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Electronic structure and local environment of non-transition elements in ternary metallic glasses
Materials Science and Engineering, 99 (1988) 269-271
269
Electronic Structure and Local Environment of Non-transition Elements in Ternary Metallic Glasses* K. TANAKA, N. SHIBAGAKI and T. YAMAUCHI Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa, Nagoya 466 (Japan)
Abstract
Valence electronic structures of ternary alloy glasses of late transition metal-early transition metal-nontransition metal ( L T M - E T M - M ) systems have been studied by means of soft X-ray emission spectroscopy and photoelectron spectroscopy. The samples investigated have the compositions (L TM33ETM67)soA120 and others, where L T M = Fe, Co, Ni, Cuor Pd, E T M =- Ti or Zr and M - Al or Si. The soft X-ray emission Al Kfl spectrum manifests doublet peaks attributable to A l L T M and A I - E T M atomic bonding, while the Si Kfl spectrum causes a single peak due to Si ETM bonding. These .features suggest that the local environments about aluminium and silicon are not necessarily similar in these ternary alloy glasses. 1. Introduction
The structure and electronic properties of metalmetalloid alloy glasses have been studied widely, and short-range atomic configurations as well as the nature of interatomic bonding between metals and metalloids have been made clear for certain binary alloy glasses [ 1]. These include 3d or 4<1 late transition metals (LTM ~ Fe, Co, Ni, Cu or Pd) and metalloids (M - B, Al, Si or P). In ternary alloy glasses consisting only of the late transition metals and metalloids, the structural and bonding characteristics of the binary systems might almost remain. However, when early transition metals (ETM - Ti or Zr) are added to form ternary L T M - E T M - M alloy glasses, these characteristics may be altered significantly because the early transition metals tend to react strongly with the late transition metals and metalloids and thereby to build up new atomic and electronic configurations around them. This type of problem has not yet been fully investigated. The objective of the present work is to provide soft X-ray emission spectra of the valence bands of certain
*Paper presented at the Sixth International Conference on Rapidly Quenched Metals, Montr6al, August 3 7, 1987. 0025-5416/88/$3.50
L T M - E T M - M (M = AI or Si) alloy glasses and to reveal the electronic structures and local environments about the metalloid atoms in these ternary glasses. X-ray photoelectron spectra were also measured for comparison. 2. Experimental procedure
Several types of ribbon sample with the compositions (LTM33ETM67)8oM20 and others were prepared by liquid quenching, X-ray diffraction measurements revealed that all the samples had glassy structures. Their chemical compositions were checked by X-ray microanalyses. Since the analysed values were close to the nominal values, the latter were used to designate each sample. They were mechanically polished and subjected to soft X-ray emission spectroscopy measurements. The procedure for the measurements and the data processing were similar to those described elsewhere [2-5]. 3. Results and discussion
Soft
X-ray
AI Kfl
emission
spectra
of
(LTM33Zr67)8oAIzo,where LTM = Fe, Co, Ni or Cu, are shown in Fig. 1. These spectra project the partial density of states of AI 3p bands in the glassy alloys. The photon energies are scaled relative to the Fermi levels EF. As can be clearly seen in the deconvoluted spectra (broken curves), all the spectra except that for iron can be decomposed into two peaks, one at - 1.8 eV (cobalt, nickel and copper) and another at - 2 . 6 eV (cobalt), - 2.9 eV (nickel) or - 4 . 3 eV (copper). For iron, only a single peak is seen at - 2.6 eV. The higher energy (lower binding energy) peaks of the doublets which are commonly seen for cobalt, nickel and copper are interpreted to reflect A1 3p-Zr 4d bonding (hybridization); their energies are somewhat shallower, however, than the energy of - 2.4 eV for a Zr3A1 crystal (not shown in the figure). In contrast, the lower energy (higher binding energy) peaks of the doublets, together with that for iron, are interpreted as arising from A1 3p-LTM 3d bonding; their peak © Elsevier Sequoia/Printed in The Netherlands
270
r-1
c
c$ ^
~,
>-H t"
co z w
J
(Pd33Zr6?)80AI20
f-
z )I.--
-15
-i0
-5 0 E-E F leVI
(,o z LI_I I--Z I--,i
(Pd33Zr67)90Sho
Fig. 1. Soft X-ray AI Kfl emission spectra of (LTM33Zr67)80A120 alloy glasses, where LTM = Fe, Co, Ni or Cu: - - , the corresponding spectra after deconvolution.
~'/Zr855i15 I
positions nearly coincide with those of the corresponding LTM-AI crystalline alloys [2-4]. It is noteworthy here that the intensity of the lower energy peak relative to that of the higher energy peak is strong for iron, comparable for cobalt and nickel, and weak for copper. This may suggest that the chemical environment about aluminium atoms is not necessarily determined by a statistical distribution of late and early transition metal atoms. Rather, certain preferential atomic bonding, such as Fe-AI in Fe-Zr-AI and Zr-AI in Cu-Zr-AI systems, may be present in these ternary glasses. In Fig. 2, soft X-ray emission A1 Kfl and Si Kfl spectra of (Pd33Zr67)s0A12o and (Pd33Zr67)9oSi]0 res p e c t i v e l y are shown and compared with the X-ray photoelectron spectrum of Pd35Zr6s. This X-ray photoelectron spectrum is not modified appreciably on alloying with aluminium or silicon. The A1 K# spectrum manifests two peaks at - 2 . 0 and - 4 . 7 eV. The former is attributable to A1 3p-Zr 4d bonding as stated above, while the latter arises from A1 3p-Pd 4d bonding. This peak profile appears to be consistent with the fact that the X-ray photoelectron spectrum manifests Zr 4d- and Pd 4d-derived bands at - 0 . 5 eV and - 4 . 0 e V respectively; in a transition metalnon-transition metal system, p-d bonding states are
-15
-i0
I
-5
E-E
F
!
!
0
5
[eV]
Fig. 2. Soft X-ray emission AI Kfl spectrum of (Pd33Zr67)soA120 and Si K# spectrum of (Pd33Zr67)905ilo, compared with the Xray photoelectron spectrum of Pd35Zr65: , Si K# spectrum of Zr85Si t 5-
formed, in principle, near or below the bottom of the d band of the transition metal [2]. However, this type of two-peak structure cannot be clearly seen in the Si K# spectrum, projecting the partial density of states of the Si 3p band in the glass. It consists of a single asymmetric peak at - 4 . 3 eV. Since a similar but less asymmetric peak is observed in a ZrssSi,5 alloy glass (broken curve), this peak can be ascribed mainly to Si 3p-Zr 4d bonding. It is important to note that, in contrast with the A1-Zr bonding, the Si-Zr bonding is accompanied by a marked increase in the binding energy. The formation of Si 3pPd 4d bonding cannot be clearly recognized. The bonding peak should occur at around - 5.8 eV, since a prominent peak has been observed at this energy in Pd-Si alloy glasses [5]. It may therefore contribute, if at all, to the lower energy tail of the asymmetric spectrum. The above features may be an indication that,
271 trum manifests Ti 3d- and Cu 3d-derived bands at - 0 . 5 eV and - 3.4 eV respectively. The Si Kfl spectrum, however, presents only a single peak at - 3.9 eV. This peak is almost identical with that of a Ti83Si17 alloy glass (broken curve) and hence is attributable to Si 3p-Ti 3d bonding. A small hump is seen on the lower energy side of this peak. It may arise from Si 3p-Cu 3d bonding, because its energy nearly coincides with that of an Si Cu bonding peak ( - 5.2 eV) observed in crystalline Cu-Si alloys [2, 3]. The above result suggests that the silicon atoms in this ternary glass are preferably bound to the sites whose major neighbours are titanium atoms.
Cu30Ti70
...I-,. C
:5
4. Summary and conclusion
(Cu33Ti6?)80AI20
f,.i_...i
At K B
>-,. I-.. z w ~-z
(Cm3T7)9OSi Si KB Ti835i17 |
-15
I
-10
!
-5
!
!
0
5
E-E F r e v ' l Fig. 3. Soft X-ray emission AI Kfl spectrum of (Cu33Ti67)soA12o
and Si Kfl spectrum of (Cu33Ti67)905ilocompared with the Xray photoelectron spectrum of Cu3oTi7o: , Si Kfl spectrum of Ti83Si17.
By measuring soft X-ray emission band spectra of ternary L T M - E T M - M (M = A1 or Si) alloy glasses, the nature of chemical bonding and short-range structure about aluminium and silicon atoms in the glasses have been studied. It has been shown that, in the L T M - E T M AI glasses, the aluminium atoms are in an environment of both late and early transition metal neighbours; of the late and early transition metals investigated, aluminium appears to have the most preference for iron, intermediate for zirconium and titanium, and least for copper. In contrast, in the L T M - E T M - S i glasses, the silicon atoms are surrounded preferably by the early transition metal neighbours irrespective of the species of the late transition metals. The above trends in the chemical affinity ofaluminium and silicon for the late and early transition metals seem to have strong relevance to the formability and electronic properties of these ternary alloy glasses [6].
Acknowledgments while the aluminium atoms are surrounded by both zirconium and palladium neighbours, the silicon atoms are placed on the sites surrounded mostly by zirconium atoms. Quite a similar conclusion has been derived for Ni-Zr~(AI, Si) alloy glasses [6]. Figure 3 shows soft X-ray emission AI Kfl and Si Kfl spectra of (Cu3~Ti67)soA12o and (Cu33Ti67)9oSilo respectively, together with the X-ray photoelectron spectrum of Cu3oTi7o. The A1 Kfl spectrum consists of two peaks, one at - 1.8 eV which is related to A1 3pTi 3d bonding and the other at - 3.8 eV due to AI 31~ Cu 3d bonding. This assignment is based on the fact that an AI Ti bonding peak has been observed at - 2 . 4 eV in a Ti3A1 crystal (not shown in the figure) and, in addition, an AI-Cu bonding peak has been observed at - 5.0 eV in Cu A1 crystalline alloys [2-4]. The above spectral feature of the ternary glass is consistent with the fact that the X-ray photoelectron spec-
The authors acknowledge Professor K. Suzuki and Dr. T. Fukunaga for providing us with ribbon samples of the Ti-Si and Z ~ S i alloy glasses. They also express sincere thanks to Professor U. Mizutani and Mr. Y. Yamada for cooperation in preparing the glass samples and for valuable discussions.
References 1 F. E. Luborsky (ed.), Amorphous Metallic Alloys, Butterworths, London, 1983. 2 K. Tanaka, M. Matsumoto, S. Maruno and A. Hiraki, Appl. Phys. Lett., 27(1975) 529. 3 K. Tanaka and A. Hiraki, Jpn. J. Appl. Phys. 17, Suppl. 2 (1978) 121. 4 K. Tanaka, T. Saito and M. Yasuda, J. Phys. Soe. Jpn., 52 (1983) 1718. 5 K. Tanaka, T. Saito, K. Suzuki and R. Hasegawa, Phys. Rev. B, 32 (1985) 6853. 6 Y. Yamada, Y. Itoh., U. Mizutani, N. Shibagaki and K. Tanaka, J. Phys. F, to be published.
269
Electronic Structure and Local Environment of Non-transition Elements in Ternary Metallic Glasses* K. TANAKA, N. SHIBAGAKI and T. YAMAUCHI Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa, Nagoya 466 (Japan)
Abstract
Valence electronic structures of ternary alloy glasses of late transition metal-early transition metal-nontransition metal ( L T M - E T M - M ) systems have been studied by means of soft X-ray emission spectroscopy and photoelectron spectroscopy. The samples investigated have the compositions (L TM33ETM67)soA120 and others, where L T M = Fe, Co, Ni, Cuor Pd, E T M =- Ti or Zr and M - Al or Si. The soft X-ray emission Al Kfl spectrum manifests doublet peaks attributable to A l L T M and A I - E T M atomic bonding, while the Si Kfl spectrum causes a single peak due to Si ETM bonding. These .features suggest that the local environments about aluminium and silicon are not necessarily similar in these ternary alloy glasses. 1. Introduction
The structure and electronic properties of metalmetalloid alloy glasses have been studied widely, and short-range atomic configurations as well as the nature of interatomic bonding between metals and metalloids have been made clear for certain binary alloy glasses [ 1]. These include 3d or 4<1 late transition metals (LTM ~ Fe, Co, Ni, Cu or Pd) and metalloids (M - B, Al, Si or P). In ternary alloy glasses consisting only of the late transition metals and metalloids, the structural and bonding characteristics of the binary systems might almost remain. However, when early transition metals (ETM - Ti or Zr) are added to form ternary L T M - E T M - M alloy glasses, these characteristics may be altered significantly because the early transition metals tend to react strongly with the late transition metals and metalloids and thereby to build up new atomic and electronic configurations around them. This type of problem has not yet been fully investigated. The objective of the present work is to provide soft X-ray emission spectra of the valence bands of certain
*Paper presented at the Sixth International Conference on Rapidly Quenched Metals, Montr6al, August 3 7, 1987. 0025-5416/88/$3.50
L T M - E T M - M (M = AI or Si) alloy glasses and to reveal the electronic structures and local environments about the metalloid atoms in these ternary glasses. X-ray photoelectron spectra were also measured for comparison. 2. Experimental procedure
Several types of ribbon sample with the compositions (LTM33ETM67)8oM20 and others were prepared by liquid quenching, X-ray diffraction measurements revealed that all the samples had glassy structures. Their chemical compositions were checked by X-ray microanalyses. Since the analysed values were close to the nominal values, the latter were used to designate each sample. They were mechanically polished and subjected to soft X-ray emission spectroscopy measurements. The procedure for the measurements and the data processing were similar to those described elsewhere [2-5]. 3. Results and discussion
Soft
X-ray
AI Kfl
emission
spectra
of
(LTM33Zr67)8oAIzo,where LTM = Fe, Co, Ni or Cu, are shown in Fig. 1. These spectra project the partial density of states of AI 3p bands in the glassy alloys. The photon energies are scaled relative to the Fermi levels EF. As can be clearly seen in the deconvoluted spectra (broken curves), all the spectra except that for iron can be decomposed into two peaks, one at - 1.8 eV (cobalt, nickel and copper) and another at - 2 . 6 eV (cobalt), - 2.9 eV (nickel) or - 4 . 3 eV (copper). For iron, only a single peak is seen at - 2.6 eV. The higher energy (lower binding energy) peaks of the doublets which are commonly seen for cobalt, nickel and copper are interpreted to reflect A1 3p-Zr 4d bonding (hybridization); their energies are somewhat shallower, however, than the energy of - 2.4 eV for a Zr3A1 crystal (not shown in the figure). In contrast, the lower energy (higher binding energy) peaks of the doublets, together with that for iron, are interpreted as arising from A1 3p-LTM 3d bonding; their peak © Elsevier Sequoia/Printed in The Netherlands
270
r-1
c
c$ ^
~,
>-H t"
co z w
J
(Pd33Zr6?)80AI20
f-
z )I.--
-15
-i0
-5 0 E-E F leVI
(,o z LI_I I--Z I--,i
(Pd33Zr67)90Sho
Fig. 1. Soft X-ray AI Kfl emission spectra of (LTM33Zr67)80A120 alloy glasses, where LTM = Fe, Co, Ni or Cu: - - , the corresponding spectra after deconvolution.
~'/Zr855i15 I
positions nearly coincide with those of the corresponding LTM-AI crystalline alloys [2-4]. It is noteworthy here that the intensity of the lower energy peak relative to that of the higher energy peak is strong for iron, comparable for cobalt and nickel, and weak for copper. This may suggest that the chemical environment about aluminium atoms is not necessarily determined by a statistical distribution of late and early transition metal atoms. Rather, certain preferential atomic bonding, such as Fe-AI in Fe-Zr-AI and Zr-AI in Cu-Zr-AI systems, may be present in these ternary glasses. In Fig. 2, soft X-ray emission A1 Kfl and Si Kfl spectra of (Pd33Zr67)s0A12o and (Pd33Zr67)9oSi]0 res p e c t i v e l y are shown and compared with the X-ray photoelectron spectrum of Pd35Zr6s. This X-ray photoelectron spectrum is not modified appreciably on alloying with aluminium or silicon. The A1 K# spectrum manifests two peaks at - 2 . 0 and - 4 . 7 eV. The former is attributable to A1 3p-Zr 4d bonding as stated above, while the latter arises from A1 3p-Pd 4d bonding. This peak profile appears to be consistent with the fact that the X-ray photoelectron spectrum manifests Zr 4d- and Pd 4d-derived bands at - 0 . 5 eV and - 4 . 0 e V respectively; in a transition metalnon-transition metal system, p-d bonding states are
-15
-i0
I
-5
E-E
F
!
!
0
5
[eV]
Fig. 2. Soft X-ray emission AI Kfl spectrum of (Pd33Zr67)soA120 and Si K# spectrum of (Pd33Zr67)905ilo, compared with the Xray photoelectron spectrum of Pd35Zr65: , Si K# spectrum of Zr85Si t 5-
formed, in principle, near or below the bottom of the d band of the transition metal [2]. However, this type of two-peak structure cannot be clearly seen in the Si K# spectrum, projecting the partial density of states of the Si 3p band in the glass. It consists of a single asymmetric peak at - 4 . 3 eV. Since a similar but less asymmetric peak is observed in a ZrssSi,5 alloy glass (broken curve), this peak can be ascribed mainly to Si 3p-Zr 4d bonding. It is important to note that, in contrast with the A1-Zr bonding, the Si-Zr bonding is accompanied by a marked increase in the binding energy. The formation of Si 3pPd 4d bonding cannot be clearly recognized. The bonding peak should occur at around - 5.8 eV, since a prominent peak has been observed at this energy in Pd-Si alloy glasses [5]. It may therefore contribute, if at all, to the lower energy tail of the asymmetric spectrum. The above features may be an indication that,
271 trum manifests Ti 3d- and Cu 3d-derived bands at - 0 . 5 eV and - 3.4 eV respectively. The Si Kfl spectrum, however, presents only a single peak at - 3.9 eV. This peak is almost identical with that of a Ti83Si17 alloy glass (broken curve) and hence is attributable to Si 3p-Ti 3d bonding. A small hump is seen on the lower energy side of this peak. It may arise from Si 3p-Cu 3d bonding, because its energy nearly coincides with that of an Si Cu bonding peak ( - 5.2 eV) observed in crystalline Cu-Si alloys [2, 3]. The above result suggests that the silicon atoms in this ternary glass are preferably bound to the sites whose major neighbours are titanium atoms.
Cu30Ti70
...I-,. C
:5
4. Summary and conclusion
(Cu33Ti6?)80AI20
f,.i_...i
At K B
>-,. I-.. z w ~-z
(Cm3T7)9OSi Si KB Ti835i17 |
-15
I
-10
!
-5
!
!
0
5
E-E F r e v ' l Fig. 3. Soft X-ray emission AI Kfl spectrum of (Cu33Ti67)soA12o
and Si Kfl spectrum of (Cu33Ti67)905ilocompared with the Xray photoelectron spectrum of Cu3oTi7o: , Si Kfl spectrum of Ti83Si17.
By measuring soft X-ray emission band spectra of ternary L T M - E T M - M (M = A1 or Si) alloy glasses, the nature of chemical bonding and short-range structure about aluminium and silicon atoms in the glasses have been studied. It has been shown that, in the L T M - E T M AI glasses, the aluminium atoms are in an environment of both late and early transition metal neighbours; of the late and early transition metals investigated, aluminium appears to have the most preference for iron, intermediate for zirconium and titanium, and least for copper. In contrast, in the L T M - E T M - S i glasses, the silicon atoms are surrounded preferably by the early transition metal neighbours irrespective of the species of the late transition metals. The above trends in the chemical affinity ofaluminium and silicon for the late and early transition metals seem to have strong relevance to the formability and electronic properties of these ternary alloy glasses [6].
Acknowledgments while the aluminium atoms are surrounded by both zirconium and palladium neighbours, the silicon atoms are placed on the sites surrounded mostly by zirconium atoms. Quite a similar conclusion has been derived for Ni-Zr~(AI, Si) alloy glasses [6]. Figure 3 shows soft X-ray emission AI Kfl and Si Kfl spectra of (Cu3~Ti67)soA12o and (Cu33Ti67)9oSilo respectively, together with the X-ray photoelectron spectrum of Cu3oTi7o. The A1 Kfl spectrum consists of two peaks, one at - 1.8 eV which is related to A1 3pTi 3d bonding and the other at - 3.8 eV due to AI 31~ Cu 3d bonding. This assignment is based on the fact that an AI Ti bonding peak has been observed at - 2 . 4 eV in a Ti3A1 crystal (not shown in the figure) and, in addition, an AI-Cu bonding peak has been observed at - 5.0 eV in Cu A1 crystalline alloys [2-4]. The above spectral feature of the ternary glass is consistent with the fact that the X-ray photoelectron spec-
The authors acknowledge Professor K. Suzuki and Dr. T. Fukunaga for providing us with ribbon samples of the Ti-Si and Z ~ S i alloy glasses. They also express sincere thanks to Professor U. Mizutani and Mr. Y. Yamada for cooperation in preparing the glass samples and for valuable discussions.
References 1 F. E. Luborsky (ed.), Amorphous Metallic Alloys, Butterworths, London, 1983. 2 K. Tanaka, M. Matsumoto, S. Maruno and A. Hiraki, Appl. Phys. Lett., 27(1975) 529. 3 K. Tanaka and A. Hiraki, Jpn. J. Appl. Phys. 17, Suppl. 2 (1978) 121. 4 K. Tanaka, T. Saito and M. Yasuda, J. Phys. Soe. Jpn., 52 (1983) 1718. 5 K. Tanaka, T. Saito, K. Suzuki and R. Hasegawa, Phys. Rev. B, 32 (1985) 6853. 6 Y. Yamada, Y. Itoh., U. Mizutani, N. Shibagaki and K. Tanaka, J. Phys. F, to be published.