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Structural and atomic effects in lanthanum LII, LIII EXAFS spectra of chalcogenide materials
Physica B 158 (1989) 39-40 North-Holland, Amsterdam
39
STRUCTURAL AND ATOMIC EFFECTS IN LANTHANUM LI I,LI I I EXAFS SPECTRA OF CHALCOGENIDE MATERIALS 5. Benazeth
’ J*,
M.H. Tuil ier ’ Jo, M. Gui ttard*
I -LURE,BBtiment 2090, Universi te de Paris-Sud, F-9 1405 ORSAY FRANCE 2-Universite de Paris V, F-75270 PARIS FRANCE 3-Universi te de Haute-Alsace, F-68093 MULHOUSE FRANCE Abstract:
771e complete analys/sof lam'hanum1 tXAfS spectra /?Ivarious
compounds of La-Ga-O-S system /s presented lt includesthe structural determination of thenef&Yk3ourhoodoflanthafkzm and the firstevidenceand htefpfetationof the atomic resonancessituatedat /HeVabove the L// andL///edgesasdoubleexcitations involvingtneZpand4de/ectfo~s
Introduction:The gallium environment in La-Ga-S and La-Ga-O-S glasses has been studied by EXAFS !We conclude that in both,Ga-S and Ga(O-S) are the unit former of glassesThe lanthanum Llll and LII spectra are more complicated : they present an atomic resonance superimposed to EXAFS. Materials and experimentsThe La-Ga-O-S system, which is governed by two parameters (n=Ga/Ga+La and m=O/O+S),has been studied over all the vitreous regionThe data have been registered at DCI (LURE-France).Harmonics were removed in La L absorption region (5200-6200 eV).Transmitted radiation was detected by ionization chambers filled by He/Ne and air. Analysls of the EXAFS spectra:The LI II EXAFS spectrum of one glassy composition (m=0.45,n=0.64), presented on the figure 1 exhibits damped EXAFS,and at 124 eV above Eo (table I) a broad asymetrical structure, labelled X,.Above the LII edge, a similar energy (labelled crystalline
structure
is observed at the same relative
X,1. X, and X2 are observed for all the studied
compoundsfourier
analysis
showed
that
glassy and
X, and X2 are
not
EXAFS:The FT of the X(E) spectra show only one well-defined shell corresponding to oxygen and sulfur first neighbours (fig. Z).The smoothing of that structure over 37 eV (table 1) reduces within a similar ratio the amplitude of the FT over all the range of the space distance ! Structural effects:ln the sulfide La-Ga-S glasses (we found no structural change around La and Ga atoms (around Ga:4 sulfur atoms at 2.27 A;around La:7 sulfur atoms at 2.93 A).ln La-Ga-O-S glasses, structural changes are proved, 0921-4526/89/$03.50 @ Elsevier Science Publishers (North-Holland Physics Publishing Division)
B.V.
S. Benazeth
40
et al./Lanthanum
HI.
HII
EXAFS
spectra
081 iii
,‘\
z
I
GLASS
M-O 45 N-O.64
mges
Xl
II I
,i’\
_
Observea
I E.’
L III
El i
ii-‘l
‘.”
2 3
km hX, 300.0
i
‘E W
4
X,
E.5
5485
f 1
5488 5
!@5
e
B
CRYSTAL
x
y
x
BLISS
U-O.14
W-O.
+
+
+
SLASS
M-O.49
14
NIY.”
Ea
1
bd
_LTable
I:LII.LI11
I
L III cage 2G5 46” 2p5 4u;o
5609
t I
37
t5
124
t2
5891.5
?I
5894.4
to5
5899 B
TranSltlOll
lev)
5492
XI
fwe
; GE
Energy
structures ‘“VI
2p5 ~9
(2P3,21
ia
c~P:,~;
cd
2p54610(2~
l/2) 5d
/2D5‘d0(2P,,21id
! I ~ 2D5‘wg(2P,,2’cd
39
15
1245
?2
I17
4. 6
40
2~~ 4d9
and N1V.V
cf
t II cage
6016
4
5d
(2P 3/2)
transttions
from
cr
z$h”+‘s.)
gI-OUt-Id State Of La3’ (I Kaken at the lnflexlon pomt.(2C,ken at the maxlmum.(3ldetenn~nat~on of the ~onuat~on I~m~ts of La+ with a 2p core nole.(4hergy range of the resonance mvolvmg 44 Shell.(5)relatIve energy of X,,X2,1aken from E.,Cb)from ref 2
especially for larger m with n fixed (fig.2I.The La-S mean distance increases and N(O+S) around Ga atoms decreasesBoth La and Ga are surrounded by oxygen and sulfur anions. Atomic effects : We show that X, and X2 come from electronic transitions involving the 2p and 4d electronsDue to the width of the 2p core-level and to are excitations edges above La L effect&double solid-state surprising.However,MIV-MV and NIV,V absorption of lanthanum are known to have an atomic character.The latter is similar in solid and vapor’ :the 4d1*-4dg4f transition is shifted from the 4d threshold (105 eV) and a “giant” resonance is observed,with a maximum at 1 17 eV (4d’*-4dgCf transitions).The shapes of X, and % are quite similar to that of the NIV,V resonance in the far U.V. region:same asymetrical profile and same energy range of 40 eV. We substracted the energy of the NI V,V resonance maximum CI 17 eV) to the X,and X2 maxima
(5609
and 6016
ionization
limits
(table
2p64d10 ‘S. ground state
eV).We obtained
l).Thus
acceptable
values
X, and X2 are attributed
of La 3+ to 2p54dg cdcf
‘P, excited
for 2p54d”
to transitions states
Cd from
of La ‘+ ?
I-S. Benazeth, M.H. Tuilier, A.M. Loireau-Lozac’h, H. Dexpert,P. Lagarde, Flahaut, submitted to J. Non-Cryst. Solids ( 1988). 2-E.R. Radtke, J. Phys. 8 12,L7 I ,L77 ( 1979). 3-M.H. Tuilier and S. Benazeth, to be published in Phys. Rev B( 1988).
J.
39
STRUCTURAL AND ATOMIC EFFECTS IN LANTHANUM LI I,LI I I EXAFS SPECTRA OF CHALCOGENIDE MATERIALS 5. Benazeth
’ J*,
M.H. Tuil ier ’ Jo, M. Gui ttard*
I -LURE,BBtiment 2090, Universi te de Paris-Sud, F-9 1405 ORSAY FRANCE 2-Universite de Paris V, F-75270 PARIS FRANCE 3-Universi te de Haute-Alsace, F-68093 MULHOUSE FRANCE Abstract:
771e complete analys/sof lam'hanum1 tXAfS spectra /?Ivarious
compounds of La-Ga-O-S system /s presented lt includesthe structural determination of thenef&Yk3ourhoodoflanthafkzm and the firstevidenceand htefpfetationof the atomic resonancessituatedat /HeVabove the L// andL///edgesasdoubleexcitations involvingtneZpand4de/ectfo~s
Introduction:The gallium environment in La-Ga-S and La-Ga-O-S glasses has been studied by EXAFS !We conclude that in both,Ga-S and Ga(O-S) are the unit former of glassesThe lanthanum Llll and LII spectra are more complicated : they present an atomic resonance superimposed to EXAFS. Materials and experimentsThe La-Ga-O-S system, which is governed by two parameters (n=Ga/Ga+La and m=O/O+S),has been studied over all the vitreous regionThe data have been registered at DCI (LURE-France).Harmonics were removed in La L absorption region (5200-6200 eV).Transmitted radiation was detected by ionization chambers filled by He/Ne and air. Analysls of the EXAFS spectra:The LI II EXAFS spectrum of one glassy composition (m=0.45,n=0.64), presented on the figure 1 exhibits damped EXAFS,and at 124 eV above Eo (table I) a broad asymetrical structure, labelled X,.Above the LII edge, a similar energy (labelled crystalline
structure
is observed at the same relative
X,1. X, and X2 are observed for all the studied
compoundsfourier
analysis
showed
that
glassy and
X, and X2 are
not
EXAFS:The FT of the X(E) spectra show only one well-defined shell corresponding to oxygen and sulfur first neighbours (fig. Z).The smoothing of that structure over 37 eV (table 1) reduces within a similar ratio the amplitude of the FT over all the range of the space distance ! Structural effects:ln the sulfide La-Ga-S glasses (we found no structural change around La and Ga atoms (around Ga:4 sulfur atoms at 2.27 A;around La:7 sulfur atoms at 2.93 A).ln La-Ga-O-S glasses, structural changes are proved, 0921-4526/89/$03.50 @ Elsevier Science Publishers (North-Holland Physics Publishing Division)
B.V.
S. Benazeth
40
et al./Lanthanum
HI.
HII
EXAFS
spectra
081 iii
,‘\
z
I
GLASS
M-O 45 N-O.64
mges
Xl
II I
,i’\
_
Observea
I E.’
L III
El i
ii-‘l
‘.”
2 3
km hX, 300.0
i
‘E W
4
X,
E.5
5485
f 1
5488 5
!@5
e
B
CRYSTAL
x
y
x
BLISS
U-O.14
W-O.
+
+
+
SLASS
M-O.49
14
NIY.”
Ea
1
bd
_LTable
I:LII.LI11
I
L III cage 2G5 46” 2p5 4u;o
5609
t I
37
t5
124
t2
5891.5
?I
5894.4
to5
5899 B
TranSltlOll
lev)
5492
XI
fwe
; GE
Energy
structures ‘“VI
2p5 ~9
(2P3,21
ia
c~P:,~;
cd
2p54610(2~
l/2) 5d
/2D5‘d0(2P,,21id
! I ~ 2D5‘wg(2P,,2’cd
39
15
1245
?2
I17
4. 6
40
2~~ 4d9
and N1V.V
cf
t II cage
6016
4
5d
(2P 3/2)
transttions
from
cr
z$h”+‘s.)
gI-OUt-Id State Of La3’ (I Kaken at the lnflexlon pomt.(2C,ken at the maxlmum.(3ldetenn~nat~on of the ~onuat~on I~m~ts of La+ with a 2p core nole.(4hergy range of the resonance mvolvmg 44 Shell.(5)relatIve energy of X,,X2,1aken from E.,Cb)from ref 2
especially for larger m with n fixed (fig.2I.The La-S mean distance increases and N(O+S) around Ga atoms decreasesBoth La and Ga are surrounded by oxygen and sulfur anions. Atomic effects : We show that X, and X2 come from electronic transitions involving the 2p and 4d electronsDue to the width of the 2p core-level and to are excitations edges above La L effect&double solid-state surprising.However,MIV-MV and NIV,V absorption of lanthanum are known to have an atomic character.The latter is similar in solid and vapor’ :the 4d1*-4dg4f transition is shifted from the 4d threshold (105 eV) and a “giant” resonance is observed,with a maximum at 1 17 eV (4d’*-4dgCf transitions).The shapes of X, and % are quite similar to that of the NIV,V resonance in the far U.V. region:same asymetrical profile and same energy range of 40 eV. We substracted the energy of the NI V,V resonance maximum CI 17 eV) to the X,and X2 maxima
(5609
and 6016
ionization
limits
(table
2p64d10 ‘S. ground state
eV).We obtained
l).Thus
acceptable
values
X, and X2 are attributed
of La 3+ to 2p54dg cdcf
‘P, excited
for 2p54d”
to transitions states
Cd from
of La ‘+ ?
I-S. Benazeth, M.H. Tuilier, A.M. Loireau-Lozac’h, H. Dexpert,P. Lagarde, Flahaut, submitted to J. Non-Cryst. Solids ( 1988). 2-E.R. Radtke, J. Phys. 8 12,L7 I ,L77 ( 1979). 3-M.H. Tuilier and S. Benazeth, to be published in Phys. Rev B( 1988).
J.