Preparation and properties of superionic conducting glasses based on silver halides

Journal of Non-Crystalline Solids 56 (1983) 15-26 North-HoUand Publishing Company

15

P R E P A R A T I O N AND P R O P E R T I E S OF S U P E R I O N I C C O N D U C T I N G GLASSES BASED ON SILVER H A L I D E S Tsutomu Department University Sakai-Shi,

MINAMI

of A p p l i e d Chemistry, of Osaka Prefecture, O s a k a - F u 591, JAPAN

A number of new g l a s s e s based on silver halides have been developed. These glasses are shown to be purely ionic c o n d u c t o r s w i t h v e r y high c o n d u c t i v i t i e s c o m p a r a b l e to those of aqueous solutions. Some of the glasses are c o m p o s e d of low m o l e c u l a r structural units, in a limited case no c o n d e n s e d anions being present. A part of the Ag + ions in glass are shown to c o n t r i b u t e to the conduction; Ag + ions surrounded by halide ions are m o b i l e and Ag + ions bound to n o n - b r i d g i n g o x y g e n s w i t h strong partial c o v a l e n c y are less mobile. Structural models are p r o p o s e d to explain such a t r a n s p o r t process of Ag + ions. i. I N T R O D U C T I O N R e c e n t l y a number of new g l a s s e s have been prepared in systems based on silver halides [1-10]. These glasses show three features. First, most of the glasses have e x t r e m e l y high conductivities; at room t e m p e r a t u r e the ionic c o n d u c t i v i t y reaches as high as the order of 10 -2 ~-icm-1 w h i c h is c o m p a r a b l e to the c o n d u c t i v i t y of a q u e o u s solutions of ionic crystals. Such a high c o n d u c t i v i t y is in striking c o n t r a s t to the c o n d u c t i v i t y of normal "insulating" g l a s s e s and, thus, the glasses are r e f e r r e d to as "superionic c o n d u c t ing glasses" [5]. Secondly, the chemical c o m p o s i t i o n of the g l a s s e s is special; so called "glass-forming oxides" are not c o n t a i n e d in some systems of such g l a s s e s [ii]. Even if the systems c o n t a i n g l a s s - f o r m i n g oxides, the g l a s s - f o r m i n g region extends to compositions of very low oxide content [8]. Thirdly, the glass structure is w o r t h noting; many glasses contain no c o n d e n s e d macroanions, but only isolated (monomer) anions [12-14]. In this paper we r e v i e w our r e c e n t data on the glass formation, structure and c o n d u c t i v i t y of these special glasses. Much attention will be paid to the influence of r e p l a c i n g silver iodide by o t h e r silver halides on the c o n d u c t i v i t i e s in order to see the ion t r a n s p o r t process. Structural models are p r o p o s e d for these glasses to e x p l a i n the t r a n s p o r t process. 2. GLASS

FORMATION

AND CONDUCTIVITY

Table I lists the c o n d u c t i v i t i e s of a couple of superionic conducting g l a s s e s together with aqueous e l e c t r o l y t e s and a soda-lime glass. It is e v i d e n t from this table that the c o n d u c t i v i t i e s of the glasses, 75AgI-25Ag2MoO~ and 80AgI'20Ag3P04 (mol%), are more than 10 orders of m a g n i t u d e higher than the soda-lime glass and are comparable to those of aqueous solutions of NaCI and A g N O 3.

0022-3093/83/0000-0000/$03.00 © 1983 North-Holland

Minami/Superionicconductingg~sses

16

Table I.

C o m p a r i s o n of c o n d u c t i v i t i e s at 25°C for some substances Conductivity (S_Zem_Z)

Substance 5% NaCl aqueous solution 5% AgN03 aqueous solution 75AgI-25Ag2MoO~ glass (mol%) 80AgI.20Ag3PO~ glass (mol%) Soda-lime glass

Figure 1 shows the c o m p a r i s o n of c o n d u c t i v i t y at 25°C, ozs, b e t w e e n the glassy and crystallized samples as a function of c o m p o s i t i o n in the system AgIAg2MoO~ [4,14]. The conductivity increases e x p o n e n t i a l l y with increasing AgI content. It is also w o r t h noting that o25 of glasses is higher by 1-2 orders of m a g n i t u d e than that of c r y s t a l l i z e d samples. This fact is a striking contrast to e l e c t r o n i c a l l y conducting materials, in which electrons and holes are scattered by phonons and, thus, the lattice disorder increases the scattering of these charge carriers and c o n s i d e r a b l y lowers the conductivity. Besides their higher conductivities, these superionic conducting glasses have several advantages such as isotropic properties, ease of thin film formation, and the like, w h i c h are inherent to glass. Thus, in solid electrolytes, it is of interest to d e v e l o p g l a s s - f o r m i n g systems with high ionic conductivities.

6x10 -2 2x10 -2 l.lxl0 -2 1.2x10 -z 3x10 - ~

~O 10-2

~O

% u ¥ Glasses

~.o

10-3

., Crystallized ..

I0-'

A

o bulk a pellet I

10

~

20

"'~

I

,

I

30 /~0 Ag 2 Mo 04 (rnol %)

,"

50

Fig.l. C o m p a r i s o n of conductivity at 25°C, ozs, between glassy and c r y s t a l l i z e d samples in the system AgI-Ag2MoO~.

Following the periodic table, Fig.2 shows the oxides, MxOy, in the systems A g I - A g 2 0 - M x O y , for w h i c h glass formation has Deen tested so far [8]. The systems containing the oxides m a r k e d by the filled circles formed glasses. Only crystalline samples were o b t a i n e d for the systems marked by the crosses. The m i x t u r e s containing the oxides m a r k e d by the triangles d e c o m p o s e d on heating. It should be noticed that glasses were produced in systems containing no so called "glass-forming oxides", such as the systems c o n t a i n i n q CrO 3, SeO3, or MoO 3. Table II lists e l e c t r o l y t i c properties of several

superionic con-

T. Minami / Superionic conducting glasses

Ill

IV

V

17

Vl

ill

B203 SiO 2

x SO 3

P205

A

V205 GeO2

CrO 3

Mn207 o 5e 03

As205 MoO 3

A ToO 3 1< W O3

Fig.2.

Glass-forming oxides MxOy in AgI containing glasses, the composition o f w h i c h is e x p r e s s e d as the system AgI-Ag20-MxOy. e:glassy, x:crystalline, a:decomposed

ducting glasses [15,16]. Clearly, the transport numbers of Ag + ions are unity and the electronic conductivities determined by the Wagner D.C. polarization technique [17] a r e s m a l l e r b y 6-7 orders of magnitude than the total conductivity. These glasses are considered to be excellent solid electrolytes. 3. G L A S S

STRUCTURE

Figure 3 shows the IR spectra of glasses in the system AgI-Ag20-MoO3 [12,14]. The composition f o r e a c h s p e c t r u m i s s h o w n in t h e i n s e r t in the figure. Glasses were prepared from AgI, Ag20 and MoO3 except for glass(d), which was prepared from AgI and Ag2MoO4.

Table II. Electrolytic Properties of Several Superionic Conducting Glasses at 25°C.

Composition (mol%)

ot (~-tcm-l)

oe (~-icm-l)

tAg+ ¶

75AgI-25Ag2MoO~ 60AgI.40Ag2MoO~ 80AgI.20Ag3PO~

l.lxl0 -2 6.0x10 -~ 1.2x10 -2

8.7xi0 -9 -4.7x10 -9

0.9996 0.9996 0.9972

0.992 ~ 0.001 0.972 ± 0.021 --

60AgI.30Ag20-10B203 60AgI.40Ag2SeO~ 50AgI.30Ag20.20V2Os 33Agl.33Ag20.33GeO2 50AgBr-25Ag20-25B203

8.5xi0 -~ 3.1x10 -3 1.3x10 -3 1.3x10 -~ 2.6xi0 -3

7.8xi0 -9 ---7.2xi0 -a

0.992~ 0.9988 0.9959 0.9853 --

1.018 0.994 0.988 0.983 0.974

Emf

Tubandt

± ± ± ± ±

0.004 0.010 0.018 0.020 0.037

*Ot: total conductivity, **~e: electronic conductivity, ¶tAg+ : silver ion transport number determined by the electromotive force method and the Tubandt method.

T. Minami / Superionic conducting glasses

18

Glasses on the tie line of the p s e u d o b i n a r y system AgI-Ag2MoO4 show quite similar spectra (a)-(d), i r r e s p e c t i v e of the difference in comp o s i t i o n and raw materials. A b s o r p t i o n maxima in the spectra (a)-(d) lie around 875 cm-l(w), 780 cm-l(s) and 320 cm-l(m, b), which are assigned to vl, v 3, and v 4 modes of MoO~- tetrahedral ions, respectively, as shown in the figure. Glasses (e) and (f), w h i c h contain a little more MoO 3 than the glasses on the tie line, show two additional bands around 600 cm-l(w) and 450 cm-l(vw) which are assigned to Vas and ~s modes of the Mo-O-Mo bond, respectively. This bond results from the presence of condensed ions of MoO t tetrahedra, probably Mo20 ~- ions. We can conclude from these results are c o m p o s e d of isolated, m o n o m e r and that the g l a s s e s c o n t a i n i n g a amounts of Mo20~- ions in a d d i t i o n

that the glasses on the tie line ions only of Ag +, I-, and MoOtlittle more MoO3 include small to the above three.

One structural feature of some of the superionic c o n d u c t i n g glasses is that they contain no condensed macroanions, but consist of low m o l e c u l a r structure units, as m e n t i o n e d above. These glasses are c l a s s i f i e d as "ionic" glasses typified by c o n t a i n i n g one type of singly charged cation, whereas "ionic" glasses known so far, such as sulfates or nitrates, contain at least two types of cations [18]. Other direct evidence of the formation of "ionic" glasses is shown in Fig.4, w h i c h is the result of thin-layer c h r o m a t o g r a p h y of glasses in the system A g I - A g z O - P z O s d i s s o l v e d in 10% (NH4)2CO~ aqueous solutions [13]. A t the right and left side, spots for ortho-, pyro-, tripoly- and t r i m e t a p h o s p h a t e s are shown as standards. The glass with the ratio R = A g z O / P z O s of 3, w h i c h is expected to

WAVELENGTH (2.~m) 20 30 4050 15

10

t

',lJ~ '

sta~td

~ta~rd

(a)'

'

'

?

_L~)

i

,5

I

(e) ~

R=~,OtP~Os

3

2.~

2

1.6

Fi

!

1,5

2

3,3

1.25 1

o.e.

6

f-Fig.4. T h i n - l a y e r c h r o m a t o g r a m of A g I - A g z O - P z O s glasses d i s s o l v e d in 10% (NH4)2COa.

1400 1200 1000

800

i

WAVENUMBER

i

i

i

60O 400 (cm-')

Fig.3. IR spectra of glasses the system AgI-Ag20-MoO3.

i

2OO

in

T. Minami / Superionic conducting glasses

19

(,~,~V ~~ z o

z

i

I

,2~

,~

!

WAVENUMBER Fig.5.

i

~

I

650

(¢m-' )

Influence of cation exchange on IR spectra of AgI-Ag20P205 glasses. (a):blown film of glass 50AgI.33.3Ag2016.7P205 (mol%), (b) and (c) :blown film of the glass dipped in 2% KBr aqueous solution for 1 and 10 sec., respectively, (d):KBr pellet containing 1% of the glass powder, (e) :K4P207 crystals in Nujol mulls.

T. Minami / Superionic conducting glasses

20

140C

14ooi -~-~a-A

E

~ ~-~,--

A a

1200

,2oof

1000 - u j - o-u ~--E° u u _ u _ _

oooF --mO--O0o--o--o--o--

aa z w

= brown

~o/~o

film

800

ao

Boo~

~o

so

--ro--oO~--O--O--CJ-AGI

KBr pellet 2o/~o ~o

4o

60

60 ~0

20

ao

6oo!

z

/o

3'o Ag)O

Fig.6.

Lo

CONTEN T (

s'o

60

6°°1

mol "/. )

2'0

20 ~o 60 ~o

3'0

4'0

~ 3

5'0

60

Ag20 CONTENT(tool %)

W a v e n u m b e r of absorption m a x i m a c h a r a c t e r i s t i c of BO3 (a) and BO~ (O) groups in AgI-AgzO-B203 glasses. The c o m p o s i t i o n s of the glasses m e a s u r e d are shown in the c o m p o s i t i o n triangle insert. Left: blown films (4-15 um thick); Right: KBr pellets containing 1% of the glass powders.

contain no condensed phosphate anions, o r t h o p h o s p h a t e ions only.

is shown clearly to contain

Figure 5 shows the influence of ion exchange of Ag + by K + on the IR spectra [13]. S p e c t r u m (a) is for a blown film of the glass 5 0 A g I . 3 3 . 3 A g 2 0 . 1 6 . 7 P z O s (mol%), while spectra (b) and (c) are for the film dipped in a 2% KBr aqueous solution for 1 and i0 s, respectively. Films dipped in the solution were d e v i t r i f i e d immediately and those immersed for 1 m i n were degraded. Spectra (d) and (e) are, respectively, for a KBr pellet c o n t a i n i n g 1 wt% of the glass powder and for K~P207 crystals in Nujol mulls. The a b s o r p t i o n band at 1065 cm -I, assigned to VasPO3 (terminal PO3 group), is shifted to 1135 cm -I, while the band at 895 cm-*, assigned to ~asP-O-P (bridging P-O-P group), remains unchanged. These results show that ion exchange takes place between Ag + ions in the glass and K + ions in the KBr powder as well as in the KBr solution and that, a c c o m p a n y i n g the exchange, the IR band is shifted toward higher wavenumbers. This shift implies that the strength of the P-O bond in the terminal PO3 groups becomes weaker in the case of Ag + ions being located as counter cations of n o n - b r i d g i n g oxygen anions. Thus, the band shift is in turn evidence for the presence of strong partial covalency b e t w e e n Ag + ions and n o n - b r i d g i n g oxygens. A similar band shift has been observed in the glasses shown in Fig.3 (the system AgI-Ag2Mo04) [12] and the partial covalency probably plays an important role in the formation of "ionic" glasses containing only one type of singly charged cation. Among the g l a s s e s in the systems A g I - A g 2 0 - M x O y shown in Fig.2, m o s t glasses are composed of MO~ tetrahedral structure units like the examples shown in Figs.3 and 5 for glasses containing MoO3 and P2Os, respectively. The glasses containing B203 or Ge02, however, are a few

T. Minami / Superionic conducting glasses

exceptions

21

[8].

Figure 6 shows the wavenumber for the absorption maxima of glasses in the system AgI-AgzO-BzO3 [16,19]; the left figure i s for blown films and the right is for the KBr pellets containing 1 wt% of glass powder. The glass-forming region and glass compositions are shown in the inset figure. The wavenumbers shown by triangles and squares are, respectively, characteristic absorptions for BO 3 and BO~ groups. The figure indicates that every glass is composed of BO3 and BO~ groups even if the glass has the mole ratio AgzO/Bz03 equal to 3. When KBr pellet techniques were used for the IR measurements, the wavenumbers characteristic of B03 groups are shifted toward higher wavenumbers by more than 100 cm -I while those of BO4 groups remains almost unchanged. These results must be caused by the ion exchange between Ag + ions in the glasses and K + ions in KBr powder. Thus, we conclude that the non-bridging oxygens are present in BO3 groups only and Ag + ions strongly interact with the non-bridging oxygens, just as in P205 containing glasses. Figure 7 shows the IR spectra of the glass ratio), compared with those of crystalline hexagonal GeO2 (H, quartz type) and glassy tetrahedral Ge04 structure units, and the

WAVELENGTH

10

(2~0m )

30

AgI'Ag20"Ge02 (mole and glassy GeOz [20]. The GeOz (G) are composed of tetragonal GeO2 (T, rutile

L.O 50

lo" AgI-Ag2Se-~Se 5

~~

,

,

AgI-Aoj.zO- P20 5 .

^

.

OeOz(H)

)T(O G ze

~v

/

,

,g20 ;~0tP2~

-~/1/,~ " t / ' Ag2Se/P2Se 5 I

5"1021

,

,

7 total

Io

10 0

i

I

l

I

800 600 WAVENUMBER

I

l

400 ( c m -I )

I

Fig.7. IR spectra of glass AgI. AgzO.GeO2 (mole ratio) in comparison with GeOz. (H),(G), (T) :hexagonal (quartz type), glassy, and tetragonal (rutile type)GeOz, respectively. (a), (b) :glasses prepared in an sealed ampoule and in a tube with one open end, respectively.

200

,

,

1

1.1022 Ag°ionslcm

,

1.5

,

2.1022

3 inglass

Fig.8. Conductivity at 25°C, O2s vs. total concentration of Ag + ions in the glasses of the systems AgI-Ag2SeP2Ses and AgI-AgzO-P2Os.

Z Minami I Superionic conducting glasses

22

type) consists of octahedral GeO 6 structure units. The glasses (a) and (b) were prepared, respectively, in an evacuated, sealed silica glass ampoule and in a silica glass tube with one open end. There is no appreciable difference in the spectra of glasses (a) and (b). The pattern of the glass spectra are very similar to that of tetragonal rutile type GeO2. These results are explained in terms of the dominant structure units of the glass AgI.Ag20-GeO2 being octahedral GeO6. Tetrahedral GeO4 structure units were reported to coexist when the mole ratio Ag20/GeO2 deviates from unity [20]. 4. ION TRANSPORT PROCESS 4.1. The system AgX-Ag2Ch-PzChs

(X= I, Br, CI; Ch = O, Se)

Among the glass forming systems AgI-Ag20-MxOy shown in Fig.2, two systems containing M x O y = P2Os or B203 formed glasses when AgI was replaced by other silver halides, AgBr and AgCl. Furthermore, when Ag20 and P20s were replaced by Ag2Se and P2Ses, respectively, glasses were obtained in a wide range of composition. Comparison of conductivities between those glasses containing different halide ions (X= I, Br, Cl) or chalcogenide ions (Ch = O, Se) provides useful information on the Ag+ ion transport process in glass. This section presents the results for the systems AgX-Ag2Ch-P2Chs.

Ag'_...~ Agl-Ag-zSe-P2Se5/

/

~o o o

/

/ A

10'

1.10n 5 ~ 1.5 Ag~ions/cm3 fromAgX in glass Fig.9. Conductivity at 25°C, o2s, vS. concentration of Ag + ions in the glass contributed bv the AgX component in the systems AgX-Ag2Ch-P2Chs (X= I, Br, CI; C h = O, Se).

P04 or PSe4

!

, Br, or CI

Fig.lO. Structure model of glasses in the systems AgX-Ag2Ch-P2Chs (X= I, Br, CI; C h = O , Se).

T Minami /Superionic conducting glasses

23

i0 z

lO3 'E lo" % O

~10 5

i

16 4

1!2

Ag20/B2C

I0 s

[3

i/1/3 1-10zz

t o t a l Ag*ionslcm 3 in g l a s s

Fig.ll.

3

2"103

3 4 5 6 7 8 910 Ag° ions/cm 3 from Ag! in gloss

C o n d u c t i v i t y at 25°C, o2s, vs. c o n c e n t r a t i o n of Ag + ions in AgI-Ag20-B203 glasses. left: 025 is plotted against the total c o n c e n t r a t i o n of Ag + ions, right: oz5 is plotted against the c o n c e n t r a t i o n of Ag + ions from the AgI component in the glasses.

In Fig.8, the c o n d u c t i v i t y at 25°C, ozs, is plotted against the total c o n c e n t r a t i o n of Ag+ ions in the glasses of the systems A g I - A g z S e P2Ses and AgI-Ag20-P2Os. The c o n c e n t r a t i o n was calculated from the chemical c o m p o s i t i o n and d e n s i t y of each glass (the data for AgIAg20-P2Os were cited from ref.5). The mole ratio AgzCh/P2Chs and a given content of Ag20 are used as parameters in each c o m p o s i t i o n a l series to show the relation between 025 and the total c o n c e n t r a t i o n of Ag + ions. Linear variations are seen between ~25 and the total c o n c e n t r a t i o n of Ag + ions in each composition series, but 025 changes differently in each series and decreases in some series in spite of the increase in total Ag + concentrations. In Fig.9,02s of the same glasses as in Fig.8 is plotted against the c o n c e n t r a t i o n of Ag + ions contributed to the glasses by the AgI component. In c o n t r a s t to Fig.8, o25 in this case lies on one straight line over the whole range of glass formation in each system, irrespective of the Ag2Ch/P2Chs mole ratio or the Ag20 content. These results clearly indicate that only a part of the Ag + ions in the glass contribute to the conduction. The results for the g l a s s e s in the systems AgBr-Ag20-P205 and AgClAg20-P2Os are also shown in Fig.9 (the data for these glasses were cited from ref.21). Good linearity holds for these glasses also. It should be noted that ozs changes c o n s i d e r a b l y with the replacement of iodide by bromide or chloride ions, but changes slightly with the r e p l a c e m e n t of oxide by selenide ions. These results m u s t imply that Ag + ions interacting with halide ions c o n t r i b u t e to the conduction and Ag + ions interacting with c h a l c o g e n i d e ions do not.

24

T. Minami / Superionic conducting glasses

On the basis of the p r e c e d i n g IR spectra and conductivities, a structural model is presented in Fig.10 which explains the ionlc transport process in these glasses. The glasses are composed of halide ions (hatched circles), PO4 or PSe~ ions (triangles), and Ag+ ions. Two types of Ag + ions are illustrated. One is circled and the other is bared. C i r c l e d ones are surrounded by halide ions and bared ones are tied to the corners (oxygen or selenium) of the triangles with strong partial covalency. This structural model indicates that only the circled Ag + ions contribute to the conduction. The result is a large difference in c o n d u c t i v i t y with the replacement of halide ions.

-! Agx

2

80

-2

gzO

~E

20

aO ( 8 " z/ /0' '3~ 2 1

z.O 60

( 6 ) m~ .........-., ~'~'~

.J

/ (9)W ~

-6

4.2. The system AgX-Ag20-B203 (X= I, Br, C1)

o 01)o~

Figure ii shows the dependence of 025 on the Ag+ ion concentration of g l a s s e s in the system AgI-AgzO-B203 (the data for these glasses are cited from ref. 16) 02s is plotted against the total c o n c e n t r a t i o n of Ag + ions in the left figure; the numbers are the mole ratio A g 2 0 / B 2 0 a for the c o m p o s i t i o n series. In the right figure, o25 is plotted against the c o n c e n t r a t i o n of Ag + ions c o n t r i b u t e d to glass from the AgI component. In the left figure, ozs varies separately for each mole ratio Ag20/B2Oa. In adddition, 02s decreases in spite of the increase in the total concentration of Ag + ions in the glasses with high values of the A g 2 0 / B203 ratios. In contrast to the left figure, all the plots lie on one straight line in the r i g h t figure. These results imply that only a part of the Ag + ions in these glasses contribute to the conduction, just like the case of phosphorus p e n t a c h a l c o g e nide c o n t a i n i n g glasses.

-7

f o

I I

A;~"

AgCL

Ag|

Fig.12. Influence of silver halides on c o n d u c t i v i t y of glasses in the systems A g X - A g 2 0 -B203 (X= I, Br, CI). The numbers in parentheses r e p r e s e n t the glass numbers in the composition triangle insert.

x0

0/

,

Ag

\S I /- .... -: '~

oI

-6-- B--9--Bk ',, I ,~=. ~ ""O"'~/~h~V"B

A~

:

:

0-

6/

\ .0-/B

.-'0-.

,

,,

Fig.13. Structure model of glasses in the systems A g X Ag20-B2Oa (X= I, Br, Cl).

T. Minami / Superionic conducting glasses

25

Figure 12 shows the effect of r e p l a c i n g the halide ions on the conductivity. The numbers in p a r e n t h e s e s in this figure indicate the glass c o m p o s i t i o n shown in the c o m p o s i t i o n triangle insert. In these systems, the g l a s s - f o r m i n g regions are very similar even if the type of A g X is d i f f e r e n t and a comparison of c o n d u c t i v i t y b e t w e e n glasses c o n t a i n i n g the same amounts of AgX, Ag20 and B203 can be made easily. The points c o n n e c t e d by lines r e p r e s e n t o25 values for glasses c o n t a i n i n g the same amounts of AgX, Ag20 and B203. The small difference in o25, at most 1/3 to 1/5, is o b s e r v e d between glasses c o n t a i n i n g d i f f e r e n t types of AgX. Such a small difference is a striking contrast to the P205 c o n t a i n i n g glasses as shown in Fig. 9. B a s e d on the above results, a structural model is p r o p o s e d in Fig. 13 [19], w h i c h explains the conduction process in the A g X - A g 2 0 - B 2 0 3 glasses. As shown in Fig. 6, the glasses in this system are composed of BO 3 and BO 4 groups, but only the BO 3 groups contain n o n - b r i d g i n g oxygens. Three types of Ag + ions are i l l u s t r a t e d in the figure. The circled and bared Ag + ions are similar to those in phosphorus pentac h a l c o g e n i d e c o n t a i n i n g glasses. These two types of Ag + ions can not e x p l a i n the small v a r i a t i o n in a25 w i t h the r e p l a c e m e n t of halide ions. A third type of Ag e ions, d o u b l e - c i r c l e d ones, are shown w h i c h interact with BO~ groups. The BO~ groups are singly charged anions of large ionic radii, the presence of such anions + b e i n g favorable for ionic conduction [21]. The d o u b l e - c i r c l e d Ag ions, thus, contribute to the conduction as+well as the circled Ag + ions. The presence of the third type of Ag ±ons explains why the r e p l a c e m e n t of halide ions changed the c o n d u c t i v i t y only slightly in B203 c o n t a i n i n g glasses, whereas, in the P205 c o n t a i n i n g glasses the change in c o n d u c t i v i t y was large. 5.

S UMMA RY

A number of new glasses based on silver halides have been developed. The following conclusions were drawn: (a) These glasses are purely ionic conductors with e x t r e m e l y high c o n d u c t i v i t i e s comparable to those of aqueous solutions of ionic crystals. (b) The c o n d u c t i v i t i e s of glasses are higher than those of crystallized samples. (c) Some of the glasses are composed of low m o l e c u l a r structure units. In a limited case, no c o n d e n s e d anions are present and only isolated, m o n o m e r ions form the glasses. (d) T e t r a h e d r a l groups are the structural units in those glasses not c o n t a i n i n g B203 or GeO 2 . B203 containing glasses are composed of BO 3 and BO 4 groups while GeO 6 groups are the dominant units in GeO 2 containing glasses. (e) A strong partial covalency exists b e t w e e n the Ag + ions and nonb r i d g i n g oxygens and these Ag + ions are assumed to be less mobile. (f) Those Ag + ions s u r r o u n d e d by halide ions in the glass contribute to the conduction. In B203 c o n t a i n i n g glasses, Ag + ions interacting w i t h BO~ groups also contribute to the c o n d u c t i o n as well as the Ag + ions surrounded by halide ions. ACKNOWLEDGEMENT This work was financially s u p p o r t e d by a G r a n t - i n - A i d from the Ministry of Education, Culture and Science of Japan, and by the Asahi Glass F o u n d a t i o n for c o n t r i b u t i o n to industrial technology.

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~ Minarni / Superionic conducting glasses

REFERENCES [i] Kunze, D., Fast Ion Transport in Solids, Ed. by W. van Gool (North Holland Pub., Amsterdam, 1973) p.405. [2] Chiodelli, G., Magistris, A. and Schiraldi, A., Electrochim. Acta 19 (1974) 655. [3] Kuwano, J. and Kato, M., Denki Kagaku Oyobi Kogyo Butsuri Kagaku 43 (1975) 734 (in Japanese). [4] Minami, T., Nambu, H. and Tanaka, M., J. Am. Ceram. Soc. 60 (1977) 467. [5] Minami, T., Takuma, Y. and Tanaka, M., J. Electrochem. Soc. 124 (1977) 1659. [6] Lazzari, M., Scrosati, B. and Vincent, C. A., J. Am. Ceram. Soc. 61 (1978) 451. [7] Minami, T. and Tanaka, M., J. Solid State Chem. 32 (1980) 51. [8] Minami, T., Imazawa, K. and Tanaka, M., J. Non-Cryst. Solids 42 (1980) 469. [9] Tuller, H. L., Button, D. P. and Uhlmann, D. R., J. Non-Cryst. Solids 40 (1980) 93. [i0] Minami, T., Katsuda, T. and Tanaka, M., Solid State Ionics 3/4 (1981) 93. [ii] Minami, T., Nambu, H. and Tanaka, M., J. Am. Ceram. Soc. 60 (1977) 283. [12] Minami, T., Katsuda, T. and Tanaka, M., J. Non-Cryst. Solids 29 (1978) 389. [13] Minami, T., Katsuda, T. and Tanaka, M., J. Phys. Chem. 83 (1979) 1306. [14] Minami, T. and Tanaka, M., J. Non-Cryst. Solids 38/39 (1980) 289. [15] Minami, T., Katsuda, T. and Tanaka, M., J. Electrochem. Soc. 127 (1980) 1308. [16] Minami, T., Ikeda, Y. and Tanaka, M., J. Chem. Soc. Japan, Chem. Ind. Chem. (1981) 1617 (in Japanese). [17] Wagner, C., Proc. C.I.T.C.E. VII (1955) 361. [18] Rawson, H., Inorganic Glass-Forming Systems (Academic Press, London, New York, 1967) Chap.13. [19] Minami, T., Ikeda, Y. and Tanaka, M., J. Non-Cryst. Solids 52 (1982) 159. [20] Minami, T., Imazawa, K. and Tanaka, M., J. Am. Ceram. Soc. 63 (1980) 627. [21] Minami, T. and Tanaka, M., Rev. Chim. Min~r. 16 (1979) 283.