IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
(series-2). A temperature cycle
imposed on the sample after it
exited the RuTe 2 single phase
region revealed that I(Te 2+
) at
980 K was consistent in both
decreasing and increasing
temperature directions.
The results of series-1
experiments yielded a
p(Te 2 )-T relation for Te 2 (g) and
∆rHm o (T) for the incongruent
vaporization reaction: RuTe 2 (s)
= Ru(s) + Te 2 (g). The series-2
experiments, mainly performed
to be able to determine the Teand
Ru-rich boundary
compositions of RuTe 2 phase,
gave somewhat disconcerting
results, the Te-rich boundary
values showing some
dependence on the starting
composition or the amount. The
Ru-rich boundary values are
relatively consistent (i.e. within
the uncertainties associated
with such experiments) and
close to stoichiometric value,
which we assumed while
evaluating the series-1 data. It
is now proposed to conduct a
few more experiments on at
least two newer compositions
(one, only slightly Te-rich
relative to the hitherto reported
Te-rich boundary composition,
and the other 73.5 at.% Te) to
examine the reason for
dependence of Te-rich
boundary values on the starting
composition.
log{[I(Te 2
+
)/I
o
](T/K)}
log{[I(Te 2
+
)/I
o
](T/K)}
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
605 K
Te 2
+
Te +
9.5 10.0 10.5 11.0 11.5 12.0
700 K
635 K 650 K
10 4 (K/T)
820 K
750 K
900 K
980 K
980 K
(RuTe 2
+Te) RuTe 2
(Ru+RuTe 2
)
400 600 800 1000 1200 1400 1600
Time (minutes)
Temp range : 860-1030 K
Fig.1 Temperature dependence of ion intensitied of T e
+
and T e2
+
at ~30 ev
980 K
980 K
960 K
1000 K
Fig.2 variation of 1 (Te 2+
) as a function of time at different temperatures;
composition of the sample 69.5 at % Te
172 BASIC RESEARCH