Photon Factory Activity Report 2004 #22 Part B (2005)
Materials Science

10B/2003G230

Conduction pathways in AgI-doped chalcogenide glasses
Takeshi USUKI*1, Takaaki FURUKAWA1, Yohei ONODERA1
Toshio NASU2, Masaki SAKURAI3
1
Depertment of Material and Biological Chemistry, Yamagata Univ., Yamagata 990-8560, Japan
2
Faculty of Education, Yamagata Univ., Yamagata 990-8560, Japan
3
Institute for Materials Research, Tohoku Univ., Sendai 980-8577, Japan

Experimental procedure
Appropriate amounts of AgI, As and Se, with thosecompositions expressed as (AgI)x(As2Se3)1-x with x ≤ 0.6,
were sealed within an evacuated quartz ampoule andthoroughly mixed in a rocking furnace at 700 °C. Then,the melts were quenched rapidly in an ice-water mixture.
EXAFS studies for amorphous samples were carriedout at BL-10B (for Ag and I K-edges) stations in KEK-PF.
The intensity of the incident beam, I0, and that of thetransmitted beam, I, were measured using ionizationchambers.

compared with that for β-AgI. Nevertheless, reasonably
good signals were obtained up to 16 Å-1. The
corresponding Fourier transforms F(R) has one main peakat round 2.5 Å for the glasses (Fig. 2), the position ofwhich is very similar to the case of β-AgI, although aslight disagreement in the signal phase between glasses
and β-AgI can be seen in k3χ(k). It is worth remarking
that the peak of a second coordination shell, which isclearly observed at around 4.3 Å in F(R) for β-AgI andcorresponds to the I-I correlation of sub-lattices,completely vanished in the glass state. This fact seems tobe attributed to the structural disorder of the I-I sub cages
in the glasses.
20|F(R)| (a.u.)

Introduction
Superionic conducting glasses containing Ag ions havereceived much attention because of scientific interests intheir conduction mechanism as well as their application insolid-state electrochemical devices1. Although manydifferent kinds of glass systems have been structurallyinvestigated, especially in silver oxysalt systems, theionic diffusion mechanism is not yet fully understood. In
addition, there has been a lack of information concerning
physical properties and detailed microscopic structure for
AgI-doped ‘non-oxide’ glass systems. The present report
describes results of the EXAFS analysis in AgI-As2Se3glasses, in order to discuss the conduction mechanism inAgI doped non-oxide glasses.

β -AgIx = 0.40x = 0.60

1510500123456R / A

Fig. 2 I K-edge distribution functions for(AgI)x(As2Se3)1-x glasses

503k χ(k) (a.u.)

10-5β-AgIx = 0.40x = 0.60-10048k / A

1216-1

Fig. 1 I K-edge EXAFS functions for (AgI)x(As2Se3)1-xglasses
ResultsFigure 1 shows the EXAFS oscillations observed
around the I K-edge for (AgI)x(As2Se3)1-x glasses together
with those for β-AgI. Because of the structural disorder ofthe glasses, signal intensities for the glasses were weaker

The results of a least-squares fitting analysis for theEXAFS data including Ag, As and Se K-edges2 allow us
to predict that the structure model for AgI-As2Se3 glasses
can be proposed to be a pseudo-binary mixture of theAs(Se1/2)3 network matrix and AgI-related conduction
pathways, which would be responsible for the highmobility and diffusivity of Ag+ in the present glasssystem.
References[1] T. Minami, K. Imazawa, M. Tanaka, J. Non-Cryst.
Solids 42 (1980) 469.
[2] T. Usuki, K. Nakajima, T. Furukawa, T. Nasu, M.
Sakurai, PF Activity Report 2003 #21 Part B (2003) 170.
* usuki@sci.kj.yamagata-u.ac.jp

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