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Raman study of B2O3–SrO–CuO glasses
Vibrational Spectroscopy 29 (2002) 241±244
Raman study of B2O3±SrO±CuO glasses D. Maniua,*, T. Iliescua, I. Ardeleana, R. Ciceo-Lucacela, M. Bolboacab, W. Kieferb b
a Babes-Bolyai University, Physics Department, M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania Institut fuÈr Physikalische Chemie, UniversitaÈt WuÈrzburg, Am Hubland, D-97074 WuÈrzburg, Germany
Received 31 August 2001; received in revised form 5 December 2001; accepted 5 December 2001
Abstract The in¯uence of copper oxide (CuO) content on the structure of 3B2O3SrO glass was investigated by means of Raman spectroscopy. For the sample without CuO, the Raman spectrum indicates a structure with majority pentaborate groups. At high wavenumbers, there is a broad and intense band probably due to ¯uorescence induced by strontium. The addition of CuO in 3B2O3SrO glass causes changes in the features of the Raman spectra. When CuO content rises the Raman band corresponding to boroxol units becomes higher than the one characteristic to pentaborate groups. The ¯uorescence band decreases in intensity and vanishes for x 0:03. The structure of glasses with low CuO content contains pentaborate groups, boroxol rings, orthoborate groups, chain-type metaborate groups and diborate groups. For high CuO content the number of pentaborate groups decreases, orthoborate and diborate groups disappear and pyroborate groups are formed. Therefore, we conclude that the copper ions act as network modi®er in these glasses. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Spectroscopy; Borate glasses; Structure; Raman spectra
1. Introduction Most glasses are formed by mixing glass-forming oxides (SiO2, B2O3, P2O3, etc.) with modi®er metal oxide [1]. The oxygen from the metal oxide becomes part of the covalent glass network by creating new structural units [2,3]. Raman spectroscopy becomes an effective tool for resolving the structure of local arrangements in glasses. Raman spectra and identi®cation of glass forming structural units in borate glasses were also analysed by other authors [4,5]. The introduction of the third element in the glasses leads to the changes in the glass structure, metal oxide acting as modi®er [6±8]. * Corresponding author. E-mail address: [email protected] (D. Maniu).
In this paper, the structural units from xCuO(1 x)[3B2O3SrO] glasses with different molar concentration of copper oxide (CuO) (0 x 0:35) were investigated by means of Raman spectroscopy. 2. Experimental The glasses were obtained by mixing H3BO3, SrCO3 and CuO in suitable proportion and by mixture in sintered corundum crucibles at T 1150 8C for 0.5 h. The samples were obtained by pouring the melts in stainless steel forms. These glasses are hygroscopic and therefore special care has to be taken to protect them from hydrolysis (i.e. a thin ®lm of special oil cover the surface of the glasses). We measured Raman spectra of same sample at different time and did not
0924-2031/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 4 - 2 0 3 1 ( 0 1 ) 0 0 1 8 4 - 9
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D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
observe any changes. The light scattering was collected from the inner of the glass. In order to obtain Raman spectra the 514.4 nm line of an Ar-ion laser (Spectra Physics model 2016) was used. The plasma lines were avoided by means of a ®lter prism (Anaspec) and the laser beam was focused on the sample with an Olympus microscope objective (Olympus ULWD 80, NA 0.75). The back-scattered light was collected by the same objective and was focused on the entrance slit of the spectrometer. A Dilor XY Raman triple monochromator with a Peltier cooled, intensi®ed array with 1024 diodes was employed as the light detection system. The backscattering con®guration allows the observation of the sample before light exposure. The laser power was 400 mW. The measurements were carried out at room temperature. The spectral data are processed using Dilor and specially developed software. A frequency calibration was performed. The spectra were recorded with a resolution of 2 cm 1 and spectral data were analysed with XMGR software. 3. Results and discussions Raman spectra of xCuO(1 x)[3B2O3SrO] glasses with various contents of CuO (0 x 0:35) are given in Figs. 1 and 2. The following bands are present in these spectra: 470, 670, 770, 800, 930, 960, 1050, 1350, and 1450 cm 1. In the spectra with low CuO content a broad and intense band situated at high wavenumbers occurs. The dominant band in the Raman spectra of vitreous B2O3 is at 806 cm 1. This band was assigned to the boroxol ring oxygen breathing vibration involving a very little boron motion (boron atom coordinate is 3) [9]. (A list of borate groups found in borate compounds is given by Meera et al. [5]). The addition of a modi®er oxide determines the appearance of a strong band at 770 cm 1 and the shift of the 806 cm 1 band to lower wavenumbers (800 cm 1) [5]. Bril [10] assigned the 770 cm 1 Raman band to the symmetric breathing vibration of six membered rings with one BO4 tetrahedron (i.e. triborate, tetraborate or pentaborate). The lower wavenumber band (755 cm 1) was assigned to the symmetric breathing vibration of six membered rings with two BO4 tetrahedra (i.e. diborate, ditriborate or dipentaborate) [10].
Fig. 1. Raman spectra of xCuO(1 0 x 0:01.
x)[3B2O3SrO] glasses with
Because the 770 cm 1 band appears in the presented Raman spectra and the 755 cm 1 band does not appear, we conclude that our glasses contain six membered rings with one BO4 tetrahedron. Since it is not possible to distinguish which units are present only by taking into account this band, additional information has to be added. Crystalline a- and bK2O±5B2O3, which contain only pentaborate units, give Raman bands at 765 and 885 cm 1 and at 785 and 925 cm 1, respectively [11]. Crystalline Na2O±4B2O3 (consisting of tetraborate groups) and crystalline Cs2O±3B2O3 (consisting of triborate groups) have
D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
Fig. 2. Raman spectra of xCuO(1 0:03 x 0:35.
x)[3B2O3SrO] glasses with
only a very weak signal in the 900 cm 1 region [11]. Thus, the 770 cm 1 band together with 930 cm 1 band can be considered as an indication of the presence of pentaborate groups in the studied glasses. For the Raman spectra with CuO (0 x 0:1), the 770 and 800 cm 1 bands rise above the other Raman bands, the intensity of the 770 cm 1 band being higher than that of the 800 cm 1 band. Thus, we conclude that pentaborate groups and boroxol rings dominate the structure of the studied glasses. The number of pentaborate groups is higher than the number of boroxol rings. This result is supported by the difference in intensity of the characteristic bands (the cross section of this two borate groups are very similar). For CuO (x > 0:2), the intensity of the 770 cm 1 band
243
decreases. This fact involves the decreasing of the number of pentaborate units with increasing the CuO content. This behaviour can be explained through the transformation of pentaborate units in another borate units when many copper atoms are connected in the glass network. At low CuO content the 930 cm 1 band appears as a shoulder of the 960 cm 1 band. This band decreases in intensity when the concentration of CuO rises and for x 0:03 it turns into a shoulder of 930 cm 1 band. Crystalline lithium and magnesium orthoborates exhibit a strong peak in the 950 cm 1 region [12,13]. Therefore, the 960 cm 1 band can be attributed to orthoborate groups. The behaviour of the 960 cm 1 band indicates the presence of orthoborate groups in the structure of the studied glasses only at low content of CuO (x 0:03). For CuO (0 x 0:01), we can observe a small band centred at 1050 cm 1. In borate glasses, this band has been attributed to the presence of diborate groups [14]. It does not appear in the Raman spectra of glasses with high content of CuO. Therefore, we can presume that the glasses with high content of CuO do not contain diborate groups. For all studied spectra, the 670 and 470 cm 1 bands also appear. The 660±670 cm 1 band is assigned to metaborate units [5], while the 470 cm 1 band is attributed to a ring angle bending (B±O±B) from borate units [15]. The intensity of 470 cm 1 band slowly increases when the CuO content increases. For low CuO content the observed spectra present a broad and intense band, probably due to the ¯uorescence induced by strontium. The intensity of this band decreases when CuO content increases. For high CuO content, this band disappears and the characteristic borate bands are present. For x 0:03 a large Raman band is present at 1450 cm 1. This band indicates the presence of the chain-type metaborate groups [16]. Because the 670 cm 1 band (characteristic to metaborate groups) is present in all spectra and the 1450 cm 1 band appears at high CuO content, we consider that in the studied glasses metaborate groups are only of chain-type. We presume that the ¯uorescence band at low CuO content covered the 1450 cm 1 band. For CuO (x 0:35) the 1450 cm 1 band is not so clearly evidenced, but we observed a band at 1350 cm 1 assigned to the formation of pyroborate
244
D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
groups [17]. Therefore, we conclude that at high CuO content the pyroborate groups are formed. 4. Conclusions The addition of CuO in 3B2O3SrO glass causes changes in the features of the Raman spectra. The strontium ¯uorescence band decreases when CuO content rises and for x 0:03 vanishes. Raman spectra reveal Raman bands speci®c to borate groups such as chain type metaborate groups, pentaborate groups, boroxol rings, orthoborate groups, diborate groups, and pyroborate units. The main bands in the observed spectra are characteristic to boroxol units and pentaborate groups. When the CuO content increases the number of pentaborate groups decreases, orthoborate and diborate groups disappear and pyroborate groups are formed. Therefore, we conclude that the copper ions act as network modi®er in the studied glasses. Acknowledgements M. Bolboaca and W. Kiefer acknowledge ®nancial support from the German Science Foundation and the Fonds der Chemischen Industrie.
References [1] M. Scagliotti, M. Villa, G. Geiodelli, J. Non-Cryst. Solids 93 (1987) 350. [2] K. Terashima, S.-H. Kim, T. Yako, J. Am. Ceram. Soc. 78 (6) (1995) 1601. [3] E.I. Kamitsos, A.P. Patsis, G.D. Chryssikos, J. Non-Cryst. Solids 152 (1993) 246. [4] E.I. Kamitsos, G.D. Chryssikos, J. Mol. Struct. 247 (1991) 1. [5] B.N. Meera, A.K. Sood, N. Chandrabhas, J. Ramakrishna, J. Non-Cryst. Solids 126 (1990) 224. [6] D. Maniu, I. Ardelean, T. Iliescu, J. Mater. Sci. Lett. 16 (1997) 19. [7] E.I. Kamitsos, M.A. Karakasides, G.D. Chryssikos, J. Phys. Chem. 91 (1987) 1073. [8] S. Suoto, M. Massot, M. Balkanski, Solid State Ion. 70/71 (1994) 350. [9] B.P. Dwivedi, M.H. Rahman, Y. Kumar, B.N. Knanna, J. Phys. Chem. Solids 54 (1993) 621. [10] T.W. Bril, Philips Res. Rep. Suppl. 2 (1976) 117. [11] W.L. Konijnendijk, Philips Res. Rep. Suppl. 1 (1975) 224. [12] E.I. Kamirtsos, M.A. Karakassides, Phys. Chem. Glasses 30 (1989) 19. [13] E.I. Kamirtsos, M.A. Karakassides, G.D. Chryssikos, J. Phys. Chem. 91 (1987) 1073. [14] J. Krong-Moe, Phys. Chem. Glasses 61 (1965) 46. [15] W.L. Konijnendijk, J.M. Stevels, Mater. Sci. Res. 12 (1977) 259. [16] T. Iliescu, S. Simon, D. Maniu, I. Ardelean J. Mol. Struct. 294 (1992) 201. [17] B.N. Meera, J. Ramakrishna, J. Non-Cryst. Solids 159 (1993) 1.
Raman study of B2O3±SrO±CuO glasses D. Maniua,*, T. Iliescua, I. Ardeleana, R. Ciceo-Lucacela, M. Bolboacab, W. Kieferb b
a Babes-Bolyai University, Physics Department, M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania Institut fuÈr Physikalische Chemie, UniversitaÈt WuÈrzburg, Am Hubland, D-97074 WuÈrzburg, Germany
Received 31 August 2001; received in revised form 5 December 2001; accepted 5 December 2001
Abstract The in¯uence of copper oxide (CuO) content on the structure of 3B2O3SrO glass was investigated by means of Raman spectroscopy. For the sample without CuO, the Raman spectrum indicates a structure with majority pentaborate groups. At high wavenumbers, there is a broad and intense band probably due to ¯uorescence induced by strontium. The addition of CuO in 3B2O3SrO glass causes changes in the features of the Raman spectra. When CuO content rises the Raman band corresponding to boroxol units becomes higher than the one characteristic to pentaborate groups. The ¯uorescence band decreases in intensity and vanishes for x 0:03. The structure of glasses with low CuO content contains pentaborate groups, boroxol rings, orthoborate groups, chain-type metaborate groups and diborate groups. For high CuO content the number of pentaborate groups decreases, orthoborate and diborate groups disappear and pyroborate groups are formed. Therefore, we conclude that the copper ions act as network modi®er in these glasses. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Spectroscopy; Borate glasses; Structure; Raman spectra
1. Introduction Most glasses are formed by mixing glass-forming oxides (SiO2, B2O3, P2O3, etc.) with modi®er metal oxide [1]. The oxygen from the metal oxide becomes part of the covalent glass network by creating new structural units [2,3]. Raman spectroscopy becomes an effective tool for resolving the structure of local arrangements in glasses. Raman spectra and identi®cation of glass forming structural units in borate glasses were also analysed by other authors [4,5]. The introduction of the third element in the glasses leads to the changes in the glass structure, metal oxide acting as modi®er [6±8]. * Corresponding author. E-mail address: [email protected] (D. Maniu).
In this paper, the structural units from xCuO(1 x)[3B2O3SrO] glasses with different molar concentration of copper oxide (CuO) (0 x 0:35) were investigated by means of Raman spectroscopy. 2. Experimental The glasses were obtained by mixing H3BO3, SrCO3 and CuO in suitable proportion and by mixture in sintered corundum crucibles at T 1150 8C for 0.5 h. The samples were obtained by pouring the melts in stainless steel forms. These glasses are hygroscopic and therefore special care has to be taken to protect them from hydrolysis (i.e. a thin ®lm of special oil cover the surface of the glasses). We measured Raman spectra of same sample at different time and did not
0924-2031/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 4 - 2 0 3 1 ( 0 1 ) 0 0 1 8 4 - 9
242
D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
observe any changes. The light scattering was collected from the inner of the glass. In order to obtain Raman spectra the 514.4 nm line of an Ar-ion laser (Spectra Physics model 2016) was used. The plasma lines were avoided by means of a ®lter prism (Anaspec) and the laser beam was focused on the sample with an Olympus microscope objective (Olympus ULWD 80, NA 0.75). The back-scattered light was collected by the same objective and was focused on the entrance slit of the spectrometer. A Dilor XY Raman triple monochromator with a Peltier cooled, intensi®ed array with 1024 diodes was employed as the light detection system. The backscattering con®guration allows the observation of the sample before light exposure. The laser power was 400 mW. The measurements were carried out at room temperature. The spectral data are processed using Dilor and specially developed software. A frequency calibration was performed. The spectra were recorded with a resolution of 2 cm 1 and spectral data were analysed with XMGR software. 3. Results and discussions Raman spectra of xCuO(1 x)[3B2O3SrO] glasses with various contents of CuO (0 x 0:35) are given in Figs. 1 and 2. The following bands are present in these spectra: 470, 670, 770, 800, 930, 960, 1050, 1350, and 1450 cm 1. In the spectra with low CuO content a broad and intense band situated at high wavenumbers occurs. The dominant band in the Raman spectra of vitreous B2O3 is at 806 cm 1. This band was assigned to the boroxol ring oxygen breathing vibration involving a very little boron motion (boron atom coordinate is 3) [9]. (A list of borate groups found in borate compounds is given by Meera et al. [5]). The addition of a modi®er oxide determines the appearance of a strong band at 770 cm 1 and the shift of the 806 cm 1 band to lower wavenumbers (800 cm 1) [5]. Bril [10] assigned the 770 cm 1 Raman band to the symmetric breathing vibration of six membered rings with one BO4 tetrahedron (i.e. triborate, tetraborate or pentaborate). The lower wavenumber band (755 cm 1) was assigned to the symmetric breathing vibration of six membered rings with two BO4 tetrahedra (i.e. diborate, ditriborate or dipentaborate) [10].
Fig. 1. Raman spectra of xCuO(1 0 x 0:01.
x)[3B2O3SrO] glasses with
Because the 770 cm 1 band appears in the presented Raman spectra and the 755 cm 1 band does not appear, we conclude that our glasses contain six membered rings with one BO4 tetrahedron. Since it is not possible to distinguish which units are present only by taking into account this band, additional information has to be added. Crystalline a- and bK2O±5B2O3, which contain only pentaborate units, give Raman bands at 765 and 885 cm 1 and at 785 and 925 cm 1, respectively [11]. Crystalline Na2O±4B2O3 (consisting of tetraborate groups) and crystalline Cs2O±3B2O3 (consisting of triborate groups) have
D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
Fig. 2. Raman spectra of xCuO(1 0:03 x 0:35.
x)[3B2O3SrO] glasses with
only a very weak signal in the 900 cm 1 region [11]. Thus, the 770 cm 1 band together with 930 cm 1 band can be considered as an indication of the presence of pentaborate groups in the studied glasses. For the Raman spectra with CuO (0 x 0:1), the 770 and 800 cm 1 bands rise above the other Raman bands, the intensity of the 770 cm 1 band being higher than that of the 800 cm 1 band. Thus, we conclude that pentaborate groups and boroxol rings dominate the structure of the studied glasses. The number of pentaborate groups is higher than the number of boroxol rings. This result is supported by the difference in intensity of the characteristic bands (the cross section of this two borate groups are very similar). For CuO (x > 0:2), the intensity of the 770 cm 1 band
243
decreases. This fact involves the decreasing of the number of pentaborate units with increasing the CuO content. This behaviour can be explained through the transformation of pentaborate units in another borate units when many copper atoms are connected in the glass network. At low CuO content the 930 cm 1 band appears as a shoulder of the 960 cm 1 band. This band decreases in intensity when the concentration of CuO rises and for x 0:03 it turns into a shoulder of 930 cm 1 band. Crystalline lithium and magnesium orthoborates exhibit a strong peak in the 950 cm 1 region [12,13]. Therefore, the 960 cm 1 band can be attributed to orthoborate groups. The behaviour of the 960 cm 1 band indicates the presence of orthoborate groups in the structure of the studied glasses only at low content of CuO (x 0:03). For CuO (0 x 0:01), we can observe a small band centred at 1050 cm 1. In borate glasses, this band has been attributed to the presence of diborate groups [14]. It does not appear in the Raman spectra of glasses with high content of CuO. Therefore, we can presume that the glasses with high content of CuO do not contain diborate groups. For all studied spectra, the 670 and 470 cm 1 bands also appear. The 660±670 cm 1 band is assigned to metaborate units [5], while the 470 cm 1 band is attributed to a ring angle bending (B±O±B) from borate units [15]. The intensity of 470 cm 1 band slowly increases when the CuO content increases. For low CuO content the observed spectra present a broad and intense band, probably due to the ¯uorescence induced by strontium. The intensity of this band decreases when CuO content increases. For high CuO content, this band disappears and the characteristic borate bands are present. For x 0:03 a large Raman band is present at 1450 cm 1. This band indicates the presence of the chain-type metaborate groups [16]. Because the 670 cm 1 band (characteristic to metaborate groups) is present in all spectra and the 1450 cm 1 band appears at high CuO content, we consider that in the studied glasses metaborate groups are only of chain-type. We presume that the ¯uorescence band at low CuO content covered the 1450 cm 1 band. For CuO (x 0:35) the 1450 cm 1 band is not so clearly evidenced, but we observed a band at 1350 cm 1 assigned to the formation of pyroborate
244
D. Maniu et al. / Vibrational Spectroscopy 29 (2002) 241±244
groups [17]. Therefore, we conclude that at high CuO content the pyroborate groups are formed. 4. Conclusions The addition of CuO in 3B2O3SrO glass causes changes in the features of the Raman spectra. The strontium ¯uorescence band decreases when CuO content rises and for x 0:03 vanishes. Raman spectra reveal Raman bands speci®c to borate groups such as chain type metaborate groups, pentaborate groups, boroxol rings, orthoborate groups, diborate groups, and pyroborate units. The main bands in the observed spectra are characteristic to boroxol units and pentaborate groups. When the CuO content increases the number of pentaborate groups decreases, orthoborate and diborate groups disappear and pyroborate groups are formed. Therefore, we conclude that the copper ions act as network modi®er in the studied glasses. Acknowledgements M. Bolboaca and W. Kiefer acknowledge ®nancial support from the German Science Foundation and the Fonds der Chemischen Industrie.
References [1] M. Scagliotti, M. Villa, G. Geiodelli, J. Non-Cryst. Solids 93 (1987) 350. [2] K. Terashima, S.-H. Kim, T. Yako, J. Am. Ceram. Soc. 78 (6) (1995) 1601. [3] E.I. Kamitsos, A.P. Patsis, G.D. Chryssikos, J. Non-Cryst. Solids 152 (1993) 246. [4] E.I. Kamitsos, G.D. Chryssikos, J. Mol. Struct. 247 (1991) 1. [5] B.N. Meera, A.K. Sood, N. Chandrabhas, J. Ramakrishna, J. Non-Cryst. Solids 126 (1990) 224. [6] D. Maniu, I. Ardelean, T. Iliescu, J. Mater. Sci. Lett. 16 (1997) 19. [7] E.I. Kamitsos, M.A. Karakasides, G.D. Chryssikos, J. Phys. Chem. 91 (1987) 1073. [8] S. Suoto, M. Massot, M. Balkanski, Solid State Ion. 70/71 (1994) 350. [9] B.P. Dwivedi, M.H. Rahman, Y. Kumar, B.N. Knanna, J. Phys. Chem. Solids 54 (1993) 621. [10] T.W. Bril, Philips Res. Rep. Suppl. 2 (1976) 117. [11] W.L. Konijnendijk, Philips Res. Rep. Suppl. 1 (1975) 224. [12] E.I. Kamirtsos, M.A. Karakassides, Phys. Chem. Glasses 30 (1989) 19. [13] E.I. Kamirtsos, M.A. Karakassides, G.D. Chryssikos, J. Phys. Chem. 91 (1987) 1073. [14] J. Krong-Moe, Phys. Chem. Glasses 61 (1965) 46. [15] W.L. Konijnendijk, J.M. Stevels, Mater. Sci. Res. 12 (1977) 259. [16] T. Iliescu, S. Simon, D. Maniu, I. Ardelean J. Mol. Struct. 294 (1992) 201. [17] B.N. Meera, J. Ramakrishna, J. Non-Cryst. Solids 159 (1993) 1.