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Structural study of quasicrystallization in Zr–NM (NM=Pd or Pt) metallic glasses
Journal of Non-Crystalline Solids 312–314 (2002) 594–598 www.elsevier.com/locate/jnoncrysol
Structural study of quasicrystallization in Zr–NM (NM ¼ Pd or Pt) metallic glasses Makoto Kitada a
a,1
, Muneyuki Imafuku
a,*
, Junji Saida a, Akihisa Inoue
b
Inoue Superliquid Glass Project, ERATO, Japan Science and Technology Corporation (JST), Sendai 982-0807, Japan b Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Abstract Glassy Zr70 Pd30 and Zr80 Pt20 alloys were prepared by melt spinning. Icosahedral-like local atomic configurations were identified in these alloys by ordinary and anomalous X-ray scattering measurements. In the case of Zr70 Pd30 alloy, the total coordination numbers (N) around Zr and Pd in the nearest neighboring region were 11.3 and 8.9, respectively, which implies the existence of an icosahedral-like local atomic structure around Zr. On the other hand, the glassy Zr80 Pt20 alloy shows a pronounced pre-peak in its X-ray scattering intensity profile, indicating strong chemical short-range-ordered clusters. The N values around Zr and Pt are both 11.1, and close to 12.0. Furthermore, the atomic distances of Zr–Zr and Pt–Pt are almost the same. Thus, icosahedral-like local atomic structures with strong correlations are already formed both around Zr and Pt. The stronger chemical affinity of the Zr–Pt pair over the Zr–Pd pair seems to contribute to the stabilization of the quasicrystalline phase through the rigid icosahedral clusters. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 61.10.Eq; 61.44.Br; 81.05.Kf
1. Introduction The formation of an icosahedral quasicrystalline phase (i-phase) has been found in the primary crystallization stage of various Zr-based glassy
*
Corresponding author. Present address: Advanced Technology Research Laboratories, Nippon Steel Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511, Japan. Tel.: +81-439 80 2237; fax: +81-439 80 2746. E-mail address: [email protected] (M. Imafuku). 1 Present address: Fuji Photo Film Co., Ltd., Karagawa 2588538, Japan.
alloys containing noble metal (NM) elements in Zr–Al–Ni–Cu [1], Zr–Al–Ni [2] and Zr–Ni [3] base alloys. In these alloys, a complex combination of atomic pairs with large negative heats of mixing (Zr–NM and Zr–Ni) and nearly zero or positive heats of mixing (NM–Ni) has been thought to contribute to the formation of the i-phase through the inhibition of the precipitation of a crystalline phase. Recently, the formation of the i-phase was also found in a binary Zr70 Pd30 glassy alloy [4]. Similarly, the Zr–Pt glassy alloy is expected to transform into the i-phase from an analogy with the Zr–Pd system. However, it is difficult to obtain a glassy phase, and the i-phase has been reported
0022-3093/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 0 9 3 ( 0 2 ) 0 1 7 9 1 - X
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to form in an as-quenched state for a Zr80 Pt20 alloy [5]. More recently, a glassy single phase was obtained in an as-quenched Zr80 Pt20 alloy prepared at a high roller speed of 50 m/s [6]. It has been suggested that the strong chemical affinity among the constituents in these alloys causes to the stabilization of an icosahedral short-range-ordered structure. However, precise information about this is unclear up to now. In this paper, the shortrange-ordered structures in the glassy Zr70 Pd30 and Zr80 Pt20 alloys are compared in conjunction with the quasicrystallization process of these alloys.
2. Experimental Glassy alloy ribbons of Zr70 Pd30 and Zr80 Pt20 were prepared by the single-roller melt spinning technique from arc melted master ingots in an Ar atmosphere. The roller surface speeds were 30 m/s for Zr70 Pd30 and 50 m/s for Zr80 Pt20 , respectively. The faster roller speed was required to obtain a glassy phase for the Zr80 Pt20 alloy. The phase transformation behavior was measured by DSC at a heating rate of 0.67 K/s. The anomalous X-ray scattering (AXS) measurements were made at the beam line BL-7C in the Photon Factory of the National Laboratory for High Energy Accelerator Research Organization, Tsukuba, Japan. In the AXS measurements, energy differential intensities were observed at 50 and 300 eV below the Zr–K absorption edge. The observed AXS intensities were corrected and converted to electron units per atom. The environmental radial distribution function (RDF) around Zr was evaluated by the Fourier transformation of the energy differential interference functions. The ordinary X-ray scattering measurement was performed with MoKa radiation produced by a rotating anode X-ray generator and was analyzed in a similar way.
3. Results Fig. 1 shows DSC curves for the glassy Zr70 Pd30 and Zr80 Pt20 alloys. Two distinct exothermic peaks
Fig. 1. DSC curves of the glassy Zr70 Pd30 and Zr80 Pt20 alloys. The heating rate is 0.67 K/s.
are observed. They correspond to quasicrystallization and crystallization reactions [4,6]. Although the crystallization temperature is much higher for the Zr80 Pt20 alloy, the onset temperatures of the quasicrystallization in these alloys are almost the same, near 715 K. The exothermic heats in these reactions are significantly different, 24.0 J/g for Zr70 Pd30 and 3.5 J/g for Zr80 Pt20 . This indicates that the free energy difference, DG, for the quasicrystallization reaction is much smaller for the glassy Zr80 Pt20 alloy than that for the Zr70 Pd30 one. The X-ray intensity profiles of the Zr80 Pt20 and Zr70 Pd30 glassy alloys are compared in Fig. 2. A pronounced pre-peak is observed at 16.9 nm1 only in the glassy Zr80 Pt20 alloy. This feature indicates the existence of a strong chemical short-rangeordered structure in the glassy alloy [7], which may become the nuclei for the quasicrystalline phase with annealing [8]. More detailed information about the local atomic structures was obtained from the RDF.
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Fig. 2. X-ray scattering intensity profiles for the glassy Zr70 Pd30 and Zr80 Pt20 alloys.
The ordinary interference functions, QiðQÞ, and the energy differential interference functions for Zr, QDiZr ðQÞ, in the glassy Zr70 Pd30 alloy are shown in Fig. 3. The non-linear least-squares variation method [9,10] was used to fit the interference functions. The solid and dotted curves in this figure correspond to the experimental and calculated functions. Similarly, the ordinary interference function, QiðQÞ in the glassy Zr80 Pt20 alloy is shown in Fig. 4. The calculated curves agree with the experimental results by considering the first nearest neighboring shell for these alloys as shown in Figs. 3 and 4. The ordinary (solid curves) and environmental (dotted curves) RDFs were calculated from the Fourier transformation of the ordinary and energy differential interference functions. Here, the environmental RDF means the RDF around Zr. The data of these alloys are summarized in Fig. 5. The fit positions of the Zr– Zr, Zr–Pd, Pd–Pd, Zr–Pt and Pt–Pt pairs are also indicated in this figure.
Fig. 3. Ordinary and energy differential interference functions for the glassy Zr70 Pd30 alloy. The solid and dotted curves correspond to the experimental and calculated ones, respectively.
Fig. 4. Ordinary interference function of the glassy Zr80 Pt20 alloy. The solid and dotted curves correspond to the experimental and calculated ones, respectively.
4. Discussion The calculated nearest neighbor atomic distances and coordination numbers for the glassy
M. Kitada et al. / Journal of Non-Crystalline Solids 312–314 (2002) 594–598
Fig. 5. Environmental (dotted) and total (solid) RDFs for the glassy Zr70 Pd30 and Zr80 Pt20 alloys. The arrows indicate the positions of Zr–Zr, Zr–Pd, Pd–Pd, Zr–Pt and Pt–Pt pairs.
Zr70 Pd30 and Zr80 Pt20 alloys are compared in Table 1. In the case of the glassy Zr70 Pd30 alloy, the local atomic structure around Zr can be regarded as an icosahedral-like structure because the sum of the coordination numbers around Zr is 11.3, and hence very close to 12.0. On the other hand, the total coordination numbers around Pd are 8.9. These results imply that the icosahedral local structure is formed around the Zr atoms rather
597
than the Pd atoms. However, the icosahedral-like structure should be distorted to some extent because of the difference in the atomic radii of Zr and Pd. In the case of the glassy Zr80 Pt20 alloy, the total coordination numbers around Pt and Zr are both 11.1, and hence close to 12.0. It is also seen that the atomic distance of the Pt–Pt pair (0.326 nm) is longer than the value expected from its atomic radius (about 0.278 nm) and almost the same as the observed value for the Zr–Zr pair. Considering the appearance of the pre-peak in the X-ray scattering profile as described above, the icosahedral-like local atomic clusters might be already formed both around Zr and Pt, with strong correlations even in the glassy phase. Similar local structures around Zr and Pt have been found in the Zr2 Ni big-cube phase, proposed as a related structure to i-phase [11]. The stronger chemical affinity of the Zr–Pt atomic pair (DHmix ¼ 100 kJ/mol) over that of the Zr–Pd pair (DHmix ¼ 91 kJ/mol) probably contributes to the stabilization of the quasicrystalline phase through the formation of this kind of rigid icosahedral clusters. This is the reason for the difficulty in forming the glassy phase rather than an i-phase in the as-quenched state.
5. Conclusions The difference in the local atomic structures of the glassy Zr70 Pd30 and Zr80 Pt20 alloys has been characterized. A pronounced pre-peak, which is an evidence of the strong chemical short-rangeordering cluster, was found in the X-ray scattering intensity profile of the Zr80 Pt20 glassy alloy. Icosahedral-like local atomic structures were recognized
Table 1 Coordination numbers (N) and interatomic distances (r) for the glassy Zr70 Pd30 and Zr80 Pt20 alloys Pairs Zr–Zr Zr–Pd or Zr–Pt (Pd–Zr or Pt–Zr) Pd–Pd or Pt–Pt
Zr70 Pd30
Zr80 Pt20
r (nm)
N (atoms)
r (nm)
N (atoms)
0.326 0.002 0.289 0.001
8.3 0.3 3.0 0.2 (7.0 0.2) 1.9 0.2
0.326 0.002 0.286 0.001
8.8 0.3 2.3 0.2 (9.3 0.2) 1.8 0.2
0.273 0.002
0.326 0.002
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around both Zr and Pt in the glassy Zr80 Pt20 alloy, whereas this kind of local structure formed only around Zr in the glassy Zr70 Pd30 alloy. In the present alloys, the existence of the icosahedral-like local atomic structure is an important factor in the formation of the i-phase. The difference in the nature of these kinds of clusters might originate from the stronger chemical affinity of the Zr–Pt pair over the Zr–Pd pair, leading to the stabilization of the quasicrystalline phase in the Zr80 Pt20 alloy.
References [1] M.W. Chen, T. Zhang, A. Inoue, A. Sakai, T. Sakurai, Appl. Phys. Lett. 75 (1999) 1697.
[2] A. Inoue, J. Saida, M. Matsushita, T. Sakurai, Mater. Trans. JIM 41 (2000) 362. [3] J. Saida, M. Matsushita, A. Inoue, Mater. Trans. JIM 41 (2000) 543. [4] J. Saida, M. Matsushita, C. Li, A. Inoue, Philos. Mag. Lett. 81 (2001) 39. [5] J. Saida, M. Matsushita, A. Inoue, Appl. Phys. Lett. 77 (2000) 73. [6] J. Saida, M. Matsushita, A. Inoue, Mater. Trans. 42 (2001) 1103. [7] H.S. Chen, D. Koskenmaki, C.H. Chen, Phys. Rev. B 35 (1987) 3715. [8] E. Matsubara, Y. Waseda, A.P. Tsai, A. Inoue, T. Masumoto, J. Mater. Sci. 25 (1990) 2507. [9] A.H. Narten, H.A. Levy, Science 165 (1965) 447. [10] A.H. Narten, J. Chem. Phys. 56 (1972) 1905. [11] E. Matsubara, T. Nakamura, M. Sakurai, M. Imafuku, S. Sato, J. Saida, A. Inoue, in: Mater. Res. Symp. Proc., vol. 644, 2001, p. L1.1.1.
Structural study of quasicrystallization in Zr–NM (NM ¼ Pd or Pt) metallic glasses Makoto Kitada a
a,1
, Muneyuki Imafuku
a,*
, Junji Saida a, Akihisa Inoue
b
Inoue Superliquid Glass Project, ERATO, Japan Science and Technology Corporation (JST), Sendai 982-0807, Japan b Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Abstract Glassy Zr70 Pd30 and Zr80 Pt20 alloys were prepared by melt spinning. Icosahedral-like local atomic configurations were identified in these alloys by ordinary and anomalous X-ray scattering measurements. In the case of Zr70 Pd30 alloy, the total coordination numbers (N) around Zr and Pd in the nearest neighboring region were 11.3 and 8.9, respectively, which implies the existence of an icosahedral-like local atomic structure around Zr. On the other hand, the glassy Zr80 Pt20 alloy shows a pronounced pre-peak in its X-ray scattering intensity profile, indicating strong chemical short-range-ordered clusters. The N values around Zr and Pt are both 11.1, and close to 12.0. Furthermore, the atomic distances of Zr–Zr and Pt–Pt are almost the same. Thus, icosahedral-like local atomic structures with strong correlations are already formed both around Zr and Pt. The stronger chemical affinity of the Zr–Pt pair over the Zr–Pd pair seems to contribute to the stabilization of the quasicrystalline phase through the rigid icosahedral clusters. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 61.10.Eq; 61.44.Br; 81.05.Kf
1. Introduction The formation of an icosahedral quasicrystalline phase (i-phase) has been found in the primary crystallization stage of various Zr-based glassy
*
Corresponding author. Present address: Advanced Technology Research Laboratories, Nippon Steel Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511, Japan. Tel.: +81-439 80 2237; fax: +81-439 80 2746. E-mail address: [email protected] (M. Imafuku). 1 Present address: Fuji Photo Film Co., Ltd., Karagawa 2588538, Japan.
alloys containing noble metal (NM) elements in Zr–Al–Ni–Cu [1], Zr–Al–Ni [2] and Zr–Ni [3] base alloys. In these alloys, a complex combination of atomic pairs with large negative heats of mixing (Zr–NM and Zr–Ni) and nearly zero or positive heats of mixing (NM–Ni) has been thought to contribute to the formation of the i-phase through the inhibition of the precipitation of a crystalline phase. Recently, the formation of the i-phase was also found in a binary Zr70 Pd30 glassy alloy [4]. Similarly, the Zr–Pt glassy alloy is expected to transform into the i-phase from an analogy with the Zr–Pd system. However, it is difficult to obtain a glassy phase, and the i-phase has been reported
0022-3093/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 0 9 3 ( 0 2 ) 0 1 7 9 1 - X
M. Kitada et al. / Journal of Non-Crystalline Solids 312–314 (2002) 594–598
595
to form in an as-quenched state for a Zr80 Pt20 alloy [5]. More recently, a glassy single phase was obtained in an as-quenched Zr80 Pt20 alloy prepared at a high roller speed of 50 m/s [6]. It has been suggested that the strong chemical affinity among the constituents in these alloys causes to the stabilization of an icosahedral short-range-ordered structure. However, precise information about this is unclear up to now. In this paper, the shortrange-ordered structures in the glassy Zr70 Pd30 and Zr80 Pt20 alloys are compared in conjunction with the quasicrystallization process of these alloys.
2. Experimental Glassy alloy ribbons of Zr70 Pd30 and Zr80 Pt20 were prepared by the single-roller melt spinning technique from arc melted master ingots in an Ar atmosphere. The roller surface speeds were 30 m/s for Zr70 Pd30 and 50 m/s for Zr80 Pt20 , respectively. The faster roller speed was required to obtain a glassy phase for the Zr80 Pt20 alloy. The phase transformation behavior was measured by DSC at a heating rate of 0.67 K/s. The anomalous X-ray scattering (AXS) measurements were made at the beam line BL-7C in the Photon Factory of the National Laboratory for High Energy Accelerator Research Organization, Tsukuba, Japan. In the AXS measurements, energy differential intensities were observed at 50 and 300 eV below the Zr–K absorption edge. The observed AXS intensities were corrected and converted to electron units per atom. The environmental radial distribution function (RDF) around Zr was evaluated by the Fourier transformation of the energy differential interference functions. The ordinary X-ray scattering measurement was performed with MoKa radiation produced by a rotating anode X-ray generator and was analyzed in a similar way.
3. Results Fig. 1 shows DSC curves for the glassy Zr70 Pd30 and Zr80 Pt20 alloys. Two distinct exothermic peaks
Fig. 1. DSC curves of the glassy Zr70 Pd30 and Zr80 Pt20 alloys. The heating rate is 0.67 K/s.
are observed. They correspond to quasicrystallization and crystallization reactions [4,6]. Although the crystallization temperature is much higher for the Zr80 Pt20 alloy, the onset temperatures of the quasicrystallization in these alloys are almost the same, near 715 K. The exothermic heats in these reactions are significantly different, 24.0 J/g for Zr70 Pd30 and 3.5 J/g for Zr80 Pt20 . This indicates that the free energy difference, DG, for the quasicrystallization reaction is much smaller for the glassy Zr80 Pt20 alloy than that for the Zr70 Pd30 one. The X-ray intensity profiles of the Zr80 Pt20 and Zr70 Pd30 glassy alloys are compared in Fig. 2. A pronounced pre-peak is observed at 16.9 nm1 only in the glassy Zr80 Pt20 alloy. This feature indicates the existence of a strong chemical short-rangeordered structure in the glassy alloy [7], which may become the nuclei for the quasicrystalline phase with annealing [8]. More detailed information about the local atomic structures was obtained from the RDF.
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M. Kitada et al. / Journal of Non-Crystalline Solids 312–314 (2002) 594–598
Fig. 2. X-ray scattering intensity profiles for the glassy Zr70 Pd30 and Zr80 Pt20 alloys.
The ordinary interference functions, QiðQÞ, and the energy differential interference functions for Zr, QDiZr ðQÞ, in the glassy Zr70 Pd30 alloy are shown in Fig. 3. The non-linear least-squares variation method [9,10] was used to fit the interference functions. The solid and dotted curves in this figure correspond to the experimental and calculated functions. Similarly, the ordinary interference function, QiðQÞ in the glassy Zr80 Pt20 alloy is shown in Fig. 4. The calculated curves agree with the experimental results by considering the first nearest neighboring shell for these alloys as shown in Figs. 3 and 4. The ordinary (solid curves) and environmental (dotted curves) RDFs were calculated from the Fourier transformation of the ordinary and energy differential interference functions. Here, the environmental RDF means the RDF around Zr. The data of these alloys are summarized in Fig. 5. The fit positions of the Zr– Zr, Zr–Pd, Pd–Pd, Zr–Pt and Pt–Pt pairs are also indicated in this figure.
Fig. 3. Ordinary and energy differential interference functions for the glassy Zr70 Pd30 alloy. The solid and dotted curves correspond to the experimental and calculated ones, respectively.
Fig. 4. Ordinary interference function of the glassy Zr80 Pt20 alloy. The solid and dotted curves correspond to the experimental and calculated ones, respectively.
4. Discussion The calculated nearest neighbor atomic distances and coordination numbers for the glassy
M. Kitada et al. / Journal of Non-Crystalline Solids 312–314 (2002) 594–598
Fig. 5. Environmental (dotted) and total (solid) RDFs for the glassy Zr70 Pd30 and Zr80 Pt20 alloys. The arrows indicate the positions of Zr–Zr, Zr–Pd, Pd–Pd, Zr–Pt and Pt–Pt pairs.
Zr70 Pd30 and Zr80 Pt20 alloys are compared in Table 1. In the case of the glassy Zr70 Pd30 alloy, the local atomic structure around Zr can be regarded as an icosahedral-like structure because the sum of the coordination numbers around Zr is 11.3, and hence very close to 12.0. On the other hand, the total coordination numbers around Pd are 8.9. These results imply that the icosahedral local structure is formed around the Zr atoms rather
597
than the Pd atoms. However, the icosahedral-like structure should be distorted to some extent because of the difference in the atomic radii of Zr and Pd. In the case of the glassy Zr80 Pt20 alloy, the total coordination numbers around Pt and Zr are both 11.1, and hence close to 12.0. It is also seen that the atomic distance of the Pt–Pt pair (0.326 nm) is longer than the value expected from its atomic radius (about 0.278 nm) and almost the same as the observed value for the Zr–Zr pair. Considering the appearance of the pre-peak in the X-ray scattering profile as described above, the icosahedral-like local atomic clusters might be already formed both around Zr and Pt, with strong correlations even in the glassy phase. Similar local structures around Zr and Pt have been found in the Zr2 Ni big-cube phase, proposed as a related structure to i-phase [11]. The stronger chemical affinity of the Zr–Pt atomic pair (DHmix ¼ 100 kJ/mol) over that of the Zr–Pd pair (DHmix ¼ 91 kJ/mol) probably contributes to the stabilization of the quasicrystalline phase through the formation of this kind of rigid icosahedral clusters. This is the reason for the difficulty in forming the glassy phase rather than an i-phase in the as-quenched state.
5. Conclusions The difference in the local atomic structures of the glassy Zr70 Pd30 and Zr80 Pt20 alloys has been characterized. A pronounced pre-peak, which is an evidence of the strong chemical short-rangeordering cluster, was found in the X-ray scattering intensity profile of the Zr80 Pt20 glassy alloy. Icosahedral-like local atomic structures were recognized
Table 1 Coordination numbers (N) and interatomic distances (r) for the glassy Zr70 Pd30 and Zr80 Pt20 alloys Pairs Zr–Zr Zr–Pd or Zr–Pt (Pd–Zr or Pt–Zr) Pd–Pd or Pt–Pt
Zr70 Pd30
Zr80 Pt20
r (nm)
N (atoms)
r (nm)
N (atoms)
0.326 0.002 0.289 0.001
8.3 0.3 3.0 0.2 (7.0 0.2) 1.9 0.2
0.326 0.002 0.286 0.001
8.8 0.3 2.3 0.2 (9.3 0.2) 1.8 0.2
0.273 0.002
0.326 0.002
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M. Kitada et al. / Journal of Non-Crystalline Solids 312–314 (2002) 594–598
around both Zr and Pt in the glassy Zr80 Pt20 alloy, whereas this kind of local structure formed only around Zr in the glassy Zr70 Pd30 alloy. In the present alloys, the existence of the icosahedral-like local atomic structure is an important factor in the formation of the i-phase. The difference in the nature of these kinds of clusters might originate from the stronger chemical affinity of the Zr–Pt pair over the Zr–Pd pair, leading to the stabilization of the quasicrystalline phase in the Zr80 Pt20 alloy.
References [1] M.W. Chen, T. Zhang, A. Inoue, A. Sakai, T. Sakurai, Appl. Phys. Lett. 75 (1999) 1697.
[2] A. Inoue, J. Saida, M. Matsushita, T. Sakurai, Mater. Trans. JIM 41 (2000) 362. [3] J. Saida, M. Matsushita, A. Inoue, Mater. Trans. JIM 41 (2000) 543. [4] J. Saida, M. Matsushita, C. Li, A. Inoue, Philos. Mag. Lett. 81 (2001) 39. [5] J. Saida, M. Matsushita, A. Inoue, Appl. Phys. Lett. 77 (2000) 73. [6] J. Saida, M. Matsushita, A. Inoue, Mater. Trans. 42 (2001) 1103. [7] H.S. Chen, D. Koskenmaki, C.H. Chen, Phys. Rev. B 35 (1987) 3715. [8] E. Matsubara, Y. Waseda, A.P. Tsai, A. Inoue, T. Masumoto, J. Mater. Sci. 25 (1990) 2507. [9] A.H. Narten, H.A. Levy, Science 165 (1965) 447. [10] A.H. Narten, J. Chem. Phys. 56 (1972) 1905. [11] E. Matsubara, T. Nakamura, M. Sakurai, M. Imafuku, S. Sato, J. Saida, A. Inoue, in: Mater. Res. Symp. Proc., vol. 644, 2001, p. L1.1.1.