Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

10B,12C/2005G178

Local structure in AgBr-doped chalcogenide glasses
Takeshi USUKI*1, Yutaka MURAKAMI1, Yohei ONODERA1, Mai SEKINE1
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 AgBr, As and Se, with thosecompositions expressed as (AgBr)x(As2Se3)1-x with x ≤ 0.6,
were sealed within an evacuated quartz ampoule andthoroughly mixed in a rocking furnace at 650 °C. Then,the melts were quenched rapidly in an ice-water mixture.
EXAFS studies for amorphous samples were carriedout at BL-12C (for As and Se K-edges) and 10B (for AgK-edge) stations in KEK-PF. The intensity of the incident
beam, I0, and that of the transmitted beam, I, weremeasured using ionization chambers.

together with those for crystalline AgBr (c-AgBr).
Because of the structural disorder of the glasses, signal
intensities for the glasses were weaker compared withthat for c-AgBr. Nevertheless, reasonably good signals
were obtained up to 16 Å-1. The corresponding Fouriertransforms F(R) has a main peak at round 2.3 Å for theglasses (Fig. 2), the position of which is very different
from the case of c-AgBr. Moreover, it is worth remarking
that the peak of a second coordination shell, which isclearly observed at around 3.9 Å in F(R) for c-AgBr(corresponds to the Ag-Ag correlation of sub-lattices),completely vanished in the glassy state. This fact seems
to be attributed to the structural disorder of the sub cages
in the glassy state.

20AgBr40
AgBr60c-AgBr15| F(R) |Introduction
Many kinds of studies for ionic conducting glasses,
especially for AgI-doped glass systems, have been carriedout from academic and practical point of view [1]. The
fast ion conduction in the AgI-doped glasses is attributed
to their unique structure, which can be modeled as a
mixture of conduction pathways similar to the fast ion
conducting phase of crystalline AgI and rather rigid
chalcogenide networks [2]. On the contrary, there are
few reports on the glass systems containing other silver
halides, such as AgBr and AgCl, in which a rock salt
structure is stable under atmospheric pressure. This paper
will present results of XAFS experiments in AgBr-As2Se3glasses and discuss the local structure in AgBr doped
non-oxide glasses.

10500123456

R / A
15Fig. 2 Ag K-edge distribution functions for(AgBr)x(As2Se3)1-x glasses

1003k χ(k)5-5-10

AgBr40AgBr60c-AgBr-15-20
2468101214

16-1k / AFig. 1 Ag K-edge EXAFS functions for(AgBr)x(As2Se3)1-x glasses
ResultsFigure 1 shows the EXAFS oscillations observed
around the Ag K-edge for (AgBr)x(As2Se3)1-x glasses

The results of a least-squares fitting analysis for theEXAFS data including Ag, As and Se K-edges allow us
to predict that the structure model for (AgBr)x(As2Se3)1-x
glasses can be proposed as the pseudo-binary mixture of
the AsSe3/2 network matrix and tetrahedral AgBr units,
where the short-range order around Ag and Br strongly
differ from the case in crystalline AgBr which has a locksalt structure with the coordination number of 6.
References[1] see for example, T. Minami, K. Imazawa, M. Tanaka,
J. Non-Cryst. Solids 42 (1980) 469.
[2] T. Usuki et al., J. Non-Cryst. Solids 312-314 (2002)
570.
* usuki@sci.kj.yamagata-u.ac.jp

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