e.i. kamitsos, r. todorov and c.p. varsamis · structure and dynamics of ion-exchanged glasses e.i....
TRANSCRIPT
Structure and dynamics of ion-exchanged glasses
E.I. Kamitsos, R. Todorov and C.P. Varsamis
Theoretical and Physical Chemistry Institute
National Hellenic Research Foundation, Athens, Greece
17th Universtity Conference on Glass Science&
1st International Materials Institute Workshop on NEW FUNCTIONALITY IN GLASSES
June 26-30, 2005 / State College, Pennsylvania
Outline of presentation
Ion-exchange process: introduction & relevant literature
Structure of ion-exchanged soda-lime-silica glass
Structure of ion-exchanged 30Na2O-70B2O3 glass
ac conductivity spectra of ion-exchanged 30Na2O-70B2O3 glass
Summary
ION EXCHANGE PROCESS IN GLASS
Applications:
- Chemical strengthening of commercial silicate glass
- Altering optical properties of glass (waveguides, micro-optics)
Open Questions:
- Is there a “mixed-alkali effect” in ion-exchanged glasses?
- How are K+ ions accommodated within the glassy network?
- Can any changes in glass structure occur as a result of ion-exchange below Tg?
M.E. Nordberg et. al.
J. Am. Ceram. Soc.
47 (1964) 215.
ion “crowding”
compressive stress
permanent compression
TTg
0,0 0,2 0,4 0,6 0,8 1,0
10-7
10-6
10-5
10-4
10-3
0C
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
310
282
253
239
216
198
180
dc (S
m-1)
K2O/[Na
2O+K
2O]
0,0 0,2 0,4 0,6 0,8 1,0
0,7
0,8
0,9
1,0
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
Ea
dc (
eV
)K
2O / [Na
2O+K
2O]
Mixed Alkali Effect (MAE) in melt-grown glasses
1,7 1,8 1,9 2,0 2,1 2,2 2,3 2,4
-18
-16
-14
-12
-10
-8
-6
-4
dc
=0 exp[-E
a
dc/ kT]
x=0.75
x=0.25
x=0.167
x=0.83
x=0.50
x=1.0
x=0.0
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
(eV)
Ea
dc = 0.72
Ea
dc = 0.90
Ea
dc = 0.95
Ea
dc = 1.00
Ea
dc = 0.95
Ea
dc = 0.91
Ea
dc = 0.76
ln
dc (
Sm
-1)
1000/T (K-1)
G. Tomandl & H.A. Schaeffer, Non-Cryst. Solids, Trans. Tech. Publ., pp. 480-485 (1977).
Ion-exchanged glasses below Tg do not show the MAE; i.e. resistivity shows a linear
behavior throughout the ion-exchanged layer
Ion-exchange below Tg generates a different “mixed-alkali structure” than the melting
process.
Mixed alkali glasses by ion exchange
0,0 0,2 0,4 0,6 0,8 1,0
4
6
8
10
(K/Na) mixed-alkali soda-lime-silica glasses
solid: melt-grown
dashed: ion-exchanged
T=500°C
T=400°C
log (
cm
)
[K2O]/[K
2O+Na
2O]
T=200°C
T=300°C
Mixed alkali glasses by ion exchange, cont.
C. Windisch & W.M. Risen, J. Non-Cryst. Solids, 44, 345 (1981).
(Na/Li) ion-exchanged Li2O-Al2O3-2SiO2 glasses / Raman spectroscopy
Network structure of ion-exchanged glasses is different from that of melt-grown glasses of
the same stoichiometry
Annealing the ion-exchanged glass leads to network structure identical to that of the melt-
grown glass.
S.N. Houde-Walter, J.M. Inman, A.J. Dent & G.N. Greaves, J. Phys. Chem. 97, 9330 (1993).
(Ag/Na) ion-exchanged Na2O-4SiO2 glasses / X-ray absorption fine structure (XAFS)
CN (Na/O) 5, r(Na-O)=2.30-2.32 Å
CN (Ag/O) 2, r(Ag-O)=2.08-2.23 Å (very similar to the environment of Ag in Ag2O)
metal ions create their own characteristic environments in glass.
G. Berg & A. Ludwig, J. Non-Cryst. Solids, 170, 109 (1994).
(Ag/Na) ion-exchanged soda-lime silica glass / ac conductivity (at 102, 103 Hz)
Concentration dependence of ac conductivity shows the typical mixed cation effect.
M. Dubiel, B. Roling & M. Futing, J. Non-Cryst. Solids, 331, 11 (2003).
(K/Na) ion-exchanged soda-lime glass / ac conductivity spectroscopy (10-2 to 106 Hz)
No MAE for ion-exchange below Tg; but presence of MAE for ion-exchange slightly above Tg
Spectral shape of ac conductivity indicates differences in the ion dynamics between glasses
exchanged slightly above Tg and the corresponding melt-grown glasses.
Mixed alkali glasses by ion exchange, cont.
T. Yano, K. Azegami, S. Shibata & M. Yamane, J. Non-Cryst. Solids, 222, 94 (1997).
(Ag/Na) ion-exchanged Na2O-2SiO2 glasses / X-ray photoelectron spectr. (XPS) & 29Si-NMR
Ag ions induced a large charge redistribution on the glass network & an anomalous change
in the distribution of Qn silicate units
formation of Q2 units at the expense of Q3 units, but no Q4 formation.
Y-K. Lee, Y.L. Peng & M. Tomozawa, J. Non-Cryst. Solids, 222, 125 (1997).
(K/Na) ion-exchanged soda-lime glass / FT-IR reflectance spectroscopy
Shift of the 1050 cm-1 peak is much larger than that caused by changes of the fictive
temperature or composition. Thus, the shift of 1050 cm-1 peak is due mainly to the stress.
A new peak at 950 cm-1 develops with ion-exchange and is attributed to formation of non-
bridging oxygen atoms.
EXPERIMENTAL DETAILS…
Glass Compositions Investigated (mol%)
A. Soda-Lime-Silica Glasses
Oxide
Pilkington
float glass (Tg=558 0C)
(FGS0)
Soft glass
tubing
(T0)
SiO2 71.78 71.62
Na2O 12.44 14.02
CaO 8.76 6.19
K2O 0.38 1.03
MgO 5.88 4.82
BaO none 1.50
Al2O3 0.58 1.49
Fe2O3 0.04 0.02
SO3 0.14 0.22
B. Sodium-Borate Glass: 30Na2O-70B2O3
(Tg=477 0C)
INFRARED SPECTRAL MEASUREMENTS:
Specular reflectance at quasinormal incidence (110)
use the same sample for continuous date acquisition in the mid- & far-IR range
(25-5,000 cm-1)
IMPEDANCE MEASUREMENTS:
5Hz -10MHz, f(T)
ELECTRON MICROPROBE ANALYSIS:
K, Na profiles (Na Kα& Κ Κα Χ-rays produced
by a 15 kV, 20-50 nA, e-beam)
GLASS COMPOSITIONS & SPECTROSCOPIC TECHNIQUES
ANALYSIS OF REFLECTIVITY SPECTRA
0 200 400 600 800 1000 1200 1400
0,0
0,1
0,2
0,3
0.2Na2O-0.8SiO
2
Wavenumbers (cm-1)
Re
fle
ctivity
1,0
1,5
2,0
2,5
0 200 400 600 800 1000 1200 1400
0,0
0,5
1,0
1,5
Wavenumbers (cm-1)
x=0.20
n
n k
0
2
4
200 400 600 800 1000 1200 1400
0
2
4
6
Wavenumbers (cm-1)
'
x=0.20
''
0 200 400 600 800 1000 1200 14000
5
10
15
20
Wavenumbers (cm-1)
x=0.20
(
) (1
03 c
m-1)
Kramers – Kronig
transformation
0 100 200 300 4000,0
0,5
1,0
1,5
2,0
2,5
3,0
Li
CsK
Na110
155
215
Abs.C
oeff
. (1
03 c
m-1)
Wavenumbers (cm-1)
Li2O.2SiO
2
Na2O.2SiO
2
K2O.2SiO
2
Cs2O.2SiO
2
0 200 400 600 800 1000 1200 1400
xNa2O-(1-x)SiO
2
1085
502
250
215
773
7351075
970
1050935
x=0.45
x=0.40
x=0.33
x=0.30
x=0.25
x=0.20
x=0.15
x=0.10
AB
SO
RP
TIO
N (
arb
. u
nits)
x=0
1103
470
810
Wavenumbers (cm-1)
Q4
Q3
Q2
Short-range order structure and metal ion-site vibrations
in silicate glasses
Continuous Random Network (CRN) Model
Na2O-SiO2SiO2
Zachariasen, 1932 Warren-Biscoe, 1938
Q0
Qn tetrahedral units in silicate glasses
0 100 200 300 4000,0
0,5
1,0
1,5
2,0
2,5
3,0
Li
CsK
Na110
155
215
Abs.C
oeff
. (1
03 c
m-1)
Wavenumbers (cm-1)
Li2O.2SiO
2
Na2O.2SiO
2
K2O.2SiO
2
Cs2O.2SiO
2
0 200 400 600 800 1000 1200 1400
xNa2O-(1-x)SiO
2
1085
502
250
215
773
7351075
970
1050935
x=0.45
x=0.40
x=0.33
x=0.30
x=0.25
x=0.20
x=0.15
x=0.10
AB
SO
RP
TIO
N (
arb
. u
nits)
x=0
1103
470
810
Wavenumbers (cm-1)
Q4
Q3
Q2
Short-range order structure and metal ion-site vibrations
in silicate glasses
0 100 200 300 4000,0
0,5
1,0
1,5 230
130
(K)
(Na)
Abs. C
oeff
. (1
03 c
m-1)
F1
F2
F3
F4
F5
Wavenumbers (cm-1)
900 1000 1100 1200 1300
0
5
10
15
20
25
[K+][K
+]
F1
F3
F5
Abs. C
oeff
. (1
03 c
m-1)
Wavenumbers (cm-1)
“Synthetic” float glasses
mol% F1 F2 F3 F4 F5
Na2O 12.44 9.61 6.41 3.21 0.38
K2O 0.38 3.21 6.41 9.61 12.44
Q2 + Q4 2Q3
IR SPECTRA OF “SYNTHETIC” MIXED-CATION (Na+/K+) FLOAT GLASSES
)( /
0
24
4 SiOQ
)( -
/ OSiOQ 23
3
)( -
/
2
222
2 OSiOQ
THERMALLY ION-EXCHANGED FLOAT GLASS: K+/Na+
Q2 + Q4 2Q3
glass structure becomes
more homogeneous
T=475 0C
t=16h
900 1000 1100 1200 13000
5
10
15
20
25 Thermal Exchange
in KNO3, T=475
oC
FGS0
FGS1, t=3 h
FGS2, t=16 h
(
10
3 c
m-1)
Wavenumbers (cm-1)
[K+]
0 100 200 3000,0
0,5
1,0
Thermal Exchange
in KNO3, T=475
oC
FGS0
FGS1, t=3 h
FGS2, t=16 h
(
10
3 c
m-1)
Wavenumbers (cm-1)
[Na+]
[K+]
Tg=558 0C
ANNEALING OF ION-EXCHANGED (K+/Na+) FLOAT GLASS
FGS0: pristine float glass
FGS2: FGS0 thermally exchanged
in KNO3 at 475 0C for 16h
FGS2A: FGS2 annealed in air
at 475 0C for 16 h
0 100 200 3000,0
0,5
1,0
FGS0
FGS2
FGS2A
(
) (1
03 c
m-1)
Wavenumbers (cm-1)
[Na+]
[K+]
900 1000 1100 1200 1300
0
5
10
15
20
FGS0
FGS2
FGS2A
(
) (1
03 c
m-1)
Wavenumbers (cm-1)
[Na+] [Na+]
2Q3 Q2 + Q4
glass structure becomes
less homogeneous
Infrared spectra of singe alkali borate glasses
0 200 400 600 800 10001200140016000
2
4
6
8
10
12
14
16
18
M+-Site vibr.
Network def.
BO3 str.BO
4 str.
M2O.2B
2O
3
Li
Na
K
Rb
Cs
Ab
so
rptio
n C
oe
ffic
ien
t (1
03 c
m-1)
Wavenumbers (cm-1)
IR SPECTRA OF “SYNTHETIC” MIXED-CATION BORATE GLASSES
0.3[xK2O-(1-x)Na2O]-0.7B2O3
0 100 200 300 4000,0
0,5
1,0
1,5230 (Na)
172 (K)
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
x=0.0 (Na)
x=0.25
x=0.50
x=0.75
x=1.0 (K)
(
10
3cm
-1)
Wavenumbers (cm-1)
600 800 1000 1200 1400 16000
3
6
9
12
15xK
2O-(0.3-x)Na
2O-0.7B
2O
3
x=0.0 (Na)
x=0.075
x=0.15
x=0.225
x=0.3 (K)
(10
3cm
-1)
Wavenumbers (cm-1)
THERMALLY ION-EXCHANGED 0.3Na2O-0.7B2O3 GLASS: K+/Na+
IR reflectance spectra
0 500 1000 1500 2000 25000,0
0,1
0,2
0,3
0,40.3Na
2O-0.7B
2O
3
offset by 0.07
R
eflecta
nce
Wavenumbers (cm-1)
Ion-exchange in KNO3
at 450 0C for:
t=0 min
t=15 min
t=30 min
t=60 min
THERMALLY ION-EXCHANGED 0.3Na2O-0.7B2O3 GLASS: K+/Na+
IR absorption spectra
600 800 1000 1200 1400 16000
5
10
150.3Na
2O-0.7B
2O
3
(
) (1
03 c
m-1)
Wavenumbers (cm-1)
Ion-exchange in KNO3
at 450 0C for:
t=0 min
t=15 min
t=30 min
t=60 min
0 100 200 300 4000,0
0,5
1,0
1,5
(
) (1
03 c
m-1)
0.3Na2O-0.7B
2O
3
Ion-exchange in KNO3
at 450 0C for:
t=0 min
t=15 min
t=30 min
t=60 min
Wavenumbers (cm-1)
Tg=477 0C
BØ4- BØ2O
-
local structure rearranges
to meet the needs of K+ ions
0 200 400 600 800 1000 1200 1400 16000
4
8
12
16
KNa
0.3Na2O-0.7B
2O
3 (from melt)
0.3Na2O-0.7B
2O
3 ion-exch. KNO
3,
450 oC, 60 min
0.3K2O-0.7B
2O
3(from melt)
(
10
3cm
-1)
Wavenumbers (cm-1)
BØ4-
BØ2O-(C2v)
A1+B2
BØ30 (D3h)
E’
100
101
102
103
104
105
106
107
10-4
10-3
T(°C)
310
296
282
254
268
240
226
217
199
180
0.3Na2O-0.7B
2O
3
f (Hz)
' (S
m-1)
Conductivity spectra of the base glass: 0.3Na2O-0.7B2O3
scaled conductivity spectra
see: B. Roling, A.Happe, K. Funke & M.D. Ingram,
Phys. Rev. Lett. 78 (1997) 2160.
2 4 6 8 10
0,0
0,2
0,4
0,6
0,8
1,0
T(0C)
180
199
217
226
240
254
268
282
296
310
0.3Na2O-0.7B
2O
3
log10
(f/dc
.T) (Hz/Sm-1.K)
log
10 (
'/
dc)
Conductivity spectra of the 0.3Na2O-0.7B2O3 glass ion-exchanged in KNO3
100
101
102
103
104
105
106
107
10-5
10-4
10-3
10-2
Ion-exchanged: KNO3,
450 0C, 30 min.
0.3Na2O-0.7B
2O
3
T (°C)
310
296
282
268
254
240
226
216
198
177
f (Hz)
' (
Sm
-1)
Comparison of conductivity spectra of the base glass 0.3Na2O-0.7B2O3
with those obtained after ion-exchange in KNO3 at 450 0C for 30 min
100
101
102
103
104
105
106
107
10-5
10-4
10-3
10-2
base glass
ion-exch. KNO3
450 0C, 30 min
0.3Na2O-0.7B
2O
3
T(°C)
310
268
216
177
f (Hz)
' (
Sm
-1)
scaled with σdc of the base glass
scaled with low-frequency σdc of
the ion-exchanged glass
K+/Na+ ion exchange below Tg
leads to the development of a highly resistive surface layer
0 2 4 6 8 10-1,0
-0,5
0,0
0,5
1,0
scaled high frequency region
T (0C)
310
296
282
268
254
240
226
216
198
177
0.3Na2O-0.7B
2O
3
t 30 min scaled base glass.opj
log( f / dc
.T) (Hz / Sm-1.K)
log
10( ' /
dc)
Scaled conductivity spectra of the 0.3Na2O-0.7B2O3 glass ion-exchanged
in KNO3 at 450 0C for 30 min
0 2 4 6 8 10
0
1
2
T(0C)
310
296
282
268
254
240
226
216
198
177
0.3Na2O-0.7B
2O
3
3.8.2004 12:41:57t 30 min scaled low freq.opj
log( f / dc
.T) (Hz / Sm-1.K)
log
10( ' /
dc)
10-6
10-5
10-4
10-3
100
101
102
103
104
105
106
107
10-5
10-4
10-3
10-2
30 min15 min
x=0.50
x=0.75
x=0.25
x=1 (K)
x=0 (Na)
T=238oC
x=1 (K)
x=0 (Na)
x=0.75
T=310oC
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
30 min15 min
x=0.50
x=0.25
' (
Sm
-1)
f (Hz)
Comparison of conductivity spectra of mixed alkali glasses
0.3[xK2O-(1-x)Na2O]-0.7B2O3 : melt-grown vs ion-exchanged glasses
1,7 1,8 1,9 2,0 2,1 2,2 2,3 2,4
-18
-16
-14
-12
-10
-8
-6
-4
dc
=0 exp[-E
a
dc/ kT]
x=0.75
x=0.25
x=0.167
x=0.83
x=0.50
x=1.0
x=0.0
0.3[xK2O-(1-x)Na
2O]-0.7B
2O
3
(eV)
Ea
dc = 0.72
Ea
dc = 0.90
Ea
dc = 0.95
Ea
dc = 1.00
Ea
dc = 0.95
Ea
dc = 0.91
Ea
dc = 0.76
ln
dc (
Sm
-1)
1000/T (K-1)
Comparison of activation energies for dc conductivity:
melt-grown 0.3[xK2O-(1-x)Na2O]-0.7B2O3 glasses vs ion-exchanged glasses
1,7 1,8 1,9 2,0 2,1 2,2 2,3
-12
-11
-10
-9
-8
-7
-6
-5
Ion-exch. KNO3, 450
0C
0.3Na2O-0.7B
2O
3
Ea
dc=0.72 eV
Ea
dc=0.84 eV
Ea
dc= 0.93 eV
Ea
dc=0.85 eV
Ea
dc=0.76 eV
ln
dc (
Sm
-1)
1000/T (K-1)
0.3Na2O-0.7B
2O
3
15 min
30 min
120 min
0.3K2O-0.7B
2O
3
melt-grown ion-exchanged
Dielectric spectra in the resistivity representation
Dielectric measurements: apply voltage V(ω)=Vmsin(ωt)
measure current I(ω)=Ιm sin(ωt+δ)
Complex impedance:
Complex resistivity:
d=sample thickness; S=electrode area
Complex conductivity:
)(–)(=)( ///* ωiZωZωZ
m
m
I
VZδZZδZZ =,sin=,cos= **//*/
d
SωZωρiωρωρ )(=)(–)(=)( *///*
)(
1=)(+)(=)( *
///*
ωρωσiωσωσ
22 )]([+)]([
)(=)( ///
/
/
ωρωρ
ωρωσ
22 )]([+)]([
)(=)( ///
/
/
ωσωσ
ωσωρ
100
101
102
103
104
105
106
107
102
103
104
T(°C)
310296282
254
268
240226
217
199
180
0.3Na2O-0.7B
2O
3
f (Hz)
' (
m)
1 2 3 4 5 6 7 8
0,0
0,2
0,4
0,6
0,8
1,0
T(0C)
0.3Na2O-0.7B
2O
3
T=310
T=296
T=282
T=268
T=254
T=240
T=226
T=217lo
g(
dc /
')
log(fdc
/T) (Hz/Sm-1K)
Resistivity spectra of the base glass: 0.3Na2O-0.7B2O3
scaled resistivity spectra
100
101
102
103
104
105
106
107
102
103
104
105 0.3Na
2O-0.7B
2O
3T(°C)
base glass
ion-exch. 15 min
ion-exch. 30 min
KNO3, 450
0C
310
268
226
180
f (Hz)
' (
m)
Resistivity spectra of the 0.3Na2O-0.7B2O3 glass ion-exchanged in KNO3
Resistivity spectra of the 0.3Na2O-0.7B2O3 glass ion-exchanged in KNO3
0
200
400
101
102
103
104
105
106
107
0
200
400
T=310°C
Ion-exch. KNO3, 450
0C,15 min
' ion exchange
'' ion exchange
Fit ion-exchanged layer with 3 comp.
K/Na: 3/1, 1/1, 1/3
K/(K+Na): 0.75, 0.50, 0.25
0.3Na2O-0.7B
2O
3
Ion-exch. KNO3, 450
0C, 30 min
T=310°C
', ''
(m
)
f (Hz)
K/Na dei (μm)
15 min 30 min
3/1 0.7 0.9
1/1 1.4 2.5
1/3 1.7 2.7
de 3.8 6.1
0
200
400
101
102
103
104
105
106
107
0
5000
10000
T=310 °C
Ion-exch. KNO3,
450 0C, 15 min
'
''
Fit '
Fit ''
',
'' (
m)
0.3Na2O-0.7B
2O
3
T=216 °C
f (Hz)
“Annealing” of the 0.3Na2O-0.7B2O3 ion-exchanged glass
K/Na dei (μm)
216 0C 310 0C
3/1 1.2 0.7
1/1 1.0 1.4
1/3 0.4 1.7
de 2.6 3.8
“Annealing” of the 0.3Na2O-0.7B2O3 ion-exchanged glass, cont.
0 1 2 3 4 5 6 7 8 9
2,6
2,8
3,0
3,2
3,4
3,6
3,8
4,0
Ion-exch. KNO3,
450 0C, 15 min
T (0C)
0.3Na2O-0.7B
2O
3
310
296
282
268
253
239
226
217
de (m
)
"Annealing" time (hrs)
Structural aspects of ion-exchanged glasses: soda-lime-silica & sodium-borate
Alkali ion motion in the glass matrix below Tg, caused either by ion exchange and/or
annealing, is accompanied by local structural rearrangements/relaxations involving short-
range order structural units (Cation Induced Relaxations Of the Network, CIRON).
The structural rearrangements depend on the nature of the glass network and the
type of the foreign cation introduced into the glass structure:
Soda-lime-silica glass:
K+/Na+: Q2 + Q4 2Q3
Li+, Ag+/Na+: 2Q3 Q2 + Q4
Sodium-borate glass:
K+/Na+: BØ4- BØ2O
-
The structure of an ion-exchanged glass resembles that of the corresponding melt-
grown mixed alkali glass (i.e. similar SRO structure and nature of sites hosting metal
ions).
SUMMARY
Ac conductivity aspects of ion-exchanged glasses: sodium-borate glass
The resistivity of the ion-exchanged (surface) layer can be described in terms of the
resistivities of melt-grown K/Na mixed alkali glasses.
SUMMARY cont.
ACKNOWLEDGMENT
Univ. of Aberdeen, Scotland: M.D. Ingram, J. Davidson, M.H. Wu, A. Coats
NHRF, Athens: J. Kapoutsis, P. Machowski.
Royal Society / NHRF (exchange program)
General Secretariat for Research and Technology / Ministry of
Development in Greece
European Union (project HPMD-CT-2000-00033).