Formation region and characterization of superionic conducting glasses in the systems AgIAg2OMxOy

Journal of Non-Crystalline Solids 42 (1980) 469-476 © North-Holland Publishing Company

FORMATION REGION AND CHARACTERIZATION OF SUPERIONIC CONDUCTING GLASSES IN THE SYSTEMS AgI-Ag20-MxOy Tsutomu

MINAMI, Department University Sakai-Shi,

Kazuhiro

IMAZAWA,

and

Masami

TANAKA

of Applied Chemistry of Osaka Prefecture Osaka-Fu 591, JAPAN

Glass-forming regions were determined for the systems AgI-Ag~O-MxOg, where MxOy are B203, Ge02, P2Os, V2Os, As2Os, CrO3, SeO3, and MOO3. The regions were found even in the pseudobinary systems of the simple salt (AgI) and silver orthooxysalts (AgmMOn) except for M=V and Cr. The IR spectra showed that these pseudobinary glasses were composed of discrete Ag +, I-, and MO~- ions only (referred to as "ionic glasses") except glasses containing B203 or GeOz, which included condensed anions of BO3 and B04 groups or GeO4 and GeO6 groups (referred to as "condensed glasses"). The transport number of these glasses was found to be unity. The conductivity, ranging from i0 -s to 10 -2 ~-Icm-I at room temperature, varied exponentially with increasing AgI content within the glass-forming region. The extrapolation to 100% AgI gave the conductivity very close to the value for hypothetical e-AgI at 25°C in every system forming the "ionic glasses" and gave lower values in the "condensed glasses." The higher was the packing density of constituent ions, the larger was the conductivity. From these experimental results it is speculated that the Ag + ion migration takes place in the "diffusion path" composed of iodide ion polyhedra, similar to the case of ~-AgI, and that the incorpolation of oxyanions breaks the path to reduce the mobility and also lowers the concentration of "mobile" Ag + ions. i.

INTRODUCTION

Recently several glasses have been prepared which show extremely high ionic conductivity, say 10 -2 ~-Icm-1 at room temperature, and are referred to as "superionic conducting glasses" [1-6]. Compared to crystalline superionic conductors, these glasses have advantages such as the formation of no-grain boundary disks, isotropic properties, and thin-film formation, inherent to glass. In addition the conductivity of these glasses is higher than that of the crystallized samples with the same chemical composition [3,4]. In the present paper glass-forming regions are determined for various systems containing AgI. The structure, glass transition temperature, ionic transport number, and conductivity, of these glasses are report ed and the conduction process is discussed on the basis of the experimental results.

469

470

T. Minami et al. / Superionic Conducting Glasses

Table

MzOy

B203 SiO2 GeO2 P2Os V2Os As2Os CrO3

MoO3 WO3* SO3" SeO3 TeO3¶ Mn207¶

Starting

preparation

materials

AgI AgI AgI AgI AgI AgI AgI,

Ag20, B203, H3BO3 Ag~SiO~ Ag20, GeO2 AgzO, H3PO~, Ag3PO~, Ag20, V2Os Ag3AsO~ Ag20, Cr03, Ag2CrO~, AgI, Ag20, MOO3, Ag2MoO~ AgI, Ag20, WO3, Ag2WO~ AgI, Ag2SO~ AgI, Ag2SeO~ AgI, Ag2TeO~ AgI, AgMnO~

*Crystalline ¶The mixtures heating.

2.

I. Conditions for glass systems AgI-Ag20-MxOy.

samples of the

in the

Temperature melting

for (°C)

600-800 500-600 450-900 450-500 500-600 500-600 400 500 400-600

Ag~P207 Ag2Cr207

400-600 350-500 200 (deeompd.) 200 (decompd.)

only were obtained. starting materials

decomposed

on

EXPERIMENTAL

The starting materials for glass preparation are listed in Table I, where the systems are expressed in the form of the ternary AgIAg20-MxOy , including the pseudobinary A~I-AgmMO n. Five gram batches were melted in Pyrex or silica glass tubes (OD=I0 mm) at temperatures shown in the table and the resultant melts were poured onto a plate of copper-made box, the inside of the box being cooled with running water. In some compositions an evacuated, sealed silica glass ampoule was preferable for glass formation; in such a case the ampoule containing the melt was immersed in liquid nitrogen for quenching. Slight attack of the melt on the container glass wall was rarely observed in case of melting at high temperatures.

I11

2

IV

V

Vl

Vl]

B~

v,o:. 5

1

6

,o0~ w 03

Fig.l. Glass-forming oxides MxOy in the systems AgI-Ag20-MxOy. (See text for the expression of the composition of each system. e:glass formation, ×:crystalline only, A:decomposed.

Infrared (IR) spectra were measured for blown glass films (5-10 ~m thick) in the range 4000-200 cm -I. Glass transition temperatures (fg) were measured by the differential thermal analysis under nitrogen gas flowing at a rate of 60 ml/min. The transport number of silver ions was measured by the emf and the Tubandt methods. The conductivity was measured at 1 kHz for pressed pellets of pulverized glasses;

T. Minami et al. / Superionic Conducting Glasses

471

the difference in conductivity between the bulk glass and was reported to be small [4,7]. More detailed experimental niques have been published elsewhere [3,4,7-9]. 3.

RESULTS

3.1.

AND

Glass-forming

the pellet tech-

DISCUSSION region

Following the periodic table, Fig.l arranges the oxides, MzOy, in the systems AgI-Ag20-MxOy, for which the glass formation has been tested up to the present. EaGh system is expressed in the form of the ternary AgI-Ag20-MxOy, like Table I, even for the pseudobinary AgI-AgmMOn the system AgI-AgzSe04, for example, is described as the system AgIAg20-SeO8 in this figure (see also (2) z°A Fig.2).

(1),o~ -%

o

o

AOZM~ 4 Ag~ POz. (3)~~zo~eo ('~~

Abe

~oo3

A~C

,o20s

Ag4P207

15)~

Figure 2 shows the glass-forming regions for the ternary and the pseudobinary systems containing AgI. Among these the results containing MoO3 and P20s were cited from refs.8 and 4, respectively. We can see several features from this figure; (i) glasses are obtained even in the systems containing no "glass-forming oxides," as stated in Fig.l, (2) glassforming islands are found in many systems, (3) glass formation is

Table

°\.

S'

o~

ao~

The systems containing the oxides marked by the closed circles formed glasses. Crystalline samples only were obtained for the systems marked by the cross. The mixtures containing the oxides marked by the triangle decomposed on heating. It should be noted that the systems containing no "glass-forming oxides" produced glasses, such as the systems containing CrOs, SeO3, or MOO3.

16) ;ro,~Jo

e ~ A~2C

B

CrO3 A%c~%.A%CrzO, ~

(7)Agl-Ag2SeO& System ,~o

eo

eo

~

zo

!

.

~

~s~ AgVOs

8o 2 5

(8)AgI-Ag3AsO4 System

ioo

Go

eo

Fig.2. Glass-forming regions for several AgI-containing systems. o:glassy, A:partially crystalline, X:crystalline.

II. Transport number of silver ions in several glasses measured by the emf and the Tubandt methods.

Composition (mol %) 75Agl.25Ag2Mo04 60AgI.4OAgzMo04 57AgI.29Ag20.14PzOs 60AgI.4OAg2Se04 80AgI.2OAg3As04 50AgI.3OAg20.2OV20s 33.3AgI.33.3Ag20.33.3Ge02

too

Emf 0.9996 0.9996 0.975 0.998e 0.9952 0.995~ 0.9853

Tubandt 0.992 0.972 0.988 0.994 0.990

± ± + :I: :I:

0.001 0.021 0.003 0.010 0.022

0.988

+

0.018

0.983

+ 0.020

14"12

T. Minami et al. / Superionic Conducting Glasses

possible in the pseudobinary systems of the simple salt (AgI) and silver ortho-oxysalts (AgmMOn, M=Mo, P, Ge, B, Se, As) except for the case of M=Cr and V, and (4) in the case of M=Cr and V, the addition of a small amount of CrO3 and V205 helps the glass formation. 3.2.

Transport

number

of

silver

ions

Table II shows some examples of the transport number measured by the emf and the Tubandt methods. It is evident that the transport number is approximately unity for every glass. Among these a couple of glasses were selected and their electronic transport numbers were determined by the Wagner d.c. polarization method to be about 7 orders of magnitude less than the ionic transport number [i0]. From such results the present glasses are concluded to be excellent ionic conductors. 3.3.

Infrared

8

9

I

I

]WoAVELENGTH15 (~rn ,~0 I

I

30 4050

I

I

I

7o~I. 30~zMoO4

spectra

As noted in section 3.1, glasses have been obtained in the pseudobinary systems of the simple salt (AgI) and silver ortho-oxysalts (AgmMOn); some of these systems are possibly not to include condensed macroanions in glass and thus are interesting in the views of glass formation and structure. 1200

Figure 3 shows IR spectra of glasses in the pseudobinary systems for M=Mo, P, As, Se, Si, and in the ternary systems for M=Cr and V since the binary compositions in these two cases did not form glasses (see Fig.2).

Table III.

Composition (mol %)

70AgI" 30Ag2MoO~

Fig.3. glasses systems ternary

1000

800

600

WAVENUMBER (cm-11

Infrared

400

spectra

200

of

in the pseudobinary AgI-AgmMOn and the systems AgI-Ag20-MzOy

Absorption bands and their assignment for glasses in the pseudobinary systems AgI-AgmMO~ and the ternary systems AgI-AE20-MxO ~ . 75AgI' 25AgzPO~

75AgI. 25Ag3AsO~

70AgI. 30Ag2SeO~

60AgI. 40Ag~SiO~

50AgI. 2OAg20. 3OCRO3

40AgI, 40AgzO. 2OVa05

Absorption

880(w)

maxima

785(vs)

970(vs)

760(vs)

825(vs)

910(vs)

900 860(vs)

780(vs)

720(s,b)

670(s)

325(m,b)

550(s)

385(s)

485(s)

460(s)

420400,(w ) 320(w,b)

( cm- * ) * *

¶ T h e a s s i g n m e n t w a s m a d e on t h e b a s i s o f r e f e r e n c e s * v2 o r s p l i t t e d V~ mode i n CrO~- i o n s . **s:strong, m:medium, w:weak, b : b r o a d , v : v e r y .

11-15.

Assignment g

~l in M0~~s i n MO~VasM-O-M ~

i n MO~-

473

T. Minami et al. / Superionic Conducting Glasses

The assignment of the bands recorded in Fig.3 is shown in Table III; the assignment was made on the basis of refs.ll-15. Evidently the pseudobinary glasses show only the bands characteristic of MO~tetrahedral ions, and the ternary glasses show additionally the antisymmetric stretch of M-O-M groups, owing to the condensation of the tetrahedra, at 720 cm -I for M=Cr and 670 cm -I for M=V. These results lead to the conclusion that the pseudobinary glasses shown in Fig.3 and Table III are composed of discrete Ag +, I-, and MO~4ions only, and the ternary glasses contain condensed anions of the MO4 tetrahedra in addition to the three above; the glasses thus composed of discrete ions only are henceforth referred to as "ionic glasses." Figure 4 shows the IR spectra of glasses in the pseudobinary systems of AgI and ortho-oxysalts for M=Ge and B. In the system AgIAg4GeO4 the absorption bands at about 700 and 880 cm -l are characteristic of GeO~ and GeO~ groups, respectively [16]. In the system AgI-Ag~BO3 the broad bands at about 1020-980 and 1300-1260 cm -I are characteristic of BO4 and BO3 groups, respectively [17]. In contrast to the spectra in Fig.3, these two pseudobinary systems do not thus consist of ortheoxyanions only, but contain Ge06 and GeO4 groups or BO~ and BOs groups. From the spectra and the chemical compositions of these glasses such structural groups are expected to condense to form macroanions; the glasses containing the condensed anions with different coordination numbers of oxygen around the cations are henceforth referred to as "condensed glasses." Table

iV.

Group

U')

:E I--

I

I

I

I

I

Ortho-oxysalt

{ Ag~GeO~ Ag~BO3

I

1400 1200 1000 800 600 400 WAVENUMBER (cm "1) Fig.4. glasses Ag4GeO4

Infrared spectra in the systems and AgI-Ag3BO3.

Structure of glasses in the pseudobinary systems of the simple salt (AgI) and silver ortho-oxysalts (AgmMOn).

i AgzMoO~ AgzSeO~ AgsPO~ Ag3AsO~ Ag~SiO~ II

Z 0

Structure

"ionic glasses" composed of discrete Ag +, I-, and MO~- ions only. "condensed glasses" c o m p o s e d o f Ag +, I - , a n d c o n d e n s e d BO3-BO~ o r GeO~-GeO6 g r o u p s .

200

of AgI-

474

T. Minami et al. / Superionic Conducting Glasses

Table IV summarizes the structural evidence obtained from th 9 IR spectra (Fig.3 and 4) of glasses in the pseudobinary systems of silver iodide and silver orthooxysalts. 3.4.

Glass

transition

temperature

Figure 5 shows the composition dependence of Tg for glasses in the pseudobinary systems of silver iodide and silver ortho-oxysalts. The values of Tg for the "ionic glasses" (M=As, P, Mo, Se) are low, and those for the "condensed glasses" (M=Ge, B) become higher and are very close each other in the whole range of glass formation. These results are consistent with the structural evidence shown in Table IV, indicating that the formation of macroanions causes the increase in Tg. 3.5.

Conductivity

Figure 6 shows the composition dependence of packing densities of constituent ions in glasses for the systems of silver iodide and silver ortho-oxysalts. The densities were calculated from the ionic radius of each ion [18] using the specific gravity of the glasses. In the figure the densities are also plotted for glasses in the pseudobinary system of AgI and silver pyro-phosphate (Ag~P207), which were reported to consist of Ag +, I-, and P20~ions only from the thin-layer chromatography [19] and can be classified as "ionic glasses." It should be noticed that (1) the packing densities of the present glasses are very high compared to those of ordinary silicate glasses [20], (2) the densities increase linearly with increasing AgI content, and (3) the variation of the densities with composition is divided into two groups; the "ionic glass" group with higher densities and the "condensed glass" group with lower densities. The third tendency seems likely from the structural evidence that the matrix with only discrete ions

20C \

15C n Ag4GeO/.' V Ag3BO3 Z~ Ag3AsO4 • Ag3POz, o Ag2MoOL ~10G •Ag25eO 4

[] " ~ n\

X

50

~'Z~

o~

~z~,~

~ e

o4~

,

i 50

,

J , I 60 7o rnol % AgI

,

I 80

,

Fig. 5. Composition dependence glass transition temperatures for glasses in the pseudobinary systems of silver iodide and silver ortho-oxysalt s.

90

of

80

/

: 4/" /@ / ~/

/o

a

OW7c se

V

v

• o • =, •

o

Ag2SeO 4 Ag2MoO4 Ag3P04 Ag3A$O 4 Ag~P20 7

a Ag~G~ 4 60

I

50

60

I

70

I v Ag3~lO3

80

90

I00

mol °1o AgI

Fig.6. Composition dependence of packing densities of constituent ions in glasses for the pseudobinary systems of silver iodide and silver ortho-( or pyro-)oxysalts.

475

T. Minami et al. / Superionic Conducting Glasses

could be packed more densely than the matrix with the "condensed" structure composed of different coordination numbers could be. Figure 7 shows the composition dependence of the condcutivity at 25°C, ~2s, for the same glasses as shown in Fig.6. In the figure the values of the stars 1 and 2 are plotted as the conductivities obtained by extrapolating to 25°C the conductivity us. temperature relation of ~-AgI [21,22].

10 0 ~z

/

/¢+

A Ag3As0~ V • O *

10 -I

g

Ag3B03 Ag&P207 Ag4Ge04 c~-Ag,

1111~/ , /,~ /

"

5 ¥

/~ / •

i i "1

," , ~ / / , / *'s/ / I/I I /

"

,,,I//

~ 1 0 ";

Logarithmic values of ~ z s increase linearly in each system with increasing AgI content, and no maximum was observed in the variation of conductivity with composition, in contrast to the tendency reported for some systems in literature [2,23]. 10-~

It is worth noting that the extrapolated values of O2s to 100% AgI converge to the value (stars 1 and 2) for hypothetical ~-AgI at 25°C in all the systems forming the "ionic glasses," and the extrapolated values for the "condensed glasses" are lower than the converged value above.

,i

II Ag2SeO4 O Ag2~O4 • Ag3PO4

I 50

//~ 60 mol

I 70 80 % Agl

I 90

100

Fig.7. Composition dependence of conductivity at 25°C for glasses in the pseudobinary systems of silver iodide and silver ortho(or pyro-)oxysalts.

The comparison of the results in Fig.7 with those in the deduction that the higher is the packing density, the conductivity. Such a deduction seems unusual in tion in solids.

Fig.6 leads to the larger is the ion migra-

+ . From these experimental results we speculate that the Ag ion migration takes place in th~ "diffusion path" made of I- ion polyhedra, very similar to the Ag ion migration in ~-AgI [24,25]. The incorporation of oxyanions breaks the path to decrease the mobility. Iodide ion polyhedra, which result in the path formation, are expected to be formed more easily in the randomly dense-packed matrix than in the loose-packed matrix; higher conductivities for the "ionic glasses" are likely explained in this way. In previous papers [4,7] we have reported that there are two types of silver ions in superionic conducting glasses; more mobile and less mobile. The incorporation of oxyanions probably reduces the concentration of "mobile" silver ions due to the strong partial covalency between silver and oxygen ions [9,19,26]. The decrease in conductivity with increasing silver oxysalt content is thus caused by the decrease in both mo~ility and concentration of mobile silver ions contributing to the conduction. Acknowledgement This work was supported entific Research from

by the

a Grant-in-Aid for Developmental Ministry of Education, Culture,

and

SciScience,

476

T. Minami et al. / Superionic Conducting Glasses

of Japan, Industrial

and by the Technology.

Asahi

Glass

Foundation

for

Contribution

to

REFERENCES [i] [2] [3] [4] [5] [6] [7] [8] [9] [i0] [ii] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26]

D. Kunze, Fast Ion Transport in Solids, Ed. by W. van Gool, p.405 (1973), North Holland Pub., Amsterdam. A. Magistris, G. Chiodelli, and G. V. Campari, Z. Naturforsch., 31a (1976) 974. T. Minami, H. Nambu, and M. Tanaka, J. Am. Ceram. Soc., 60 (1977) 467. T. Minami, Y. Takuma, and M. Tanaka, J. Electrochem. Soc., 124 (1977) 1659. M. Lazzari, B. Scrosati, and C. A. Vincent, J. Am. Ceram. Soc., 61 (1978) 451. J. P. Malugani, A. Saida, A. Wasnievski, M. Doreau, and G. Robert, C. R. Acad. Sc. Seri~ C, 286 (1978) 177. T. Minami and M.Tanaka, J. Solid State Chem., 32 (1980) 51. T. Minami, H. Nambu, and M. Tanaka, J. Am. Ceram. Soc., 60 (1977) 283. T. Minami, T. Katsuda, and M. Tanaka, J. Non-Cryst. Solids, 29 (1978) 389. T. Minami, T. Katsuda, and M. Tanaka, J. Electrochem. Soc., 127 (1980) 1308. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 3rd ed. part II (1978),John Wiley and Sons, New York. H. Siebert, Z. anorg, allgem. Chem., 275 (1954) 225. P. Paetzold, H. Amoulong, and A. Ruzicka, ~bld., 336 (1965) 278. R. G. Brown and 8. D. Ross, Spectrochim. Acta, 28A (1972) 1263 Randolt-B~rnstein, Atom-u. Molekularphysik, 2 Teil, s.258 (1951). T. Minami, K. Imazawa, and M. Tanaka, J. Am. Ceram. Soc., to be pulished in 63 (1980) Nov.-Dec. issue. T. Minami, N. Kimura, Y. Ikeda, and M.Tanaka, Preprint of the Annual Meeting of the Ceramic Society of Japan, 1980, p.84; E. N. Boulos and N. J. Kreidl, J. Am. Ceram. Soc., 54 (1971) 368. R. C. West, Ed. CRC Handbook of Chemistry and Physics, 54th ed. p.F-194 (1973), CRC Press, Ohio. T. Minami, T. Kstsuda, and M. Tanaka, J. Phys. Chem., 83 (1979) 1306. A. Makishima and J. D. Mackenzie, J. Non-Cryst. Solids, 17 (1975) 147. K. H. Lieser, Z. Phys. Chem. (N.F.), 9 (1956) 302. K. Shahi, Phys. Stat. Sol., 41a (1977) Ii. A. Schiraldi, Electrochim. Acta, 23 (1978) 1039. R. D. Armstrong, R. S. Bulmer, and T. Dickinson, p.269 in Ref.l. D. O. Raleigh, J. Electrochem. Soc., 124 (1977) 1157. T. Minami and M. Tanaka, Rev. Chim. Min6r., 16 (1979) 283.