Fabrication and electrical and thermal properties of Ti2InC, Hf2InC and (Ti,Hf)2InC

Article abstract of DOI:10.1016/S0925-8388(02)00107-X

In this paper we report on the characterization of predominantly single phase, fully dense Ti₂InC (Ti_1.96InC_1.15), Hf₂InC (Hf_1.94InC_1.26) and (Ti,Hf)₂InC ((Ti_0.47,Hf_0.56)₂InC_1.26) samples produced by reactive hot isostatic pressing of the elemental powders. The a and c lattice parameters in nm, were, respectively: 0.3134; 1.4077 for Ti₂InC; 0.322, 1.443 for (Ti,Hf)₂InC; and 0.331 and 1.472 for Hf₂InC. The heat capacities, thermal expansion coefficients, thermal and electrical conductivities were measured as a function of temperature. These ternaries are good electrical conductors with a resistivity that increases linearly with increasing temperatures. At 0.28 μΩ m, the room temperature resistivity of (Ti,Hf)₂InC is higher than the end members (～0.2 μΩ m), indicating a solid solution scattering effect. In the 300 to 1273 K temperature range the thermal expansion coefficients are: 7.6×10^-6 K^-1 for Hf₂InC, 9.5×10^-6 K^-1 for Ti₂InC, and 8.6×10^-6 K^-1 for (Ti,Hf)₂InC. They are all good conductors of heat (20 to 26 W/m K) with the electronic component of conductivity dominating at all temperatures. Extended exposure of Ti₂InC to vacuum (～10^-4 atm) at ～800 °C, results in the selective sublimation of In, and the conversion of Ti₂InC to TiC_x.

Full text of DOI:10.1016/S0925-8388(02)00107-X

Journal of Alloys and Compounds 340 (2002) 173–179
L
www.elsevier.com/locate/jallcom
Fabrication and electrical and thermal properties of Ti InC, Hf InC and
2
2
(
Ti,Hf) InC
2
a ,
b
b
b
*
M.W. Barsoum , J. Golczewski , H.J. Seifert , F. Aldinger
a
Department of Materials Engineering, LeBow Engineering Center 27-445, Drexel University, Philadelphia, PA 19104-2875, USA
b
Max-Planck-Institut f u¨ r Metallforschung, Stuttgart, Germany
Received 12 December 2001; accepted 8 January 2002
Abstract
In this paper we report on the characterization of predominantly single phase, fully dense Ti InC (Ti1.96InC1.15), Hf InC
2
2
(
Hf1.94InC1.26) and (Ti,Hf) InC ((Ti0.47,Hf0.56)2InC1.26) samples produced by reactive hot isostatic pressing of the elemental powders.
2
The a and c lattice parameters in nm, were, respectively: 0.3134; 1.4077 for Ti InC; 0.322, 1.443 for (Ti,Hf) InC; and 0.331 and 1.472
2
2
for Hf InC. The heat capacities, thermal expansion coefficients, thermal and electrical conductivities were measured as a function of
2
temperature. These ternaries are good electrical conductors with a resistivity that increases linearly with increasing temperatures. At 0.28
mV m, the room temperature resistivity of (Ti,Hf) InC is higher than the end members (|0.2 mV m), indicating a solid solution scattering
2
2
6
21
26
21
effect. In the 300 to 1273 K temperature range the thermal expansion coefficients are: 7.6310
for (Ti,Hf) InC. They are all good conductors of heat (20 to 26 W/m K) with the electronic component of
conductivity dominating at all temperatures. Extended exposure of Ti InC to vacuum (|10 atm) at |800 8C, results in the selective
K
for Hf InC, 9.5310
K
for
2
2
6
21
Ti InC, and 8.6310
K
2
2
2
4
2
sublimation of In, and the conversion of Ti InC to TiC .
 2002 Elsevier Science B .V . All rights reserved.
2
x
Keywords: Intermetallics; Synthesis; Crystal structure; Electrical transport; X-ray diffraction
1
. Introduction
temperatures [5,6]. Some of them are elastically quite stiff
the stiffness of Ti SiC —320 GPa—is almost three times
(
3
2
This paper is a continuation of our work on the
that of Ti metal, with the same density) but are most
readily machinable using manual hack saws or regular high
speed tool steels with no lubrication or cooling required.
They are also excellent conductors of electricity and heat
[1,8–10,12] (Ti SiC has higher electrical and thermal
conductivities than Ti metal). With Vickers hardness values
in the range 2–5 GPa, these compounds are soft compared
to other early transition metal carbides and nitrides. They
are also exceptionally thermal shock-resistant and damage-
tolerant for their stiffness. The latter two characteristics are
traceable to the presence of an active slip system.
syntheses, fabrication and characterization of the so-called
MAX phases [1–15]. These compounds, with the general
formula Mn11AXn where n51 to 3, M is an early
transition metal, A is an A-group (mostly IIIA and IVA)
element, and X is either C and/or N are structurally
related. These layered hexagonal phases—space group
3
2
4
D , P6 /mmc—with two formula units per unit cell, have
6
h
3
been shown to exhibit an unusual and unique combination
of properties [1–15].
There are several reasons these solids represent a new
class of solids. They are the only polycrystalline solids in
which single grains can deform by a combination of slip,
kink band formation and delaminations [1,5,6]. The extent
by which grains can delaminate and deform at room
temperature is unique. Basal plane dislocations, and only
basal plane dislocations, are mobile and multiply at room
This paper deals with the phases Ti InC, Hf InC and
2
2
(Ti,Hf) InC with a Ti/Hf ratio of 1. In the early 1960s, the
2
end members were first synthesized in powder form by
Jeitschko et al. [16], who determined their structure and
lattice parameters. These phases have never been char-
acterized before, and as such could possess unique electri-
cal, magnetic, thermal or catalytic properties for potential
use in many applications. For example, it has recently been
*
Corresponding author. Tel.: 11-215-895-2338; fax: 11-215-815-
760.
E-mail address: michel.w.barsoum@drexel.edu (M.W. Barsoum).
shown that the thermoelectric power of Ti SiC is negli-
6
0
3
2
gible at least over the 300–850 K temperature range
925-8388/02/$ – see front matter
 2002 Elsevier Science B .V . All rights reserved.
PII: S0925-8388(02)00107-X

1
74
M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
[
7,11]. Furthermore, the basal planes of Ti SiC have been
tial scanning calorimeter, DSC, (Netzsch, 404C, Selb,
Germany). The DSC was calibrated using a sapphire
crystal; the calibration and all measurements were carried
out under Ar at a heating rate of 10 K/min. The samples
were cylindrical (5 mm in diameter and |1 mm thick). The
thermal conductivity, D, was measured using a laser-flash
technique. A flat cylindrical (11 mm diameter, 1 mm thick)
3
2
shown to possess very low friction coefficients [15]. Low
friction, good wear resistance and good electrical con-
ductivity is a useful combination of properties that can
potentially be used in rotating electrical contacts such as
motor brushes. These could also potentially be used as
diffusion barriers, or heat sinks in Si-based devices.
This paper is the first report on the synthesis and
characterization of predominantly single phase, dense
samples of Ti InC, Hf InC and (Ti,Hf) InC. The heat
2
4
sample is placed in a vacuum furnace (10
atm) and
heated to a predetermined temperature, at which time, the
front surface is pulsed, for 1 ms, with a 40-J pulse of an
Nd:YAG laser. The increase in temperature on the rear
surface was monitored with a pyrometer and the tempera-
ture versus time curve was digitized and analyzed to
estimate the half-time lag, t1 / 2, between the initial and the
2
2
2
capacity, thermal expansion, thermal and electrical conduc-
tivities of these compounds were measured as a function of
temperature.
stable final temperatures. The D values are calculated
2
2
. Experimental details
assuming, D 5 0.1339d /t / 2. The Ds are then converted
1
to thermal conductivities, k , using the relationship: k
5
tot
tot
Elemental Hf (99.6% pure excluding 2–3.5% Zr), Ti
cpDd.
(
99%), In (99.99%) and graphite (99.9995%)–325 mesh
The electrical resistances were measured using a 4-probe
technique at 290 K, 273.15 K, 77 K and 4.2 K.
powders were used. The purities, based on metal basis
alone, are those specified by the supplier (Alpha Aesar,
Karlsruhe, Germany). The powders were weighed in the
proper stoichiometric ratios, mixed and cold isostatically
pressed using a pressure of 630 MPa. The cylindrical
pellets were sealed in borosilicate glass tubes under
vacuum, placed in a hot isostatic press, HIP, and heated at
3. Results and discussion
3.1. Sample characterization
2
0 8C/min to 700 8C, held at that temperature for 30 min,
According to the XRD patterns (Fig. 1) the samples
were predominantly single phase. The lattice parameters of
the end members are in good agreement with those
measured by Jeitschko et al. [16] (see Table 1). As
expected, the lattice parameters of the solid solution are in
before Ar was introduced in the chamber. The HIP was
then heated at the same rate to 1300 8C, where it was held
for 7 h before cooling. The pressure at 1300 8C was |50
MPa.
The glass was mechanically removed, and the samples
were mounted and polished down to 1 mm diamond for
microstructural evaluation in a scanning electron micro-
scope, SEM. The chemical composition was measured by
electron probe X-ray microanalysis (EPMA) which was
performed on a Cameca SX100 (Paris, France). Measure-
ments were carried out using an accelerating voltage of 15
kV, and a probe current of 20 nA for all but the Hf. For the
Hf, the accelerating voltage was 20 kV with the same
current. The following standards were used for the quan-
titative analysis: pure Ti for Ti, Fe C for C, Hf for Hf and
3
InP for In. The Ka lines were used for the first two and the
La lines for the last two.
The lattice parameters were measured from X-ray
diffraction, XRD, patterns using a diffractometer (D5000,
Siemens/Bruker AXS, Karlsruhe, Germany) with a
position-sensitive detector and Ni-filtered Cu Ka radia-
1
tion. The step size was 0.0088 and the step time was 1 s.
The powdered samples were obtained by drilling into the
center of the samples; Si powder was used as an internal
standard. The intensity ratios were calculated from the
areas under the peaks and no attempt was made to reduce
preferred orientations. The density, d, was measured by
Archimedes’ principle in water.
Fig. 1. XRD patterns of (a) Ti InC, (b) (Ti,Hf) InC, and (c) Hf InC.
2
2
2
Inset shows details of area around 2u5358, which clearly show that the
diffraction lines of the solid solution lie in between those of the end
members.
The heat capacities, c , were measured using a differen-
p

M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
175
Table 1
Summary of properties of M InC phases measured in this work. Also included are the lattice parameters measured in this work and those of Jeitschko et al.
2
[16]
Property
Ti InC
(Ti,Hf) InC
Hf InC
Comments
2
2
2
3
Measured density (Mg/m )
6.3
6.2
8.74
9.03
11.24
11.57
3
Theoretical density (Mg/m )
˚
Lattice parameters (A)
a
c
a
c
3.134
14.077
3.13
14.06
222.62
35.9
1.2310
0.20
0.0030
9.5310
|26.660.4
3.221
14.429
–
3.309
14.723
3.30
14.73
483.80
41.81
1.39310
0.19
0.0033
7.6310
26.561
This work
This work
Ref. [16]
Ref. [16]
–
Mol. wt. (g/mol)
Molar volume (g/cm )
Unit cell volume (m )
r0 (mV m)
a (K )21
TCE (K
ktot (W/m K)
353.21
40.6
1.3310
0.28
0.0025
8.65310
3
3
228
26
228
228
2
1
70–300 K
RT–1273 K
450–1350 K
26
26
)
1810.004T
Fig. 2. Backscattered SEM micrographs of (a) Ti InC, (b) Hf InC, (c) (Ti,Hf) InC, (d) Ti InC sample after 2-h hold in vacuum at 900 8C. Dark areas in
2
2
2
2
(
b) and (c) are HfC and HfO , respectively.
2

1
76
M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
between those of the end members. The XRD results for
the three compounds are summarized in Appendix A, and
again compared to the available data [16]. Based on these
results it is fair to assume that a complete solid solubility
occurs between Ti InC and Hf InC.
2
2
A typical backscattered SEM micrograph of the Ti InC
2
composition is shown in Fig. 2a. The sample is fully dense
and comprised of two phases; a gray matrix phase, Ti InC,
2
and a white discrete phase, which is In. The volume
fraction of the latter is |5 vol.%. According to EPMA of
the matrix phase, atomic ratios in % of Ti:In:C are
4
7.6(60.2):24.3(60.06):28.0(60.1). The numbers in brac-
kets denote the standard deviations. If one assumes the In
sites to be fully occupied, the resulting chemistry would be
Ti1.96InC1.15. The grains vary in size from 8 to 50 mm.
They are plate-like with aspect ratios of |3. The measured
3
density (6.3 Mg/m ) is in very good agreement with the
theoretical density calculated from the lattice parameters
(
Table 1).
Typical backscattered SEM micrographs of the Hf InC
Fig. 3. Temperature dependence of resistivity. The resistivity of the solid
solution is higher than the end members.
2
and (Ti,Hf) InC compositions are shown in Fig. 2b and c,
2
respectively. Here again the samples are almost fully dense
and predominantly single phase. In both cases, the mea-
sured densities are in excellent agreement with those
calculated from the lattice parameters (Table 1). The major
this system. The same phenomenon occurs in the Ti–Nb–
Al–C system where the resistivity of (Ti,Nb) AlC is
2
significantly higher than its end members, Ti AlC and
2
impurity phase in Hf InC is HfC (dark phase in Fig. 2b);
2
Nb AlC [12]. It is worth noting that a similar effect was
2
in (Ti,Hf) InC it is HfO (dark phase in Fig. 2c). Their
2
2
not observed in Ti AlC0.5N0.5 vis- a` -vis its end members,
2
volume fractions are quite low, however. The Hf:In:C ratio
Ti AlC and Ti AlN [13].
2
2
in
6.1(60.75):23.8(60.5):30.0(61.2).
Ti:Hf:In:C ratio in the solid
Hf InC
(dark
phase
in
Fig.
Similarly,
solution
2c)
is
the
is:
2
4
3
.3. Thermal properties
2
1.8(60.7):25.5(60.5):23.1(60.05):29.4(60.1).
Once
The functional dependence of the thermal strains on
temperature are shown in Fig. 4. Least squares fits of the
results—on both heating and cooling and over the entire
again assuming the In sublattice to be fully occupied, one
obtains: Hf1.94InC1.26 and (Ti0.47,Hf0.56)2InC1.26, for the
Hf-211 phase and solid solution, respectively.
3
.2. Electrical conductivity
Like all the MAX phases characterized to date, the
resistivities, r, of the ones studied here fall linearly with
decreasing temperature (Fig. 3). Hence r can be repre-
sented by:
r 5 r [1 1 a(T 2 300)] for T . 70 K
0
where r , a and T are, respectively, the resistivity at 300
0
K, the temperature coefficient of resistivity and the tem-
perature in Kelvin. The values of r and a obtained from a
0
least squares fit of the data are listed in Table 1. The most
conductive is Ti InC, followed by Hf InC, with the least
2
2
conductive being the solid solution. The residual resistivity
of the Hf InC is smaller than Ti InC, indicating that it may
2
2
be less defective; the difference is small, however.
Given that the residual resistivity of the solid solution is
significantly higher than the end members (Fig. 3) it is fair
to conclude that solid solution scattering is occurring in
Fig. 4. Bulk dilatometric thermal expansions. The curves are shifted to
the right by 2008 for the sake of clarity. Inset clearly shows that the
Ti InC expands at a higher rate than the Hf InC, with the solid solution
2
2
in between.

M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
177
i.e. the solid solution results in a destabilization of the
structure [13].
The effect of temperature on the heat capacities, c s, of
p
the In compounds is shown in Fig. 5. Also included for
comparison are the results for (Ti,Nb) AlC and Ti AlC.
2
2
The c s of Hf InC and the solid solution increase gradual-
p
2
ly with increasing temperatures starting at |500 K up to
100 K, after which the increases are more rapid. Since
1
such increases cannot be intrinsic to the samples, they are
most likely due to sample oxidation due to the presence of
residual oxygen in the Ar gas used during the measure-
ments. The two heavy dark lines through the data points
represent a least squares Debye model fit of the results.
Excluded from the fits are the data points represented by
solid triangles and squares (top right in Fig. 5). The Debye
fits were in turn fit to a third degree polynomial (not
shown), the coefficients of which are listed in Table 2 and
are only valid in the 400 to 1450 K range.
In the case of Ti InC (open diamonds in Fig. 5), c
2
p
Fig. 5. Temperature dependence of heat capacity for the In-containing
appears to first increase slightly, drop at |900 K, plateau
at a minimum around 1300 K, before increasing again.
Such complex behavior is not expected from a single phase
solid that does not go through phase transitions. The
increase at higher temperatures is most likely due to
phases measured here. Also included are the results for Ti AlC and
2
(
Ti,Nb) AlC [12]. The solid lines represent the least squares fits of the
2
data points to the Debye solid.
range measured—yield a mean thermal coefficient of
oxidation; the drop in c , on the other hand, must be
p
2
6
21
26
21
expansion, TCE, of 9.5310
K
and 8.65310
K
,
related to the loss of In from the sample (see below). Such
a loss would be endothermic and thus appear as a trough in
Fig. 5, as observed. Given that the results shown cannot be
used to determine c of Ti InC or its temperature depen-
for Ti InC and (Ti,Hf) InC, respectively. The fits, depicted
2
2
2
by dark dotted straight lines, have R values .0.99. For
reasons that are not entirely clear, Hf InC exhibits a
2
p
2
hysteresis upon cooling. Least squares fits of the heating
dence, the assumption was made that c of the latter was
p
2
6
21
and cooling portions yields 8.37310
K
and 6.83
identical to that of (Ti,Hf) InC. It is important to note that
2
2
6
21
26
21
1
0
K
, respectively, for an average of 7.6310
K
,
this problem was encountered only during the c measure-
p
which is plotted in Fig. 4 as a solid black line. It is
interesting to note that, the two other Hf-containing MAX
phases explored to date, viz. Hf SnC and Hf PbC [14],
also exhibit marked hysteresis upon heating and cooling.
We have previously shown a correlation between the
TCEs of the MAX phases and their near-stoichiometric
MX counterparts [14]. The results obtained here are in
ments because of the small samples we had to use. It is
hereby acknowledged that the heat capacity measurements
should be repeated with larger samples where the surface
to volume ratio is reduced.
2
2
The effect of temperature on the thermal conductivity,
ktot, is shown in Fig. 6. The thermal conductivities of the
end members are, given the error bars, almost identical at
|26.5 W/m K; those of the solid solution are lower. A
least squares fit of the solid solution results yields the
relationship listed in Table 1 (last row). Note that if the
phonon contribution, kph to the total thermal conductivity
is negligible and/or temperature-independent, mathemati-
cally dktot /dT will have the same sign as the intercept of r
with the y-axis. Since for the solid solution the intercept is
positive (Fig. 3), dktot /dT is also positive (Fig. 6).
agreement with this general principle. The TCE of Ti InC
2
is presumably higher than that of Hf InC because the TCE
2
2
6
21
of near-stoichiometric TiC (7.4310
K
[17]) is higher
2
6
21
than that of HfC (6.6310
K
[17]). It thus appears that
forming solid solutions on the M-sites results in TCE
changes that are reasonably well represented by the rule of
mixtures. The same is true for the Ti–Nb–Al–C system
[12]. This is in contrast to the Ti–Al–C–N system, where
the order of the TCEs is: Ti AlC0.5N0.5 .Ti AlC|Ti AlN,
In previous work, the Wiedemann–Franz Law (k 5
2
2
2
e
Table 2
Coefficients of third order polynomial of cp (5 A 1 BT 1 CT 1 DT ) that was fit to the Debye model. Values are in J/mol K
2
3
A
B
C
D
2
4
28
28
Hf InC
26.0
35.2
0.17
0.15
21.373102
21.2310
3.82310
3.35310
Only valid in the
400 to 1450 K range
2
4
(
Ti,Hf) InC
2
Ti InC
Same as (Ti,Hf) InC
2
2

1
78
M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
2
8
2
L T/r, where L 5 2.45 3 10
W V/K ) was used to
o
o
estimate the electronic contribution, k , to k [1,8–10,12].
e
tot
In some cases, the law was applicable without modi-
fications [8,9]; in others the nonsensical result that k . k
e
tot
was obtained, which by necessity implies that L has to be
o
2
8
2
,
2.45310 W V/K [10,12]. The same applies here; in
all cases k . k . From this it is concluded that in the
e
tot
compounds studied herein the heat is predominantly
2
8
carried by delocalized electrons and L , 2.45 3 10
W
o
2
V/K . This is not surprising since, with a few notable
exceptions, the majority of the heat in the MAX phases is
carried by electronic defects [1].
During the thermal diffusivity measurements, it was
noted that a thin silver mirror formed on the glass windows
capping the furnace tube. The film formed at higher
temperatures and, while occurring for all three compounds,
was most severe for the Ti InC samples. In some cases,
2
the film became so thick that it interfered with the signal
and rendered the measurements meaningless. Since this
behavior was only observed with In-containing MAX
Fig. 6. Temperature dependence of thermal conductivity. Typical error
bars are shown in figure.
Table A.1
˚
˚
Summary of XRD results for Hf InC. The calculated ds are based on c and a values of 14.723 A and 3.309 A, respectively
2
˚
˚
h k l
2u, measured
Observed d, (A)
Calculated d, (A)
I/Imax measured
I/Imax calculated [11]
0
0
1
1
0
1
1
2
2
2
1
0
0 2
0 4
0 0
0 3
0 6
0 6
1 0
0 1
0 3
0 6
1 8
0 12
12.054
24.202
31.176
36.295
36.616
48.805
55.487
65.591
68.261
76.554
77.013
77.775
7.3362
3.6744
2.8666
2.4721
2.4512
1.8645
1.6545
1.4221
1.3729
1.2435
1.2372
1.2269
7.361
3.68
15.6
19.2
25.3
100
66.2
21.2
15.5
11.3
37
5.7
1.4
23.2
100
–
15.3
20.3
0.64
27.5
13.1
0.08
9.1
2.8656
2.4753
2.4538
1.864
1.6545
1.4266
1.3759
1.2376
1.2309
1.2269
8.6
8.3
9.7
Table A.2
Summary of XRD results for Ti InC. The calculated ds are based on c and a values of 14.077 A and 3.31344 A, respectively
˚
˚
2
˚
˚
h k l
2u, measured
Observed d, (A)
Calculated d, (A)
I/Imax measured
I/Imax calculated [11]
0
0
1
1
1
1
1
1
1
1
1
1
0
0 2
0 4
0 0
0 1
0 2
0 3
0 5
0 7
1 0
1 2
1 4
1 6
0 12
12.546
25.276
32.955
33.602
35.423
38.3
46.441
56.946
58.879
60.411
65.213
72.491
82.088
7.0410
3.5207
2.7158
2.6650
2.5320
2.3481
1.9538
1.6158
1.5672
1.5311
1.4295
1.3029
1.1731
7.0386
3.5193
2.7145
2.6654
2.5326
2.3496
1.9541
1.6158
1.5672
1.5297
1.4316
1.3032
1.1731
14.4
14.5
19
6.7
3.5
100
3.8
3
8.8
1
1.9
23.9
6
20.3
11.9
20.3
18
8.4
100
6.9
6.1
19.6
3.4
4.6
17.7

M.W. Barsoum et al. / Journal of Alloys and Compounds 340 (2002) 173–179
179
Table A.3
Summary of XRD results for (Ti,Hf) InC. The calculated ds are based on c and a values of 14.429 A and 3.221 A, respectively
˚
˚
2
˚
˚
h k l
2u, measured
Observed d, (A)
Calculated d, (A)
I/Imax measured
0
1
1
1
1
0
0
0
0 4
0 0
0 3
0 6
1 0
2 0
2 3
0 12
24.651
32.053
37.268
50.033
57.155
67.344
70.263
79.678
3.60857
2.79012
2.41081
1.82157
1.61034
1.38933
1.33859
1.2024
3.6072
2.7892
2.4128
1.8213
1.61034
1.3946
1.3394
1.2024
8.9
18.2
100
13.8
16.6
17
23.8
4.4
phases, the film was assumed to be In. To test this
Appendix A
hypothesis, a Ti InC sample was placed in vacuum and
2
held at 900 8C for |2 h, after which its surface was
characterized. The XRD patterns (not shown) clearly
showed the emergence of peaks corresponding to TiCx.
SEM of the same surface (Fig. 2d) indicated that a
complete restructuring of the surface occurs. When taken
together with a loss in weight, it is clear that under vacuum
and at temperatures around |1000 K, the In-containing
samples lost In most probably according to:
Tables A.1–A.3 show summaries of the XRD results.
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1
[
(
M InC 5 MC 1 In (vap.)
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x
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p
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2
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[
[
[
[
[
[
[
[
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Acknowledgements
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82.
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We would like to thank Prof. F. Sommer (MPI Metal-
lforschung, Stuttgart, Germany), for carrying out the heat
capacity measurements and Mr. A. Ganguly for the lattice
parameter measurements. This work was partially funded
by the Division of Materials Research of the National
Science Foundation (DMR, 0072067). The support of Prof.
M. Ruehle and the Humboldt and Max Planck Foundations
to one of the authors (MB) during his sabbatical leave in
Germany is also gratefully acknowledged.
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