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The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass
Materials Letters 64 (2010) 1025–1027
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass Shufeng Song, Zhaoyin Wen ⁎, Yu Liu CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 DingXi Road, Shanghai 200050, PR China
a r t i c l e
i n f o
Article history: Received 23 December 2009 Accepted 27 January 2010 Available online 1 February 2010 Keywords: Bi2O3 Thermal properties Structure Adhesion
a b s t r a c t The effect of substitution of Bi2O3 for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (Tg) and the FTIR results of the glasses indicated significant effect of Bi2O3 substitution on the glass structure, which caused a progressive conversion of BO3 to BO4 unit in the glass. The appropriate amount of Bi2O3 obviously improved the wetting performance of the borosilicate glass on Al2O3 substrate due to the high polarizability of Bi3+ ion. © 2010 Elsevier B.V. All rights reserved.
1. Introduction The borosilicate glasses are widely used due to their excellent properties like low thermal expansion coefficient (TEC) and perfect chemical durability [1]. The TEC is particularly significant in determining the fields of application [2]. Kitaigorodsky noted that the TEC of the glasses depended on their compositions, rising with the increase in alkali, lime and alumina, and falling with the increase of silica, boric oxide and zinc oxide content [3]. Sheen pointed out that a noticeable reduction in the TEC occurred while substituting titania for sodium oxide [4]. The sodium sulfur battery is one of the most promising candidates for energy storage technology developed since 1980s [5]. For both safety and performance reasons, the seal between the electrolyte beta-alumina and the insulator alpha-alumina is significant. The borosilicate glass is selected as sealant for the sodium sulfur battery due to its excellent chemical durability [6]. However, the borosilicate glass has inherent disadvantage like high melting temperature and sealing temperature, easy cristobalite precipitation, and poor thermal expansion match. The seal creates a major challenge in the development of the sodium sulfur battery. As has been reported by earlier works, the role of Bi3+ in glasses may best be compared with that of Pb2+ due to their similarity in atomic weight, ionic radius, and electronic configuration. Bi2O3 is a conditional glass former due to its high polarizability. Bi3+ may build the glass network of both BiO6 and BiO3 units in the presence of conventional glass-forming cations such as Si4+, B3+, P5+ and Ge4+ [7].
⁎ Corresponding author. Tel.: + 86 21 52411704; fax: + 86 21 52413903. E-mail address: [email protected] (Z. Wen). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.01.080
In this work, to extend the application of borosilicate glass, the thermal properties, structure and adhesion behavior of the Bi-doped borosilicate glasses were studied as a function of the substitution of Bi2O3 for alkali oxides. 2. Experimental Reagent grade SiO2, Al2O3, H3BO3, Na2CO3, K2CO3, Li2CO3, CeO2, CaF2, TiO2, ZrO2 and Bi2O3 were weighed according to their compositions listed in Table 1. The mixed raw powders were melted at 1400 °C for 4 h in a Pt crucible. Then the melts were poured into cold water. The specimens for TEC measurement were heated from room temperature to 700 °C at a heating rate of 5 °C/min on a dilatometer (NETZSCH DIL 402C). The glass transition temperature (Tg) and softening temperature (Ts) were determined from the thermal expansion curves. The Fourier transform infrared (FTIR) spectra measurements were made prepared in the form of KBr pellets pressed at 10 MPa. The chemical structure of the glasses was investigated with FTIR spectroscopy. The contact angle of the glass on polished Al2O3 substrate (96% of Al2O3, CeramTec, Germany) about 1 mm thickness was tested on a contact analyzer (Kruss, HTM 1700). 3. Results and discussion 3.1. Thermal behavior The effect of the substitution of Bi2O3 for R2O on the TEC of the glasses was shown in Fig. 1. It was obviously seen that the TEC strongly depended on the substitution. It decreased with the increasing Bi2O3 content. In addition, the variation of the TEC of the glasses was slight while R2O was completely replaced by Bi2O3. The
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S. Song et al. / Materials Letters 64 (2010) 1025–1027
Table 1 Compositions of the glass systems. Glass
G0 G1 G2 G3 G4
Compositions (wt.%) SiO2
Al2O3
B2O3
Na2O
K2O
Li2O
CeO2
CaF2
TiO2
ZrO2
Bi2O3
65.8 65.8 65.8 65.8 65.8
3.2 3.2 3.2 3.2 3.2
18.0 18.0 18.0 18.0 18.0
3.75 3.0 2.0 0 0
3.75 3.0 2.0 0 0
1.0 1.0 1.0 1.0 1.0
0.5 0.5 0.5 0.5 0.5
0.5 0.5 0.5 0.5 0.5
2.0 2.0 2.0 2.0 2.0
1.5 1.5 1.5 1.5 1.5
0 1.5 3.5 7.5 9.5
TEC of the glass was primarily correlated with the glass compositions and glass structure. Bi2O3 tends to form the bonds that are more covalent than that of R2O due to the higher electronegativity of Bi. Therefore, the substitution of Bi2O3 for R2O induced a decrease in the TEC of the glasses. The variation of the Tg and Ts was also shown in Fig. 1. As seen, the Tg decreased with the increasing Bi2O3 content, however, it increased while R2O was completely replaced by Bi2O3. It is known that Bi3+ is highly polarizable due to its large ionic radius, small cation field strength and a lone pair of valence shell. The electronic shell of O2− is influenced by the high polarization of Bi3+. Therefore, the increase of Bi2O3 content resulted in the increase of the non-bridging oxygens which in turn made the glass network loose. It is noticeable that the Tg increased while the R2O was completely replaced by Bi2O3. The reason would be that the role of Bi2O3 in the glass changed from the network modifier to former while the R2O was completely replaced by Bi2O3, which will be further proved by the following FTIR analysis. As seen in Fig. 1, the Ts also showed nonlinear variation relationship with Bi2O3 content. However, there was an overall increase in Ts with R2O replaced by Bi2O3, which would be ascribed to the replacement of weaker Na–O and K–O bonds by stronger Bi–O bond. It was interesting that the tendency of the variation of the Tg and Ts was not consistent, which indicated that the Tg and Ts depended on different factors in the investigated glasses. The Tg depended on the glass structure mainly, whereas, the Ts depended principally on the strength of chemical bonds.
Fig. 2. Infrared spectra of the studied glass systems.
and 603 cm− 1 arising in glasses G1–G4 are assigned to Bi–O− stretching vibration in BiO6 unit [10,11]. It was observed that the main bands of glasses G1–G3 were broader than that of basic glass G0, indicating that the glass network became looser while R2O was replaced by Bi2O3. However, the main bands of glass G4 became sharp, indicating the network former role of extra Bi2O3. Furthermore, the intensity of bands around 933 cm− 1 increased with the increasing Bi2O3 content, indicating that an increasing amount of BO4 unit with the substitution. Whereas, the intensity of bands around 1461 cm− 1 decreased with the increasing Bi2O3 content, indicating a decreasing amount of BO3 unit with the substitution. Therefore, it was indicated that the substitution of Bi2O3 for R2O caused a progressive conversion of BO3 to BO4 unit.
3.3. Wetting behavior
Fig. 2 illustrates the FTIR spectra of the studied glasses. The bands at about 460 and 1100 cm− 1 are attributed to the bending and stretching vibrations of Si–O–Si bond in SiO4 tetrahedron, respectively. The bands around 673 cm− 1 are attributed to the total vibration of BO3 and BO4 [8]. The bands at about 1390 and 1460 cm− 1, and 933 cm− 1 are attributed to the vibration of BO3, BO4 unit, respectively [9]. The bands at about 790 cm− 1 are attributed to the AlO4 unit. The weak bands at about 429
A good wettability is one of the key factors for a favorable adhesion. The wetting behavior of the glasses on Al2O3 substrate was investigated as a function of the substitution of Bi2O3 for R2O shown in Fig. 3. The contact angle of basic glass G0 was maintained 90° from 1000 to 1100 °C, it realized wetting on the Al2O3 substrate above 1100 °C. The wetting behavior of the substituted glasses on the Al2O3 substrate was better than that of basic glass G0, especially glass G1, displaying a contact angle of 60° at 1050 °C. As the FTIR analyzed above, the glass network became looser while R2O was replaced by Bi2O3 due to the high polarizability of Bi3+ ion. The looser glass network made the glass flow more readily and improved the wettability.
Fig. 1. TEC, Tg and Td vs. Bi2O3 contents of the investigated glasses.
Fig. 3. Contact angle of the glasses as a function of substitution of Bi2O3 for R2O.
3.2. FTIR spectra
S. Song et al. / Materials Letters 64 (2010) 1025–1027
4. Conclusions In this work, the effect of the substitution of Bi2O3 for R2O on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The TEC of the glasses decreased with the substitution due to the more covalent of Bi3+ than that of R+ ion. Bi2O3 acted as a network modifier in the substituted glass, however, extra Bi2O3 played a role of network former. Furthermore, the addition of Bi2O3 caused a progressive conversion of BO3 to BO4 unit. The appropriate amount of Bi2O3 obviously improved the wettability of the borosilicate glass on Al2O3 substrate. Acknowledgments This work was financially supported by NSFC Project No. 50730001, research projects of Chinese Science and Technology Ministry No. 2007BAA07B01 and No. 2007CB209700, and research Projects from the Science and Technology Commission of Shanghai Municipality No. 06DE12213, 07DE12004 and 08DZ2210900.
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References [1] Lima MM, Monteiro R. Characterisation and thermal behaviour of a borosilicate glass. Thermochim Acta 2001;373:69–74. [2] Park JH, Lee SJ. Mechanism of preventing crystallization in low-firing glass–ceramic composite substrates. J Am Ceram Soc 1995;78:1128–30. [3] Kitaigorodsky I, Rodin SV. The value of the thermal expansion factor of aluminium oxide in glass. J Soc Glass Technol 1928;12:164–9. [4] Gavriliu G. Thermal expansion and characteristic points of –Na2O–SiO2 glass with added oxides. J Eur Ceram Soc 2002;22:1375–9. [5] American Electric Power website. http://www.aep.com. [6] Sudworth JL, Tilley AR. Sodium Sulfur Battery. 2nd ed. New York: Cambridge; 1985. [7] Miyaji F, Sakka S. Structure of PbO–Bi2O3–Ga2O3 glasses. J Non-Cryst Solids 1991;134:77–85. [8] EI-Egili K. Infrared studies of Na2O–B2O3–SiO2 and Al2O3–Na2O–B2O3–SiO2 glasses. Physica B 2003;325:340–8. [9] Kamitsos EI, Patsis AP, Karakassides MA. Infrared reflectance spectra of lithium borate glasses. J Non-cryst Solids 1990;126:52–67. [10] Pascuta P, Culea E. FTIR spectroscopic study of some bismuth germanate glasses containing gadolinium ions. Mater Lett 2008;62:4127–9. [11] Dimitrov V, Dimitriev Y. IR-spectra and structure of V2O5–GeO2–Bi2O3 glasses. J Non-cryst Solids 1994;180:51–7.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass Shufeng Song, Zhaoyin Wen ⁎, Yu Liu CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 DingXi Road, Shanghai 200050, PR China
a r t i c l e
i n f o
Article history: Received 23 December 2009 Accepted 27 January 2010 Available online 1 February 2010 Keywords: Bi2O3 Thermal properties Structure Adhesion
a b s t r a c t The effect of substitution of Bi2O3 for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (Tg) and the FTIR results of the glasses indicated significant effect of Bi2O3 substitution on the glass structure, which caused a progressive conversion of BO3 to BO4 unit in the glass. The appropriate amount of Bi2O3 obviously improved the wetting performance of the borosilicate glass on Al2O3 substrate due to the high polarizability of Bi3+ ion. © 2010 Elsevier B.V. All rights reserved.
1. Introduction The borosilicate glasses are widely used due to their excellent properties like low thermal expansion coefficient (TEC) and perfect chemical durability [1]. The TEC is particularly significant in determining the fields of application [2]. Kitaigorodsky noted that the TEC of the glasses depended on their compositions, rising with the increase in alkali, lime and alumina, and falling with the increase of silica, boric oxide and zinc oxide content [3]. Sheen pointed out that a noticeable reduction in the TEC occurred while substituting titania for sodium oxide [4]. The sodium sulfur battery is one of the most promising candidates for energy storage technology developed since 1980s [5]. For both safety and performance reasons, the seal between the electrolyte beta-alumina and the insulator alpha-alumina is significant. The borosilicate glass is selected as sealant for the sodium sulfur battery due to its excellent chemical durability [6]. However, the borosilicate glass has inherent disadvantage like high melting temperature and sealing temperature, easy cristobalite precipitation, and poor thermal expansion match. The seal creates a major challenge in the development of the sodium sulfur battery. As has been reported by earlier works, the role of Bi3+ in glasses may best be compared with that of Pb2+ due to their similarity in atomic weight, ionic radius, and electronic configuration. Bi2O3 is a conditional glass former due to its high polarizability. Bi3+ may build the glass network of both BiO6 and BiO3 units in the presence of conventional glass-forming cations such as Si4+, B3+, P5+ and Ge4+ [7].
⁎ Corresponding author. Tel.: + 86 21 52411704; fax: + 86 21 52413903. E-mail address: [email protected] (Z. Wen). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.01.080
In this work, to extend the application of borosilicate glass, the thermal properties, structure and adhesion behavior of the Bi-doped borosilicate glasses were studied as a function of the substitution of Bi2O3 for alkali oxides. 2. Experimental Reagent grade SiO2, Al2O3, H3BO3, Na2CO3, K2CO3, Li2CO3, CeO2, CaF2, TiO2, ZrO2 and Bi2O3 were weighed according to their compositions listed in Table 1. The mixed raw powders were melted at 1400 °C for 4 h in a Pt crucible. Then the melts were poured into cold water. The specimens for TEC measurement were heated from room temperature to 700 °C at a heating rate of 5 °C/min on a dilatometer (NETZSCH DIL 402C). The glass transition temperature (Tg) and softening temperature (Ts) were determined from the thermal expansion curves. The Fourier transform infrared (FTIR) spectra measurements were made prepared in the form of KBr pellets pressed at 10 MPa. The chemical structure of the glasses was investigated with FTIR spectroscopy. The contact angle of the glass on polished Al2O3 substrate (96% of Al2O3, CeramTec, Germany) about 1 mm thickness was tested on a contact analyzer (Kruss, HTM 1700). 3. Results and discussion 3.1. Thermal behavior The effect of the substitution of Bi2O3 for R2O on the TEC of the glasses was shown in Fig. 1. It was obviously seen that the TEC strongly depended on the substitution. It decreased with the increasing Bi2O3 content. In addition, the variation of the TEC of the glasses was slight while R2O was completely replaced by Bi2O3. The
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S. Song et al. / Materials Letters 64 (2010) 1025–1027
Table 1 Compositions of the glass systems. Glass
G0 G1 G2 G3 G4
Compositions (wt.%) SiO2
Al2O3
B2O3
Na2O
K2O
Li2O
CeO2
CaF2
TiO2
ZrO2
Bi2O3
65.8 65.8 65.8 65.8 65.8
3.2 3.2 3.2 3.2 3.2
18.0 18.0 18.0 18.0 18.0
3.75 3.0 2.0 0 0
3.75 3.0 2.0 0 0
1.0 1.0 1.0 1.0 1.0
0.5 0.5 0.5 0.5 0.5
0.5 0.5 0.5 0.5 0.5
2.0 2.0 2.0 2.0 2.0
1.5 1.5 1.5 1.5 1.5
0 1.5 3.5 7.5 9.5
TEC of the glass was primarily correlated with the glass compositions and glass structure. Bi2O3 tends to form the bonds that are more covalent than that of R2O due to the higher electronegativity of Bi. Therefore, the substitution of Bi2O3 for R2O induced a decrease in the TEC of the glasses. The variation of the Tg and Ts was also shown in Fig. 1. As seen, the Tg decreased with the increasing Bi2O3 content, however, it increased while R2O was completely replaced by Bi2O3. It is known that Bi3+ is highly polarizable due to its large ionic radius, small cation field strength and a lone pair of valence shell. The electronic shell of O2− is influenced by the high polarization of Bi3+. Therefore, the increase of Bi2O3 content resulted in the increase of the non-bridging oxygens which in turn made the glass network loose. It is noticeable that the Tg increased while the R2O was completely replaced by Bi2O3. The reason would be that the role of Bi2O3 in the glass changed from the network modifier to former while the R2O was completely replaced by Bi2O3, which will be further proved by the following FTIR analysis. As seen in Fig. 1, the Ts also showed nonlinear variation relationship with Bi2O3 content. However, there was an overall increase in Ts with R2O replaced by Bi2O3, which would be ascribed to the replacement of weaker Na–O and K–O bonds by stronger Bi–O bond. It was interesting that the tendency of the variation of the Tg and Ts was not consistent, which indicated that the Tg and Ts depended on different factors in the investigated glasses. The Tg depended on the glass structure mainly, whereas, the Ts depended principally on the strength of chemical bonds.
Fig. 2. Infrared spectra of the studied glass systems.
and 603 cm− 1 arising in glasses G1–G4 are assigned to Bi–O− stretching vibration in BiO6 unit [10,11]. It was observed that the main bands of glasses G1–G3 were broader than that of basic glass G0, indicating that the glass network became looser while R2O was replaced by Bi2O3. However, the main bands of glass G4 became sharp, indicating the network former role of extra Bi2O3. Furthermore, the intensity of bands around 933 cm− 1 increased with the increasing Bi2O3 content, indicating that an increasing amount of BO4 unit with the substitution. Whereas, the intensity of bands around 1461 cm− 1 decreased with the increasing Bi2O3 content, indicating a decreasing amount of BO3 unit with the substitution. Therefore, it was indicated that the substitution of Bi2O3 for R2O caused a progressive conversion of BO3 to BO4 unit.
3.3. Wetting behavior
Fig. 2 illustrates the FTIR spectra of the studied glasses. The bands at about 460 and 1100 cm− 1 are attributed to the bending and stretching vibrations of Si–O–Si bond in SiO4 tetrahedron, respectively. The bands around 673 cm− 1 are attributed to the total vibration of BO3 and BO4 [8]. The bands at about 1390 and 1460 cm− 1, and 933 cm− 1 are attributed to the vibration of BO3, BO4 unit, respectively [9]. The bands at about 790 cm− 1 are attributed to the AlO4 unit. The weak bands at about 429
A good wettability is one of the key factors for a favorable adhesion. The wetting behavior of the glasses on Al2O3 substrate was investigated as a function of the substitution of Bi2O3 for R2O shown in Fig. 3. The contact angle of basic glass G0 was maintained 90° from 1000 to 1100 °C, it realized wetting on the Al2O3 substrate above 1100 °C. The wetting behavior of the substituted glasses on the Al2O3 substrate was better than that of basic glass G0, especially glass G1, displaying a contact angle of 60° at 1050 °C. As the FTIR analyzed above, the glass network became looser while R2O was replaced by Bi2O3 due to the high polarizability of Bi3+ ion. The looser glass network made the glass flow more readily and improved the wettability.
Fig. 1. TEC, Tg and Td vs. Bi2O3 contents of the investigated glasses.
Fig. 3. Contact angle of the glasses as a function of substitution of Bi2O3 for R2O.
3.2. FTIR spectra
S. Song et al. / Materials Letters 64 (2010) 1025–1027
4. Conclusions In this work, the effect of the substitution of Bi2O3 for R2O on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The TEC of the glasses decreased with the substitution due to the more covalent of Bi3+ than that of R+ ion. Bi2O3 acted as a network modifier in the substituted glass, however, extra Bi2O3 played a role of network former. Furthermore, the addition of Bi2O3 caused a progressive conversion of BO3 to BO4 unit. The appropriate amount of Bi2O3 obviously improved the wettability of the borosilicate glass on Al2O3 substrate. Acknowledgments This work was financially supported by NSFC Project No. 50730001, research projects of Chinese Science and Technology Ministry No. 2007BAA07B01 and No. 2007CB209700, and research Projects from the Science and Technology Commission of Shanghai Municipality No. 06DE12213, 07DE12004 and 08DZ2210900.
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References [1] Lima MM, Monteiro R. Characterisation and thermal behaviour of a borosilicate glass. Thermochim Acta 2001;373:69–74. [2] Park JH, Lee SJ. Mechanism of preventing crystallization in low-firing glass–ceramic composite substrates. J Am Ceram Soc 1995;78:1128–30. [3] Kitaigorodsky I, Rodin SV. The value of the thermal expansion factor of aluminium oxide in glass. J Soc Glass Technol 1928;12:164–9. [4] Gavriliu G. Thermal expansion and characteristic points of –Na2O–SiO2 glass with added oxides. J Eur Ceram Soc 2002;22:1375–9. [5] American Electric Power website. http://www.aep.com. [6] Sudworth JL, Tilley AR. Sodium Sulfur Battery. 2nd ed. New York: Cambridge; 1985. [7] Miyaji F, Sakka S. Structure of PbO–Bi2O3–Ga2O3 glasses. J Non-Cryst Solids 1991;134:77–85. [8] EI-Egili K. Infrared studies of Na2O–B2O3–SiO2 and Al2O3–Na2O–B2O3–SiO2 glasses. Physica B 2003;325:340–8. [9] Kamitsos EI, Patsis AP, Karakassides MA. Infrared reflectance spectra of lithium borate glasses. J Non-cryst Solids 1990;126:52–67. [10] Pascuta P, Culea E. FTIR spectroscopic study of some bismuth germanate glasses containing gadolinium ions. Mater Lett 2008;62:4127–9. [11] Dimitrov V, Dimitriev Y. IR-spectra and structure of V2O5–GeO2–Bi2O3 glasses. J Non-cryst Solids 1994;180:51–7.