizu, J. Non-Cryst. Solids 11, 214 (1989).
14. F. Galeener, G. Lucovsky, and J.C. Mikkelson, Jr., Phys. Rev. B
22, 3983 (1980).
FIG. 5. Raman spectra of x Li2O–(100 − x) Bi2O3 glass at room
temperature for different compositions: (a) x ס 14.3; (b) x ס 22.7; (c)
x ס 26.7; (d) x ס 30.5. The solid curves are the deconvoluted peaks
using a Gaussian distribution for the 26.7 Li2O–73.3 Bi2O3 glass com-
position.
15. J. Lorosch, M. Couzi, J. Pelous, R. Vacher, and A. Levasseur,
J. Non-Cryst. Solids 69, 1 (1984).
angularly constrained Bi–O–Bi configuration. The broad
and strong band at 380 and 500 cm−1 can be attributed to
the Bi–O–Bi vibration of the BiO6 unit.35 The shoulder at
600 cm−1, which sharpens with increasing Li2O content, is
due to Bi–O− stretching vibration of BiO6 unit modified by
Li2O. The sharpening of the shoulder at 600 cm−1 and a
decrease in intensity of the broad peak at approximately
380 cm−1 with increasing Li2O content indicate the breakage
of the Bi–O–Bi cross-linkage, which is supported by the com-
position dependence of molar volume and Tg (Figs. 1 and 2).
16. E.I. Kamitsos, A.P. Patsis, M.A. Karakassides, and
G.D. Chryssikos, J. Non-Cryst. Solids 126, 52 (1990).
17. J. Swenson, L. Borjesson, and W.S. Howells, Phys. Rev. B 52,
9310 (1995).
18. J. Krogh-Moe, Phys. Chem. Glasses 6, 46 (1965).
19. G.W. Brady, J. Chem. Phys. 24, 477 (1956).
20. G.W. Brady, J. Chem. Phys. 27, 300 (1957).
21. I.N. Morozova and A.K. Yakhind, Fiz. Khim. Stekla. 3, 197
(1977).
22. S. Neov, V. Kozhukharov, I. Gerasimova, K. Krezhov, and
V. Sidzhimov, J. Phys. C: Solid State Phys. 12, 2475 (1979).
23. T. Sekiya, N. Mochida, A. Ohtsuka, and M. Tonokawa, J. Non-
Cryst. Solids 144, 128 (1992).
IV. CONCLUSIONS
24. F. Borsa, D.R. Torgesson, S.W. Martin, and H.K. Patel, Phys.
Rev. B 46, 795 (1992).
25. Y. Dimitriev, V. Mihanilov, and E. Gattif, Phys. Chem. Glasses
34, 114 (1986).
26. W. Mianxue and Z. Peinan, J. Non-Cryst. Solids 84, 344 (1986).
27. Y. Takahashi and K. Yamaguchi, J. Mater. Sci. 25, 3950 (1990).
28. H. Zheng and J.D. Mackenzie, Phys. Rev. B 38, 7166 (1988);
H. Zheng, R. Xu, and J.D. Mackenzie, J. Mater. Res. 4, 911
(1989).
29. M. Onisi, M. Kyoto, and M. Watanabe, Jpn. J. Appl. Phys. 30,
L988 (1991).
30. J. Fu, Phys. Chem. Glasses 37, 84 (1996); 36, 211 (1995); J. Non-
Cryst. Solids 194, 207 (1996).
The compositional variation of density and molar vol-
ume of the present bismuthate glasses shows that an ex-
cess structural volume is introduced in Bi2O3 network by
the modifier Li2O. The glass transition temperature de-
creases with increasing Li2O content due to the formation
of nonbridging oxygen. A sharp cutoff has been observed
both in the UV and IR regions for all the compositions.
The deconvoluted peaks in the Raman spectra indicate
that the BiO6 octahedra are the main structural units in
the lithium bismuthate glasses.
31. J. Swenson and L. Bo¨rjesson, Phys. Rev. Lett. 77, 3569 (1996).
32. N.H. Ray, J. Non-Cryst. Solids 15, 423 (1974).
33. J.E. Shelby, J. Non-Cryst. Solids 46, 193 (1975).
34. A.A. Kharlamov, R.M. Almeida, and J. Heo, J. Non-Cryst. Solids
202, 233 (1996).
ACKNOWLEDGMENTS
A.P. acknowledges the Council of Scientific and In-
dustrial Research (India) for providing partial financial
assistance. The help offered by Dr. M. Ghosh, Depart-
ment of Spectroscopy, in taking Raman measurements is
also thankfully acknowledged.
35. R. Iordonova, Y. Dimitreiv, V. Dimitrov, S. Kassabox, and
D. Klissurski, J. Non-Cryst. Solids 204, 141 (1996).
1944
J. Mater. Res., Vol. 17, No. 8, Aug 2002
http://journals.cambridge.org
Downloaded: 19 Apr 2015
IP address: 203.64.11.45