Paper
Journal of the Ceramic Society of Japan 120 [11] 530-533 2012
Effect of Nb 2 O 5 addition to SnO–P 2 O 5 glass
Satoshi FUKUI, Shinichi SAKIDA,*,³ Yasuhiko BENINO and Tokuro NANBA
Graduate School of Environmental and Life Science, Okayama University,
3–1–1 Tsushima-naka, Kita-ku, Okayama 700–8530, Japan
*Environmental Management Center, Okayama University,
3–1–1 Tsushima-naka, Kita-ku, Okayama 700–8530, Japan
SnO­P2O5 glasses have high refractive index and low glass transition temperature but have poor water durability. To improve
water durability, NbO2.5 was added to SnO­P2O5 glasses, preparing SnO­NbO2.5­P2O5 glass. It was found that addition of only
4 mol % NbO2.5 was enough to achieve significant improvement of water durability, and at the same time, no degradation in
thermal and optical properties was observed.
©2012 The Ceramic Society of Japan. All rights reserved.
Key-words : SnO–P2O5 glass, Nb2O5, Glass transition temperature, Refractive index, Water durability
[Received June 1, 2012; Accepted October 2, 2012]
1.
Introduction
SnO­P2O5 (SP) glasses have interesting features, such as
significantly low glass transition temperature and high refractive
index, and SnO is considered as an alternative to PbO due to the
similarity in various properties.1) Hence SP glasses have been
expected to be used as optical glass,2) sealing glass,3) anode
materials for lithium-ion secondary batteries.4) Nevertheless, the
low chemical durability of phosphate glasses often limits the
practical use of SP glasses.
It is expected that the water durability is improved by the
addition of the third component. Generally, Al2O3, Fe2O3 and
B2O3 are effective to improve water durability,5)­7) but they also
lead to the deterioration in properties.
It is known that Nb2O5-containg glasses show high refractive
index,7),8) good transparency8) and good non-linear optical properties.9) In this work, Nb2O5 was added to SP glasses, and thermal
and optical properties and water durability of SnO­NbO2.5­P2O5
(SNP) glass were evaluated. At the same time, various properties
of SNP glasses were compared with other phosphate glasses.
2.
2.1
Experimental procedure
Sample preparation
SNP glasses were prepared from starting materials of
NH4H2PO4, SnO and Nb2O5. Compositions of the samples
prepared are shown in Fig. 1, where Nb2O5 is indicated as
NbO2.5. At the start of this study, SnO in a 65SnO­35P2O5 glass
was replaced with Nb2O5, and hence NbO2.5 instead of Nb2O5
was used to keep the total number of cations in the glasses constant. The glass batches were melted at 1100°C for 30 min in an
alumina crucible under Ar atmosphere. Ar atmosphere provided a
reducing atmosphere to inhibit the oxidation of Sn2+ to Sn4+
during melting. The glass melts were quenched on a steel mold
heated at glass transition temperature (Tg) of corresponding
glasses. The glasses were finally annealed at Tg for 1 h to remove
strain and prevent crack formation, obtaining the specimens.
³
Corresponding author: S. Sakida; E-mail: [email protected].
ac.jp
530
(Color online) Glass forming region of the ternary SnO­
NbO2.5­P2O5 system.
Fig. 1.
2.2
Evaluation
Glass composition was examined by X-ray fluorescence (XRF)
spectrometry. Tg was determined from differential thermal
analysis (DTA) operated at a heating rate of 10 K/min. Density
was measured in kerosene with Archimedes method. Refractive
indexes of nd and nD at the wavelengths of 587.6 nm (d-line) and
589.3 nm (D1-line) were measured by means of a prism coupler
method. Abbe number ¯D = (nd ¹ 1)/(nF ¹ nC) was determined,
where nF and nC are the refractive indexes at 486.1 nm (F-line)
and 656.3 nm (C-line), respectively. The transmittance of the
glasses was measured by a UV­Vis-NIR spectrophotometer at a
wavelength range from 190 to 2500 nm.
The immersion test was carried out by using the MCC-1
method to evaluate the water durability of glass palates with
12 © 10 © 1 mm. Optically polished glass sample was immersed
in 200 ml of water for 72 h at 70°C. After the immersion, the
sample was dried and weighed. Dissolution rate (DR) was
calculated from the measured weight loss ("W), sample surface
area (S), time of immersion (t), by using the following equation:
DR = ¦W (kg)/S (m2)/t (s).
©2012 The Ceramic Society of Japan
JCS-Japan
Journal of the Ceramic Society of Japan 120 [11] 530-533 2012
Table 1. Glass transition temperature Tg, density μ and dissolution rate DR of 65SnO­xNbO2.5­(35­x)P2O5 glasses and
other phosphate glasses
Glass composition
Tg (°C)
μ (g/cm3)
DR [kg/(m2·s)]
References
65S0N35P (x = 0)
65S1N34P (x = 1)
65S2N33P (x = 2)
65S3N32P (x = 3)
65S4N31P (x = 4)
65S5N30P (x = 5)
60S40P
62S38P
65S35P
67S33P
70S30P
72S28P
66.7SnO­4B2O3­29.3P2O5
45SnO­15MnO­40P2O5
60PbO40P2O5
270
280
285
292
299
316
241, 300
261
256
268­274
265
279
300
332
349
3.747
3.762
3.795
3.822
3.846
3.878
3.517­3.763
3.63
3.904
3.722­3.91
3.96­4.117
4.05
3.85
3.49
5.47
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12)
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13)
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Fig. 2. (Color online) Photographs of SNP glasses. (a) 50S5N45P, (b)
55S5N40P, (c) 60S5N35P, (d) 65S5N30P, (e) 70S5N25P, (f ) 60S10N30P,
(g) 55S20N25P, (h) 60S15N25P (i) 65S10N25P.
3.
3.1
Results
Glass formation ranges and coloration
Figure 1 shows the glass forming region of the ternary SnO­
NbO2.5­P2O5 system. The compositional region obtaining the
glasses without crystallization is P2O5 = 25­45 mol %, SnO =
50­70 mol % and NbO2.5 are 0­25 mol %. According to XRF
analysis, compositional fluctuation was observed, where the
volatilization of SnO and incorporation of Al2O3 were suggested.
The compositional deviation was less than 2 mol %, which was
not systematic against the batch composition. Then, the nominal
compositions are used in the following results.
Figure 2 shows the visual appearance of SNP glasses. All the
glass samples containing NbO2.5 are colored yellow, dark blue
or green which is dependent on the composition. As shown in
Figs. 2(d), 2(g) and 2(h), 65SnO­5NbO2.5­30P2O5 (denoted as
65S5N35P), 55S20Nb25P and 60S15N25P glasses are colored
yellow but transparent. The coloration seems to be originated
from the composition of tin pyrophosphate (Sn2P2O7), that is, the
glasses with SnO/P2O5 < 2 are colored dark blue and those with
SnO/P2O5 > 2 are yellowish. 60S10N30P glass which is located
on the boundary is colored green [Fig. 2(f )].
3.2
Effect of NbO2.5 addition on the various
properties
As shown in Fig. 2(d), the transparency of 65S5N30P glass is
the highest among the glasses given in Fig. 2. Then, the change
in color was examined with reducing NbO2.5 content from the
Fig. 3.
(Color online) Photographs
of
65SnO­xNbO2.5­(35­x)P2O5
glasses.
composition of 65S5N30P, in which the glass composition
was given as 65SnO­·xNbO2.5­(35­x)P2O5 [65SxN(35­x)P, x =
0­5 mol %].
Figure 3 shows the visual appearance of 65SxN(35­x)P
glasses. As the amount of NbO2.5 decreases, the yellow color
gradually fades.
Tg and density of 65SxN(35­x)P glasses are summarized in
Table 1, in which the data of some phosphates are also listed for
comparison. By adding NbO2.5, Tg of SNP glasses monotonically
increases, but Tg remains lower than 320°C at x < 5 mol %,
indicating that SNP glasses maintain the characteristics in lowglass transition properties of SP glasses.
The results of immersion test (DR) are also shown in Table 1.
With increasing NbO2.5 content, DR gradually decreases, and in
the glasses of 65S4N31P and 65S5N30P weight loss is not
observed. It is therefore suggested that the minute addition of
NbO2.5 is very effective to improve water durability of SP glasses.
Table 2 summarizes the optical properties of SNP glasses.
Along with NbO2.5 addition, the refractive index and dispersion
increase gradually. Figure 4 shows the transmission spectra of
SNP glasses. Regardless of Nb2O5 content, the transmittance at
visible light region is about 70­80%. As shown in Table 2, the
absorption edge shifts longer wavelength side by the addition of
531
JCS-Japan
Fukui et al.: Effect of Nb2O5 addition to SnO–P2O5 glass
Table 2. Refractive index nd and nD, Abbe number vd and absorption edge ­e of 65SnO­xNbO2.5­(35­x)P2O5 glasses and
other phosphate glasses
Fig. 4.
Glass composition
nd
nD
vd
­e (nm)
References
65S0N35P
65S1N34P
65S2N33P
65S3N32P
65S4N31P
65S5N30P
60S40P
62S38P
65S35P
67S33P
70S30P
72S28P
45S­15MnO­40P
66.7S­33.3P + 0­8Er2O3
25Pb75P
30Pb70P
1.750
1.765
1.786
1.802
1.813
1.825
1.741
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1.745
1.759
1.780
1.795
1.806
1.800
1.7486
1.762
1.7794
1.792­1.794
1.8332
1.822
1.80­1.85
1.78­1.81
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25.7
24.8
23.4
22.9
22.3
22.2
24.66, 27.0
45.6
23.33
41.5
20.40
38.0
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364
383
390
395
396
310
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11), 15)
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14)
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5)
5)
Transmission spectra of 65SnO­xNbO2.5­(35­x)P2O5 glasses.
NbO2.5. In comparison with other phosphate glasses, SNP glasses
have absorption edge at longer wavelength. A large red shift of
absorption edge is confirmed between x = 0 and 1, and with
further addition of NbO2.5, however, the shift is quite small. In a
strontium barium niobate, (Sr, Ba)Nb2O6 crystal, the absorption
edge is observed at 370 nm, which is due to the charge transfer
from oxide ion to Nb5+ ion.17) It is consequently concluded that
the absorption beginning at around 400 nm is caused by Nb5+
ions present in SNP glasses. The deeper coloration of dark blue
or green is probably due to Nb ions with lower valency, such
as Nb4+. As mentioned, the glass batches were melted under
Ar atmosphere to prevent the oxidation of Sn2+ to Sn4+, and it
is hence supposed that some Nb5+ ions are reduced to Nb4+,
resulting in the deeper coloration. Optical absorption of Nb ions
in lower oxidation numbers has never been reported, and it
is hence difficult to estimate the amount of reduced Nb ions
based on absorption spectrometry. If the reduced Nb ions are
responsible for the deeper coloration, the reduction of Nb ions
seems to be suppressed in the less-colored glasses with SnO/
P2O5 ratio µ 2. However, the reason remains obscure because the
valency of Nb ions is dependent on the various factors, such as
melting temperature, oxygen partial pressure, coexisting chemical
species and basicity of glass matrix. Further experiments are
required to clarify the coloration of the present glasses.
532
Fig. 5. Raman spectra of 65SnO­xNbO2.5­(35­x)P2O5 glasses and
Sn2P2O7 crystal.
4. Discussion
The improvement of water durability will be discussed based
on the glass structure. It is known that Sn2P2O7 crystal has high
water durability,18) where the crystal consists of dimers of PO4
tetrahedra with Q1 structure. Figure 5 shows the Raman spectra
of SNP glasses and Sn2P2O7 crystal. The bands at 1050 and
743 cm¹1 are assigned to P­O stretching of non-bridging and
bridging oxygens in Q1 species, respectively, and the 980 cm¹1
band is due to P­O stretching of non-bridging oxygens in Q0
species.6) With increasing NbO2.5 content, the similarity in
Raman spectra between the glasses and crystal slightly decreases.
At the same time, an additional peak is confirmed at 830 cm¹1,
which is associated with NbO6 octahedra.9),19) Growth of the
830 cm¹1 peak indicates the increase in the number of Nb­O
bonds. Nb­O bonds (0.20 nm)20) are shorter than Sn­O bonds
(0.22 nm),21) indicating that Nb­O bonds are stronger than Sn­O
bonds. It is also reported that the addition of Nb2O5 into phosphate glasses results in the strengthening of glass networks.22)
JCS-Japan
Journal of the Ceramic Society of Japan 120 [11] 530-533 2012
The increase in concentration of Nb­O bonds should result in the
reinforcement of glass frameworks, providing the improvement
of water durability. As shown in Table 1, Tg increases with
increasing NbO2.5 content. which also suggests the reinforcement
of glass structure. The structure in Sn2P2O7 crystal has high
resistance to water, and NbO2.5 addition leads to incorporation of
Nb­O bonds into Sn2P2O7 structure, constructing more waterdurable structure.
5.
Conclusion
NbO2.5 was added to SnO­P2O5 glass to improve water
durability, and thermal and optical properties were examined.
• Glass formation range of SnO­NbO2.5­P2O5 system was
determined. Due to NbO2.5 addition, the glasses were colored,
and it was suggested that the coloration was dependent on
SnO/P2O5 molar ratio.
• Even in the small amount of NbO2.5 addition, significant
improvement of water durability was achieved without
degradation in optical and thermal properties. The glass
frameworks consisted of the dimers of PO4 units, and
Sn ions tightly connected the dimers. Incorporation of stronger
Nb­O bonds strengthened the glass frameworks, improving
water durability.
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
References
1)
2)
3)
4)
5)
S. Chenu, R. Lebullenger and J. Rocherulle, J. Mater. Sci., 45,
6505­6510 (2010).
H. Takebe, W. Nonaka, T. Kubo, J. Cha and M. Kuwabara,
J. Phys. Chem. Solids, 68, 983­986 (2007).
R. Morena, J. Non-Cryst. Solids, 263–264, 382­387 (2010).
A. Hayashi, T. Konishi, K. Tadanaga, T. Minami and M.
Tatsumisago, J. Non-Cryst. Solids, 345–346, 478­483 (2004).
L. M. Sharaf El-Deen, M. S. Al Salhi and M. M. Elkholy,
J. Non-Cryst. Solids, 354, 3762­3766 (2008).
20)
21)
22)
J. W. Lim, M. L. Schmitt, R. K. Brow and S. W. Yung, J. NonCryst. Solids, 356, 1279­1384 (2010).
Z. Teixeira, O. L. Alves and I. O. Mazali, J. Am. Ceram. Soc.,
90, 256­263 (2007).
F. F. Sena, J. R. Martinelli and L. Gomes, J. Non-Cryst. Solids,
348, 63­71 (2004).
T. Hayakawa, M. Hayakawa, M. Nogami and P. Thomas, Opt.
Mater., 32, 448­455 (2010).
D. Holland, A. P. Howes, M. E. Smith and A. C. Hannon,
J. Phys.: Condens. Matter, 14, 13609­13621 (2002).
J. W. Lim, S. W. Yung and R. K. Brow, J. Non-Cryst. Solids,
357, 2690­2694 (2011).
J. Cha, T. Kubo, H. Takebe and M. Kuwabara, J. Ceram. Soc.
Japan, 68, 983­986 (2007).
V. Dimitrov and T. Komatsu, J. Non-Cryst. Solids, 249, 160­
179 (1999).
W. J. Chung, J. Choi and Y. G. Choi, J. Alloys Compd., 505,
661­667 (2010).
D. Ehit, J. Non-Cryst. Solids, 354, 546­552 (2008).
J. J. Shyu and C. C. Chiang, J. Am. Ceram. Soc., 93, 2720­
2725 (2010).
M. Gao, S. Kapphan, S. Porcher and R. Pankrath, J. Phys.:
Condens. Matter, 11, 4913­4924 (1999).
N. Hemono, S. Chenu, R. Lebullenger, J. Rocherulle, V.
Keryvin and A. Wattiaux, J. Mater. Sci., 45, 2916­2920
(2010).
S. M. Hsu, J. J. Wu, T. S. Chin, T. Zhang, Y. M. Lee, C. M.
Chu and J. Y. Ding, J. Non-Cryst. Solids, 358, 14­19 (2012).
D. Munoz-Martin, A. Ruiz de La Cruz, J. M. FernandezNavarro, C. Domingo, J. Solis and J. Gonzalo, J. Appl. Phys.,
110, 023522 (2011).
V. V. Chernaya, A. S. Mitiaev, P. S. Chizhov, E. V. Dikarev,
R. V. Shpanchenko, E. V. Antipov, M. V. Korolenko and P. B.
Fabritchinyi, J. Chem. Mater, 17, 284­290 (2005).
V. L. Mamoshin, N. N. Batalov, G. V. Zelyutin, E. A. Kozyreva
and A. M. Nepomiluev, Glass and Ceramics, 55, 299­302
(1998).
533