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Connection between fictive temperature and structural defects responsible for the relaxational processes in oxide glasses
Journal of Non-Crystalline Solids 235±237 (1998) 388±392
Connection between ®ctive temperature and structural defects responsible for the relaxational processes in oxide glasses J.L Prat, F. Terki *, J. Pelous Laboratoire des Verres, UMR 5587, Universit e Montpellier II Place Eug ene Bataillon, case 069, 34095 Montpellier cedex, France
Abstract Raman spectra have been investigated in the 3±1500 cmÿ1 range in two sodium oxide phosphosilicate glasses with diering ®ctive temperatures, Tf . The temperature dependence of the spectra has been measured from lower temperatures to the glass transition temperature, Tg . Up to Tg the Bose-factor rescaled spectra coincide, but a dynamical quasielastic contribution depending on Tf , was observed in a large range of temperature. Relaxational processes related to a structural reordering are observed near Tg . A connection between Tf and medium range order deduced from inelastic light scattering in this frequency range is emphasized. This study point out that the quasielastic scattered intensity originates from thermally activated structural entities related to the disorder. Ó 1998 Elsevier Science B.V. All rights reserved. PACS: 78.35.+c; 78.30.-j; 78.30.Ly
1. Introduction
2. Sample preparation and experimental set up
The eect of quenching on the low frequency dynamics of glasses have stimulated a widespread interest and a lengthening list of experiments [1± 5]. In the present paper, we consider the cooling rate aect on the dynamics of glasses both below and above the glass transition temperature, Tg . Therefore the temperature dependence of the Raman spectra has been measured from low temperature up to Tg . This work coupled both Raman and Brillouin investigations from 10 GHz to 45 THz for two glasses stabilized in the temperature transition range at two dierent temperatures. The question we pose is how do relaxational processes relate to medium range order?
Two phosphosilicate specimens of molar composition Na2 O : 2Si O2 : 3:2P2 O5 were synthetised. They were stabilized at two dierent temperatures: 400°C and 600°C in the glass transition temperature range, and quickly cooled. They have two ®ctive temperatures, Tf . In the following the samples with a Tf of about 400°C and 600°C are labelled PHOS400 and PHOS600, respectively. Further details on the chemical preparation condition are discussed elsewhere [6]. In both Brillouin and Raman experiments the samples were illuminated with a single mode ion laser at k 514.5 nm (Spectra 2020) and a power intensity near 200 mW for low temperature investigations and 1W for high temperature ones. Brillouin scattering measurements were performed by a tandem six-pass Fabry±Perot spectrometer [7]. The details of the spectrometer conditions are
* Corresponding author. Tel.: +33 4 6714 4780; fax: +33 4 6714 3498; e-mail: [email protected].
0022-3093/98/$19.00 Ó 1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 0 9 3 ( 9 8 ) 0 0 6 5 4 - 1
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
described elsewhere [8]. The position and the linewidth of the Brillouin bands were obtained by a ®t using a convolution of the apparatus function (elastic line) with a theoretical shape derived from hypersonic velocity measurements. Besides, the half Brillouin linewidth, C, is related to the spatial acoustic attenuation, `ÿ1 (`ÿ1 4pC/V). Stokes and anti-Stokes Raman spectra were measured on a conventional triple-pass grating spectrometer (Coderg T800) with a resolution of about 1 cmÿ1 (1 cmÿ1 30 GHz). Moreover, for analyzing the very low-frequency Raman scattering we have applied a double-grating single-pass monochromator (SOPRA DMSP) [9]. This experimental device is
389
especially designed for higher resolution and lower frequency light scattering studies. It covers the frequency range between the Fabry±Perot experiment and the conventional Raman spectrometer with a resolution of about 6 GHz. 3. Results The aect of the ®ctive temperature in the very frequency range 0.4±6 cmÿ1 using Brillouin and Raman scattering measurements is shown in Fig. 1. An example of very low-frequency Raman spectra obtained for sample PHOS600 at three
Fig. 1. Brillouin and low-frequency Raman scattering measurements. (a) Example of very low-frequency Raman spectra in the PHOS600 using the SOPRA DMSP2000 spectrometer. (b) Raman reduced intensity for PHOS600 vs. temperature for several frequencies near the elastic line. (c) Longitudinal attenuation measured in PHOS400 and PHOS600 vs. temperature. The errors bars correspond to the accuracy of the experimental data for the attenuation (5%). (d) Raman scattering intensity at 2 cmÿ1 vs. temperature for the two phosphosilicate glasses. For comparison, the insert presents the hypersonic attenuation temperature variations for PHOS600. For clarity, we decide to report the errors bars only on Fig. 1(c) since the accuracy of the inelastic intensity is the same (5%).
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J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
temperatures is presented (Fig. 1(a)). From these measurements we deduce the quasielastic temperature dependence, Iqe (T), for several frequencies near the elastic line (Fig. 1(b)). Note that the intensity of Iqe (T) increases with the frequency in agreement with the expected increase of the atten-
uation at high frequency. The comparison with the temperature dependence of attenuation (insert of Fig. 1(d)) is in better accordance if we consider the extracted Iqe at the lowest frequency. Indeed the observed plateau in the C T dependence is also marked in Iqe (T) at 2 cmÿ1 and begins to dis-
Fig. 2. In¯uence of the ®ctive temperature on the Raman scattering temperature dependence for temperature sets below, near and above the glass transition temperature. Below the glass temperature transition: (a) T 150 K; (b) T 300 K and (c) T 630 K. Near and above the glass transition of the PHOS400 glass (Tg 673 K): (d) T 677 K, (e) T 777 K and (f) T 800 K. Near and above the glass transition of the PHOS600 glass (Tg 833 K): (g) T 835 K, (h) T 930 K and (i) T 980 K. Thick and thin solid lines represent reduced Raman scattering intensity of the PHOS400 and PHOS600, respectively.
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
appear at higher frequencies. The results presented in Fig. 1(c) indicate that, at the lower temperature, no ®ctive temperature eect on the scattered intensity is observed while for temperature greater than 300 K a Tf eect is detected. So, we conclude that thermal activation produces ®ctive temperature dierences. Moreover Fig. 1(d) shows a qualitative agreement between the Iqe (T) and C T dependence. Fig. 2 illustrates the aect of Tf on the Raman scattering temperature dependence for a set of temperatures, less than, within the glass transition temperature and greater than Tg . Dierences are noted in the glass transition temperature range of the two samples whereas at temperatures less than and greater than Tg the spectra are superimposed. So, at lower temperatures sample properties are not modi®ed by the temperature at which they have been stabilized. Moreover, the heat annealing memory is lost at temperatures greater than Tg . Note that in the equilibrium frozen liquid, a band at 160 cmÿ1 is observed in the two samples underlying a structural reordering such as a crystallization process. 4. Discussion The temperature dependence of the quasielastic intensity, Iqe (T), at frequencies near those used in the Brillouin measurements are indicative of an analogy with that of the acoustical attenuation, C T . Therefore, the predicted hypothesis [10,11] of a common physical origin of the phonon attenuation and the light scattered intensity within a temperature range across the glass temperature transition is detected from 300 K to 1000 K as found in other glasses [12,13]. The intensity of the relaxational modes are increased by increasing the quenching temperature. Nevertheless, at T 6 150 K the dierences are less and completely disappear at 20 K. Besides, we found that at T < 300 K the correlation between C T and Iqe (T) disappears which may be due to dierent activated processes for these two properties. In fact, this observed eect could be explained by the presence of defects dierently coupled to the disorder. Some of them contribute to the acoustical attenu-
391
ation and do not interact with the photons while other local entities actively scatter the light without aect on the acoustic modes. This idea has already been suggested in a recent work in lowtemperature studies [14,15]. Moreover, interesting features are revealed by quasielastic intensity frequency dependence in the glass transition temperature intervals. It is accepted that elastic intensity point out structural reordering since the viscosity eects start near Tg . Otherwise, this study at various step in the glass transition temperature range emphasizes that Raman scattering detects structural reordering at the nanometer scale. 5. Conclusion This study reveals several important points which could be summarized as following. The ®ctive temperature aects the acoustic attenuation and is related to the aect on the quasielastic intensity within a temperature range across the glass transition. However, at temperatures, 6 150 K the aect of the ®ctive temperature on both the acoustic attenuation and the low-frequency Raman intensity disappears. This disappearance leads to the existence of relaxational processes connected with acoustic modes as suggested for the explanation of the origin of the acoustical attenuation [16]. In the samples at high temperature an increase of relaxational defects are observed. These thermally activated processes disappear at lowtemperatures. Consequently at low-temperature the quasielastic intensity decreases whatever the ®ctive temperature. On another hand, we emphasize that inelastic scattering is aected by structural modi®cations occurring at temperatures in the glass transition range. References [1] R. Vacher, M. Delsanti, J. Pelous, L. Cecchi, A. Winter, J. Zarzycky, J. Mater. Sci. 9 (1974) 829. [2] V.K. Malinovsky, V.N. Novikov, A.P. Sokolov, Phys. Lett. A 70 (1987) 19. [3] L. Borjesson, A.K. Hassan, J. Swenson, L.M. Torell, A. Fontana, Phys. Rev. Lett. 70 (1993) 1275.
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J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
[4] M. Kr uger, M. Solwisch, I. Petscherizin, D. Quitmann, J. Chem. Phys. 96 (1992) 7352. [5] S.L. Isakov, S.N. Ishmaev, V.K. Malinovsky, V.N. Novikov, P.P. Parshing, S.N. Popov, A.P. Sokolov, M.G. Zemlyanov, Physica A 201 (1993) 386. [6] J.L. Prat, PhD thesis, Montpellier University, 1996. [7] R. Vacher, J. Pelous, Phys. Rev. B 14 (1976) 823. [8] F. Terki, C. Levelut, M. Boissier, J. Pelous, Phys. Rev. B 53 (1996) 2411. [9] V. Mazzacurati, P. Besnassi, G. Ruocco, J. Phys. E 21 (1988) 798. [10] J. Jackle, Amorphous solids, in: W.A. Phillips (Ed.), LowTemperature Properties, Topics in Current Physics, vol. 24, Springer, Berlin.
[11] V.L. Gurevich, D. Parshin, J. Pelous, H.R. Schober, Phys. Rev. B 48 (1993) 16318. [12] C. Levelut, N. Gaimes, F. Terki, G. Cohen-Solal, J. Pelous, R. Vacher, Phys. Rev. B 51 (1995) 8606. [13] F. Terki, C. Levelut, J-L. Prat, M. Boissier, J. Pelous, J. Phys.: Condens. Matter. 8 (1996) 941. [14] J.L. Prat, F. Terki, J. Pelous, Phys. Rev. Lett. 7 (1996) 755. [15] F. Terki, J.L. Prat, J. Pelous, Philos. Mag. B 77 (2) (1998) 373. [16] D. Tielb urger, K. Merz, R. Ehrenfeld, S. Hunklinger, Phys. Rev. B 45 (1992) 2750.
Connection between ®ctive temperature and structural defects responsible for the relaxational processes in oxide glasses J.L Prat, F. Terki *, J. Pelous Laboratoire des Verres, UMR 5587, Universit e Montpellier II Place Eug ene Bataillon, case 069, 34095 Montpellier cedex, France
Abstract Raman spectra have been investigated in the 3±1500 cmÿ1 range in two sodium oxide phosphosilicate glasses with diering ®ctive temperatures, Tf . The temperature dependence of the spectra has been measured from lower temperatures to the glass transition temperature, Tg . Up to Tg the Bose-factor rescaled spectra coincide, but a dynamical quasielastic contribution depending on Tf , was observed in a large range of temperature. Relaxational processes related to a structural reordering are observed near Tg . A connection between Tf and medium range order deduced from inelastic light scattering in this frequency range is emphasized. This study point out that the quasielastic scattered intensity originates from thermally activated structural entities related to the disorder. Ó 1998 Elsevier Science B.V. All rights reserved. PACS: 78.35.+c; 78.30.-j; 78.30.Ly
1. Introduction
2. Sample preparation and experimental set up
The eect of quenching on the low frequency dynamics of glasses have stimulated a widespread interest and a lengthening list of experiments [1± 5]. In the present paper, we consider the cooling rate aect on the dynamics of glasses both below and above the glass transition temperature, Tg . Therefore the temperature dependence of the Raman spectra has been measured from low temperature up to Tg . This work coupled both Raman and Brillouin investigations from 10 GHz to 45 THz for two glasses stabilized in the temperature transition range at two dierent temperatures. The question we pose is how do relaxational processes relate to medium range order?
Two phosphosilicate specimens of molar composition Na2 O : 2Si O2 : 3:2P2 O5 were synthetised. They were stabilized at two dierent temperatures: 400°C and 600°C in the glass transition temperature range, and quickly cooled. They have two ®ctive temperatures, Tf . In the following the samples with a Tf of about 400°C and 600°C are labelled PHOS400 and PHOS600, respectively. Further details on the chemical preparation condition are discussed elsewhere [6]. In both Brillouin and Raman experiments the samples were illuminated with a single mode ion laser at k 514.5 nm (Spectra 2020) and a power intensity near 200 mW for low temperature investigations and 1W for high temperature ones. Brillouin scattering measurements were performed by a tandem six-pass Fabry±Perot spectrometer [7]. The details of the spectrometer conditions are
* Corresponding author. Tel.: +33 4 6714 4780; fax: +33 4 6714 3498; e-mail: [email protected].
0022-3093/98/$19.00 Ó 1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 0 9 3 ( 9 8 ) 0 0 6 5 4 - 1
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
described elsewhere [8]. The position and the linewidth of the Brillouin bands were obtained by a ®t using a convolution of the apparatus function (elastic line) with a theoretical shape derived from hypersonic velocity measurements. Besides, the half Brillouin linewidth, C, is related to the spatial acoustic attenuation, `ÿ1 (`ÿ1 4pC/V). Stokes and anti-Stokes Raman spectra were measured on a conventional triple-pass grating spectrometer (Coderg T800) with a resolution of about 1 cmÿ1 (1 cmÿ1 30 GHz). Moreover, for analyzing the very low-frequency Raman scattering we have applied a double-grating single-pass monochromator (SOPRA DMSP) [9]. This experimental device is
389
especially designed for higher resolution and lower frequency light scattering studies. It covers the frequency range between the Fabry±Perot experiment and the conventional Raman spectrometer with a resolution of about 6 GHz. 3. Results The aect of the ®ctive temperature in the very frequency range 0.4±6 cmÿ1 using Brillouin and Raman scattering measurements is shown in Fig. 1. An example of very low-frequency Raman spectra obtained for sample PHOS600 at three
Fig. 1. Brillouin and low-frequency Raman scattering measurements. (a) Example of very low-frequency Raman spectra in the PHOS600 using the SOPRA DMSP2000 spectrometer. (b) Raman reduced intensity for PHOS600 vs. temperature for several frequencies near the elastic line. (c) Longitudinal attenuation measured in PHOS400 and PHOS600 vs. temperature. The errors bars correspond to the accuracy of the experimental data for the attenuation (5%). (d) Raman scattering intensity at 2 cmÿ1 vs. temperature for the two phosphosilicate glasses. For comparison, the insert presents the hypersonic attenuation temperature variations for PHOS600. For clarity, we decide to report the errors bars only on Fig. 1(c) since the accuracy of the inelastic intensity is the same (5%).
390
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
temperatures is presented (Fig. 1(a)). From these measurements we deduce the quasielastic temperature dependence, Iqe (T), for several frequencies near the elastic line (Fig. 1(b)). Note that the intensity of Iqe (T) increases with the frequency in agreement with the expected increase of the atten-
uation at high frequency. The comparison with the temperature dependence of attenuation (insert of Fig. 1(d)) is in better accordance if we consider the extracted Iqe at the lowest frequency. Indeed the observed plateau in the C T dependence is also marked in Iqe (T) at 2 cmÿ1 and begins to dis-
Fig. 2. In¯uence of the ®ctive temperature on the Raman scattering temperature dependence for temperature sets below, near and above the glass transition temperature. Below the glass temperature transition: (a) T 150 K; (b) T 300 K and (c) T 630 K. Near and above the glass transition of the PHOS400 glass (Tg 673 K): (d) T 677 K, (e) T 777 K and (f) T 800 K. Near and above the glass transition of the PHOS600 glass (Tg 833 K): (g) T 835 K, (h) T 930 K and (i) T 980 K. Thick and thin solid lines represent reduced Raman scattering intensity of the PHOS400 and PHOS600, respectively.
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
appear at higher frequencies. The results presented in Fig. 1(c) indicate that, at the lower temperature, no ®ctive temperature eect on the scattered intensity is observed while for temperature greater than 300 K a Tf eect is detected. So, we conclude that thermal activation produces ®ctive temperature dierences. Moreover Fig. 1(d) shows a qualitative agreement between the Iqe (T) and C T dependence. Fig. 2 illustrates the aect of Tf on the Raman scattering temperature dependence for a set of temperatures, less than, within the glass transition temperature and greater than Tg . Dierences are noted in the glass transition temperature range of the two samples whereas at temperatures less than and greater than Tg the spectra are superimposed. So, at lower temperatures sample properties are not modi®ed by the temperature at which they have been stabilized. Moreover, the heat annealing memory is lost at temperatures greater than Tg . Note that in the equilibrium frozen liquid, a band at 160 cmÿ1 is observed in the two samples underlying a structural reordering such as a crystallization process. 4. Discussion The temperature dependence of the quasielastic intensity, Iqe (T), at frequencies near those used in the Brillouin measurements are indicative of an analogy with that of the acoustical attenuation, C T . Therefore, the predicted hypothesis [10,11] of a common physical origin of the phonon attenuation and the light scattered intensity within a temperature range across the glass temperature transition is detected from 300 K to 1000 K as found in other glasses [12,13]. The intensity of the relaxational modes are increased by increasing the quenching temperature. Nevertheless, at T 6 150 K the dierences are less and completely disappear at 20 K. Besides, we found that at T < 300 K the correlation between C T and Iqe (T) disappears which may be due to dierent activated processes for these two properties. In fact, this observed eect could be explained by the presence of defects dierently coupled to the disorder. Some of them contribute to the acoustical attenu-
391
ation and do not interact with the photons while other local entities actively scatter the light without aect on the acoustic modes. This idea has already been suggested in a recent work in lowtemperature studies [14,15]. Moreover, interesting features are revealed by quasielastic intensity frequency dependence in the glass transition temperature intervals. It is accepted that elastic intensity point out structural reordering since the viscosity eects start near Tg . Otherwise, this study at various step in the glass transition temperature range emphasizes that Raman scattering detects structural reordering at the nanometer scale. 5. Conclusion This study reveals several important points which could be summarized as following. The ®ctive temperature aects the acoustic attenuation and is related to the aect on the quasielastic intensity within a temperature range across the glass transition. However, at temperatures, 6 150 K the aect of the ®ctive temperature on both the acoustic attenuation and the low-frequency Raman intensity disappears. This disappearance leads to the existence of relaxational processes connected with acoustic modes as suggested for the explanation of the origin of the acoustical attenuation [16]. In the samples at high temperature an increase of relaxational defects are observed. These thermally activated processes disappear at lowtemperatures. Consequently at low-temperature the quasielastic intensity decreases whatever the ®ctive temperature. On another hand, we emphasize that inelastic scattering is aected by structural modi®cations occurring at temperatures in the glass transition range. References [1] R. Vacher, M. Delsanti, J. Pelous, L. Cecchi, A. Winter, J. Zarzycky, J. Mater. Sci. 9 (1974) 829. [2] V.K. Malinovsky, V.N. Novikov, A.P. Sokolov, Phys. Lett. A 70 (1987) 19. [3] L. Borjesson, A.K. Hassan, J. Swenson, L.M. Torell, A. Fontana, Phys. Rev. Lett. 70 (1993) 1275.
392
J.L. Prat et al. / Journal of Non-Crystalline Solids 235±237 (1998) 388±392
[4] M. Kr uger, M. Solwisch, I. Petscherizin, D. Quitmann, J. Chem. Phys. 96 (1992) 7352. [5] S.L. Isakov, S.N. Ishmaev, V.K. Malinovsky, V.N. Novikov, P.P. Parshing, S.N. Popov, A.P. Sokolov, M.G. Zemlyanov, Physica A 201 (1993) 386. [6] J.L. Prat, PhD thesis, Montpellier University, 1996. [7] R. Vacher, J. Pelous, Phys. Rev. B 14 (1976) 823. [8] F. Terki, C. Levelut, M. Boissier, J. Pelous, Phys. Rev. B 53 (1996) 2411. [9] V. Mazzacurati, P. Besnassi, G. Ruocco, J. Phys. E 21 (1988) 798. [10] J. Jackle, Amorphous solids, in: W.A. Phillips (Ed.), LowTemperature Properties, Topics in Current Physics, vol. 24, Springer, Berlin.
[11] V.L. Gurevich, D. Parshin, J. Pelous, H.R. Schober, Phys. Rev. B 48 (1993) 16318. [12] C. Levelut, N. Gaimes, F. Terki, G. Cohen-Solal, J. Pelous, R. Vacher, Phys. Rev. B 51 (1995) 8606. [13] F. Terki, C. Levelut, J-L. Prat, M. Boissier, J. Pelous, J. Phys.: Condens. Matter. 8 (1996) 941. [14] J.L. Prat, F. Terki, J. Pelous, Phys. Rev. Lett. 7 (1996) 755. [15] F. Terki, J.L. Prat, J. Pelous, Philos. Mag. B 77 (2) (1998) 373. [16] D. Tielb urger, K. Merz, R. Ehrenfeld, S. Hunklinger, Phys. Rev. B 45 (1992) 2750.