Modern Solid State NMR Strategies for
the Structural Characterization of
Disordered Materials
Hellmut Eckert
Instituto da Física São Carlos
Universidade de São Paulo
Disordered States of Matter
Non-Stoichiometric Compounds
Plastic Crystals
Glasses, Gels, Ceramics
Nanocomposites
Composition
Preparation, Processing
Structure
Dynamics
Properties
O estado vítreo: aspectos termodinâmicos
gás
transição
vítrea
Entalpia, volume
vidro
cristal
Temperatura
líquido
Distance distributions in states of matter
Ion Conducting Glasses
Network formers:
Network modifiers:
SiO2,B2O3,P2O5,Al2O3
alkaline, alkaline-earth or
silver oxides
Short Range Order
network
former
network
modifier
B
O
M
directly bonded neighbors
Coordination numbers and symmetries
Site quantification
200-300 pm
Medium-range Order in Glasses
B, Si, P
O
Li-Cs
Network former connectivity
Network former-network modifier correlation
Spatial distribution of modifiers
300-600 pm
Nano- and Microstructure
• Chemical Segregation,
• Phase Separation,
• Nucleation/growth
> 1nm
Solid State NMR
Element selective
Locally selective
Inherently quantitative
experimentelly flexible
B0
selective - averaging
E
hn
H =
ΔE = 
B0
HZ + HD + HCS + HQ
Distances
Bonding geometry
Magic Angle Spinning - MAS
B0
zr
  54 . 7
o
nrot
Haniso= A . {3 cos2  – 1}
θ
H =
HZ + HD + HCS + HQ
iso
Interações Dipolares
Anisotropia de Desvio Químico - CSA
Interações Quadrupolares de Primeira Ordem
2nd.
Current Research Agenda
H. Eckert
eckert@ifsc.usp.br
NMR Methods
Development
Glass
Science
Li Ion Battery
Components
Optical
Materials
Catalysts
Biomaterials
SSNMR, ESR
Dipolar
Techniques
Structure
Dynamics,
Sol-Gel
Electrode
Electrolytes,
Ceramics
Luminescent
Ceramics,
Hybrids
FLP, Zeolite
Nanocomposites
Bioceramics
Support
Industry: Corning, Schott, Ivoclar, Nippon Glass
DFG, DFG-SFB, IRTG, BMBF
CNPq Universal, FAPESP, CEPID, CNPq- 1B
Mixed Network Former Effect
In Ion-Conducting Glasses
In a glass system with fixed network modifier content:
How do the physical properties change
when we vary the network former composition ?
Often these changes are non-linear,
requiring fundamental understanding
on a structural basis
Mixed network former effect in the
(M2O)0.33[(P2O5)1-x(B2O3)x ]0.67 – System (M = Li, K, Cs):
Glass Transition Temperatures
800
750
Tg / K
700
650
600
550
M2O =
500
Li2O
450
K2 O
400
Cs2O
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
Mixed network former effect in the
(M2O)0.33[(P2O5)1-x(B2O3)x ]0.67 – System (M = Li, K, Cs)
Activation Energies
-8
1.00
-9
0.95
-10
0.90
EA / eV
log10(DC×cm)
DC- conductivity (300 K)
-11
-12
M2O =
Li2O
-13
K2 O
-14
Cs2O
M2O =
Li2O
K2 O
Cs2O
0.85
0.80
0.75
0.70
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
x(B2O3)
Dynamic characterization by static 7Li NMR
x = 0.4
500 K
480 K
x = 0.0
x = 0.2
x = 0.4
x = 0.6
x = 0.8
x = 1.0
7000
460 K
440 K
6000
420 K
5000
380 K
360 K
340 K
320 K
300 K
n/ Hz
400 K
Single
Network former
4000
3000
2000
Mixed network
former
280 K
260 K
240 K
220 K
200 K
100
50
0
7
-50
( Li) / ppm
-100
1000
0
200
250
300
350

400
450
M. Storek, R. Böhmer, S. W. Martin, D. Larink, H. Eckert, J. Chem. Phys. 2012
500
Structural Issues Regarding the MixedNetwork Former Effect
• Network former speciations
– Coordination polyhedra
– Types of anionic and neutral species present
• Connectivity distributions
– Random Linkages ?
– Connectivity Preferences ?
– Clustering/Phase separation ?
• Competition for the network modifier
– Proportional sharing vs. preferential attraction
• Relation to physical properties
SOLID STATE NMR CHARACTERIZATION
B(3)
B(4)
11B a)
20
10

0
( )/ ppm
P(1) P(2) P(3)
x= 1.0
x = 0.9
x= 0.9
x = 0.8
x= 0.8
x = 0.7
x= 0.7
x = 0.6
x= 0.6
x = 0.5
x= 0.5
x = 0.4
x= 0.4
x = 0.3
x= 0.3
x = 0.2
x= 0.2
x = 0.1
x= 0.1
x = 0.0
-10
20
0

-20
-40
31P
-60
( P) ppm
D. Larink, H. Eckert, M. Reichert, S.W. Martin, J. Phys. Chem. 126, 26162-26176 (2012)
Structural speciation in the
(K2O)0.33[(P2O5)1-x(B2O3)x ]0.67 – system
Struktureinheiten in %
4
B
3
B
2
B
3
P
2
P
1
P
50
40
30
20
10
0
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
x(B2O3)
0 < x < 0.5: P(2) units successively replaced by B(4) units
0.5 < x 1.0: P(3) units successively replaced by B(3) units
Tg-value and network connectedness
0 < x < 0.5: P(2) units successively replaced by B(4) units
0.5 < x 1.0: P(3) units successively replaced by B(3) units
Glass transition temperature
number of bridging oxygen
per network former unit
800
1.7
750
1.6
650
[O]
Tg / K
700
600
1.5
1.4
550
M2O =
M2O =
500
Li2O
450
K2 O
400
Cs2O
1.3
Li2O
K2O
1.2
Cs2O
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
x(B2O3)
11B-
MAS –NMR Spectra of Borophosphate Glasses
50% Ag2O * x P2O5 * (50%-x) B2O3
x=45%
x=40%
x=35%
x=30%
x=25%
BO4
BO3
20
x=20%
10
0
 / ppm
-10
-20
Connectivity with phosphorus ??
Modulation of HD under Sample Rotation
Magic- Angle Spinning (MAS)
31P
+
IS
ˆ
HD
-
Tr
Rotational Echo Double Resonance
(REDOR)
S
+
Titel Y Achse
IS
Hˆ D  D sin( r t ) Iˆz Sˆ z
IS
Hˆ D
Titel Y Achse
11B
+
Tr
I-channel p pulse
Titel X Achse
Titel X Achse
( Iˆz   Iˆz )
REDOR Pulse Sequence
p
p/2
F5
Titel Y Achse
11B
Titel X Achse
31P
S
S0 - S
p/2
=
p
F5
Titel Y Achse
11B
Titel X Achse
31P
0
1
2
[ Tr ]
3
4
S0
S0
Site Connectivities in Borophosphate Glasses:
11B
{31P}-REDOR on
50% Ag2O - 25% B2O3 - 25% P2O5
difference
spin echo with
dephasing
BO4
BO3
spin echo
75
50
25
0
-25
-50
-75
REDOR Pulse Sequence
p
p/2
F5
Titel Y Achse
11B
Titel X Achse
31P
p/2
p
F5
depends on:
Titel Y Achse
11B
Titel X Achse
31P
S
S0
strength of interaction
(# neighbors, distance)
dipolar evolution time
N . Tr
0
1
2
[ Tr ]
3
4
Analysis of REDOR Curves in Glasses
S
S0
( N Tr ) 
1
I ( I  1)p
2
M 2 ( N Tr )
2
2
M2
4  0  2 2


  I  S S ( S  1)
15  4p 
.
2

S
6
rIS
11B{31P}
REDOR of Crystalline BPO4
meas
M2
theo
1.0 M2
2
= 15.8 ± 0.2 kHz
2
= 18.48 kHz
(S0-S)/S0
0.8
0.6
0.4
0.2
0.0
0.0000
Measurement
Simulation
0.0005
0.0010
NTr (s).
0.0015
0.0020
Network connectivity: 11B{31P} REDOR
(S0-S)/S0+ (S0-S')/S0
1,2 x = 0.6
4
11
4
31
6
2 -2
11
3
31
6
2 -2
B
3
B
M2( B(B ){ P}) = 7.6×10 (+/- 10 %) rad s
1,0
M2( B(B ){ P}) = 2.1×10 (+/- 10 %) rad s
0,8
0,6
0,4
S/So = 4/3p M2 (N.Tr)2
M2 ~ Srij-6
0,2
0,0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
N×Tr / ms
M2 = 4-5 . 106 rad2/s2 per B-O-P linkage
No B(3)-O-P connectivity
1,4
Network connectivity
via O-1s XPS:
P-O-P
P-O-B
x = 1.0
x = 0.9
x = 0.8
NBO
B-O-B
x = 0.7
x = 0.6
Constant linewidth
Peak position changing monotonically
Areas consistent with composition
Model compound validation
x = 0.5
x = 0.4
Sauerstoffumgebung in %
x = 0.3
NBO
P-O-P
P-O-B
B-O-B
100
90
80
70
60
50
x = 0.2
NBO P-O-B
B-O-B
x = 0.1
40
30
P-O-P
x = 0.0
20
10
0
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
x(B2O3)
538 536 534 532 530 528 526
Bindungsenergie
Binding
energy [eV]/ eV
Quantification of network connectivity:
Chemical ordering scenario
P-O-B
P-O-P
B-O-B
Concentration [%]
100
80
60
40
20
0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
maximized B(4)-O-P Connectivity
no B(3)-O-P Connectivity
no B(4)-O- B(4) Connectivity; no P(2)2B units
Structure-property correlations in the
(M2O)0.33[(P2O5)1-x(B2O3)x ]0.67 – system
Speciation
electrical conductivities
50
40
30
20
10
-8
log10(DC×cm)
Struktureinheiten in %
4
B
3
B
2
B
3
P
2
P
1
P
-9
-10
-11
-12
M2O =
Li2O
-13
K2 O
-14
0
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
x(B2O3)
Cs2O
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
Charge delocalization near P31B and B4 0P units creates shallow
Coulomb traps, favoring ionic mobility
Summary
Solid State NMR as a tool in complex phosphate glasses
• Quantification of Mixed Network Former Effects
–
–
–
–
Site Quantifications
Connectivity distributions
Network modifier sharing
Structure/Property correlations: Tg, 
• Tendency for heteratomic linkages decreases:
– Borophosphate -> Germanophosphate
– ->Tellurophosphate -> Thioborophosphate
• Other systems studied:
– Alumoborate, Alumophosphate,
– Alumophosphosilicat
Optical Glasses and Ceramics
Waveguides, NLO-materials,
Matrices for RE dopants for potential laser applications
• Aluminophosphate or -borate matrices
• Rare-Earth (RE) ion emitters embedded in
a glassy or ceramic environment
• Luminescence intensity (excited state
lifetime, quantum yield) critically
controlled by RE local environment and
spatial distribution
Fundamental Problem: NMR of fluorescent rare earth ions
is impossible due to their strong f-electron paramagnetism
Structural Magnetic Resonance Approaches
1. NMR analysis of diamagnetic
mimics to RE species.
´45
45Sc, 89Y-NMR
2. NMR analysis of paramagnetic
effects on host constituent
nuclei: HZ and T1
3. EPR analysis of electron-nuclear
dipolar couplings
(studied by ESEEM)
= Sc
RE3+3+, Y3+
1. The Diamagnetic Mimic Approach
NMR properties of the isotopes
nuclide
Spin
% abundance
Q/1028m2
n/MHz (11.7T)
45Sc
89Y
7/2
1/2
100 100
0.22
0
121 24.5
139La
7/2
99.9
0.2
71.2
171Yb
1/2
14.3
0
88.0
175Lu
7/2
97.4
2.8
57.2
89Y
MAS NMR of yttrium aluminoborate glasses
and crystalline model compounds
20(Al2O3)-20Y2O3-60B2O3
11B
MAS NMR of
40-y(Al2O3)-yY2O3-60B2O3 (10  y  25)
Prior to crystallization
BO4
BO33(orthoborates)
BO3(metaborates)
BO32(pyroborates)
H. Deters, A. S. S. de Camargo, H. Eckert, et al. J. Phys. Chem. C 113, 16216 (2009)
11B
MAS NMR of vitroceramics in the
40-y(Al2O3)-yY2O3-60B2O3 system (10  y  25)
YBO3
VC-Y25
VC-Y20
VC-Y15
VC-Y10
YAl3(BO3)4
glassy B2O3
60
40
20
0
-20
-40
11
 ( B) / ppm
No evidence of meta- or pyroborate groups in the vitroceramics
Change in B-O-Al connectivity upon crystallization
detected by 11B{27Al} REDOR
20Y2O3 - 20Al2O3 - 60B2O3
VC-Y20
NTR=0.0093 s
YAl3(BO3)4
1.0
Y20
0.8
S0-S
S/S0
0.6
g-B2O3
S0 and S
VC Y20
0.4
0.2
0.0
30
20
10
11
 ( B) / ppm
0
-10
0.00
0.01
0.02
0.03
NTR / s
43% of the B(3) units are not linked to aluminum in the vitroceramic
Glass - to - vitroceramic transition for the system
40-y (Al2O3) - y Y2O3 – 60 B2O3
70
YAl3(BO3)4
11
B signal fractional area
60
50
B2O3
40
30
20
YBO3
10
0
8
10
12
14
16
18
20
22
24
26
mol % Y2O3
(B2O3)0.6(Al2O3)0.4-y)(Y2O3)y
{(0.8/3) - (2y/3)} YAl3(BO3)4
+ {(8y/3)-0.8/3} YBO3
+ 0.2 B2O3
2nd Approach: NMR Analysis of paramagnetic
effects uponthe constituent matrix nuclei: HZ and T1
H Sol  ω S S Z  ω I I Z  AS Z I Z  BS Z I X
Rapid electron Zeeman state fluctuations (short T1e):
= Fermi + dip + dia
()
(2)
Fermi ~{µB2/kBT}gisoBo r ~ cMr
dip ~ {µB2/kBT}r-3{gzz2- ½(gxx2 + gyy2)}(3cos2-1)
(1)Isotropic shift contribution
(2)Isotropic shift contribution + broadening effects
Al2O3)0.2(Y2O3)0.2(B2O3)0.6 : Nd3+, Er3+,and Yb3+ subst.
Nd3+
Y20Nd0.75
Y20Er0.75
Y20Yb0.75
Y20Nd0.50
Y20Er0.50
Y20Yb0.50
Y20Nd0.35
Y20Er0.35
Y20Yb0.35
Y20Nd0.20
Y20Er0.25
Y20Yb0.20
Y20Nd0.10
Y20Er0.10
Y20Yb0.10
Y20
Y20
60
40
20
0
-20
Yb3+
Er3+
60
-40
40
20
0
-20
-40
Y20
60
40
20
ppm
ppm
0
3000
BO
-40
ppm
3000
3+
Er -doped
BO3/2
3
-20
3+
Er -doped
-
BO44/2
BO
3+
3+
1000
Yb -doped
2000
Yb -doped
LB / Hz
LB / Hz
2000
3+
1000
Nd -doped
3+
Nd -doped
0
0,0
0,2
0,4
0,6
x / mol% RE2O3
0,8
0
0,0
0,2
0,4
0,6
x / mol% RE2O3
0,8
Distribution of the RE ions in the ceramics:
27Al MAS-NMR results
10Y-30Al-60B
YAl3(BO3)4
20Y-20Al-60B
YAl3(BO3)4 in phase mixture
VC-Y20Yb2.0
VC-Y10Yb1.0
VC-Y20Yb1.0
VC-Y10Yb0.5
VC-Y20Yb0.5
VC-Y10Yb0.2
VC-Y20Yb0.2
VC-Y10
60
40
20
0
27
 ( Al) / ppm
-20
-40
-60
VC-Y20
60
40
20
0
-20
-40
-60
27
 ( Al) / ppm
Linewidths and areas of new Al site are proportional to Yb/Y ratio
H. Deters, A. S. S. De Camargo, C. N. Santos, H. Eckert, J Phys. Chem. C 114,14618 (2010)
Linewidth (11B)
2000
Linewidth (27Al)
1600
VC-Y10Ybx
YAB: B(3)-II
Line width ( Al) / Hz
1000
VC-Y10Ybx
(YAB)
1200
27
11
Line width ( B) / Hz
1400
1500
VC-Y20Ybx
YAB: B(3)-II
500
1000
VC-Y20Ybx
(YAB)
800
600
0
0
2
400
4
6
[Yb]/([Y]+[Yb]) / %
8
10
0
2
6
8
10
Peak area (27Al)
12
Linewidth (89Y)
4
[Yb]/([Y]+[Yb]) / %
200
VC-Y20Ybx
(YAB)
100
relative fraction of the
27
paramagnetic Al shift
300
89
Line width ( Y) / Hz
10
VC-Y10Ybx
(YAB)
VC-Y10Ybx
8
6
VC-Y20Ybx
4
2
0
0
2
4
6
[Yb]/([Y]+[Yb]) / %
8
10
0
2
4
6
[Yb]/([Y]+[Yb]) / %
8
10
Apparent Yb/Y ratio in the YAB component of VC-Y20 lower than predicted
preferential location of Yb in YBO3 component
Preferential location of Nd in YAl3(BO3)4 component
3. ESEEM - Electron Spin Echo Envelope Modulation
H Sol  ω S S Z  ω I I Z  AS Z I Z  BS Z I X
90°
90°
90°
t
typical excitation
window
t
t+t
• applied at a particular fixed field strength
• systematic variation of the pulse spacing (t+t)
• Modulation effect results from the simultaneous excitation of allowed (ms=±1,
mI=0) and partially forbidden (ms=±1, mI≠0 nuclear spin-flip) EPR
transitions.
V
 ,
( t   t; t )  1  1  cos (  t )1  cos (  (t
k
2
  B
k  I
 
  
2

 B 
 

 

 I 

 t   t ))
V ges ( t   t; t ) 
 V ( t   t; t )
i
i
2
a = [(I + A/2)2 + B2/4]1/2
ß = [(I - A/2)2 + B2/4]1/2
44
ESEEM Spectra of Yb-doped Glasses in the
System xY2O3-(40-x)Al2O3-60B2O3
10
B
27
Al
11
B = 9 kG
t = 136 ns
B
25Y-15Al
20Y-20Al
15Y-25Al
10Y-30Al
5
10
15
20
25
30
35
40
n / MHz
H. Deters, J.F. de Lima, C. Magon, A.S.S. de Camargo, H. Eckert, PCCP 13, 16071 (2011)
Summary
Solid State NMR as a promising tool in optical glasses
• Strategy for structural studies of rare earth ions in
optical glasses
– Influence of rare earth ions upon the framework structure
– First 45Sc and 89Y NMR in glasses
– First ESEEM of alumoborate glasses
• Study of crystallization mechanism and dopant
distributions in Y-alumoborate vitroceramics
– Substitution preference for Yb3+ ions
Thank you
•
•
•
•
Dr. Heinz Deters
Frederik Behrends
Drs. J. F. de Lima, C. J. Magon (IFSC, USP)
Dr. A.S.S. de Camargo (IFSC, USP)
• SFB 458
• NRW Graduate School of Chemistry
• Fond der Chemischen Industrie
AK Eckert, WWU Münster
Prof. H. Eckert
Prof. H.J. Deiseroth (University of Siegen)
S.T. Kong (University of Siegen)
SFB 458
Thanks for your attention!
31P
PS3Se PS2Se2
PSSe3
PSe4
Increasing Se content
Increasing S content
PS4
MAS NMR of Li7PS5-xSexCl
Resolution of first and second coordination sphere
P-S bonding favored over P-Se bonding
MAS NMR of Li7PS5-xSexI
PS4
PS3Se PS2Se2 PSSe3
PSe4
Increasing Se content
Increasing S content
31P
Clear differentiation of S/Se second coordination spheres
Exceptionally good resolution suggests chalcogen/halogen
51
ordering
…as proven by 77Se NMR
52
Complementary Information using
Halogen NMR
- Only 127I signal of ordered phase is visible,
- In disordered materials EFG too large
- Detection of LiI impurities
Paramagnetic broadening of the 207Pb Signal in
Tm-doped (PLZT) at different levels (wt.% Tm)
undoped
0.1
Stepped-frequency acquisition
of full CPMG pulse trains
Second-moment analysis of
Spikelet intensity distribution
0.5
2.0
800
750
700
2
M2 (ppm )
650
4.0
6.0
600
550
500
450
400
350
-1
0
1
2
4
3
5
6
3+
Amount of Tm (weight-%)
RE segregation
7
3. Echo Decay and Modulation
15Al-65B
B = 6.7 kG
Modulation
T=164 ns
Glass Composition:
0.5Yb2O3-19.5Y2O3-15Al2O3-65B2O3
4K
15Al-65B
B = 6.7 kG
t = 164 ns
T = 4K
0
10
Echodecay Fit
2000
4000
6000
t / ns
B
FT
Modulation
11
0
2000
4000
6000
8000
B
8000
8000
t / ns
Structural
55
Experimental
Result
– Echodecay Fit = Modulation 0
Investigations
of RE
5
10
15
20
n / MHz
25
30
35
40
3. A brief Introduction to EPR-Spectroscopy
The EPR Hamiltonian for solids (simplification):
H Sol  ω S S Z  ω I I Z  SAI
further simplifications:
H Sol  ω S S Z  ω I I Z  AS Z I Z  BS Z I X
Due to the anisotropy of the hyperfine coupling, the nucleus “sees” an additional hyperfine
interaction perpendicular to the quantization direction.
nuclear spin has a different quantization direction if the
electron
spin state is |S> than if it is |S>
As a further consequence, nuclear spin flips (mI ≠0) are partially
allowed because of the anisotropy of the hyperfine coupling (B)
Mixing of electron and nuclear spin states
Structural
Investigations of RE
56
11 possible PnmB and 15 possible BnmB units
Bond valence Considerations
O 0.25P
0.25- O
P
O
B
O
O
P
P32B
O
O
O
O
O
P
O 0.25P
P
O
O
O
P
0.25-
O
P33B
P
O 0.75-
O 0.5-
P
O
O
O
O
P
P
O
P
P
P31B
P
P
O
B(4)
O
O
O
O
B(4)
B(4)
B(4)
B(4)
Competition for the network modifier
100 M O =
2
[QB] [%]
80
60
Li2O
K2O
Cs2O
40
20
0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x(B2O3)
At all compositions, the phosphate attracts a larger part of the network
modifier than predicted by the proportional sharing model.