research paper 		

セラミックス基盤工学研究センター年報 (2006). Vol. 6, 12 -18

電子密度分布解析用高温単結晶 X 線回折システムの開発
石澤伸夫 †・近藤早 †・日比野寿 †・五十嵐眞悦 ‡・中村光雄 ¶・佐保良二 ¶†名古屋工業大学セラミックス基盤工学研究センター‡

ブルカー・エイエックスエス ( 株 )¶〒 507-0071 岐阜県多治見市旭ヶ丘 10-6-29〒 221-0022 神奈川県横浜市神奈川区守屋町 3-9-A

日本サーマルエンジニアリング ( 株 ) 〒 229-1132 神奈川県相模原市橋本台 1-6-2

Development of High-Temperature Single-Crystal X-ray Diffraction
System for Electron Density Distribution Analyses
N. Ishizawa†, S. Kondo†, H. Hibino†, S. Igarashi‡, M. Nakamura¶ and R. Saho¶†

Ceramics Research Laboratory, Nagoya Institute of Technology, 10-6-29, Asahigaoka, Tajimi 507-0071‡¶

Bruker AXS K. K., 3-9-A, Moriya-cho, Kanagawa-ku, Yokohama 221-0022

Japan Thermal Engineering Co., Ltd., 1-6-2, Hashimotodai Sagamihara 229-1132

A new high-temperature diffraction system has been developed to collect accurate and precise single-crystal diffraction data at highresolution levels. The high-temperature apparatus is composed of two devices of a hot nitrogen gas blower and its duct which are locatedvery close to the specimen so as to avoid heat dissipation to the other parts. The apparatus is attached to the CCD diffractometer toenable fast data collection at high temperatures up to over 1000 ºC with a stability of less than 1 ºC. The apparatus places no geometricalrestriction to the diffractometer, allowing measurements up to 120º in 2θ . High temperature diffraction data were collected for the α-Al2O3
single crystal at 300, 600 and 900 ºC within 3 hours for each measurements. The merge R factors were less than 0.019 and the final
agreement factors between Fo and Fc were less than 0.031 in the range 1º < 2θ < 92º. The Al atom was found to be gradually displacedwith increasing temperature so that the Al-Al repulsion force across a pair of face-sharing octahedra can relax. The system will contribute to
the electron density studies of functionally important inorganic materials at elevated temperatures.
[Received February 5, 2007; Accepted March 9, 2007]

1. Introduction
There has been an increasing demand to determine
accurate electron density distribution and atom structuresof crystalline materials at high temperatures in order tounderstand their physical properties. Recent developmentof area detectors and its integration with the single crystal diffractometer is achieving a marvelous success in
obtaining data in much shorter time than the conventional point-detector diffractometer system. This is a great
advantage in high-temperature diffraction experiments
where the thermal degradation of crystals can often occur.
In this paper we report a development of new hightemperature single-crystal diffraction system which cancontrol specimen temperatures in the range between
room temperature and slightly over 1000 ºC. The heating apparatus is originally designed for the χ-fixed CCD— 12 —

diffractometer (Bruker Smart Apex II). However, the apparatus is essentially independent of the diffractometer
geometry and can be applicable to a wide range of diffractometers with both area- and point-type detectors.
The present paper first describe the high temperatureapparatus and secondly demonstrate an example of thefast measurement of diffraction data at high temperaturesusing α-Al2O3 (corundum) single crystal.

2. Basic concepts
On designing a high-temperature single-crystal diffraction system, there are many important points to beconsidered. As mentioned in the previous section, thefast measurement to avoid heat damage is essential. The
adoption of area detector is most advantageous in thispoint.
The inorganic crystals have moderate diffracted in-電子密度分布解析用高温単結晶 X 線回折システムの開発

Fig. 1. Cross section of the hot gas blower.

Fig. 2. A view of the high-temperature apparatus attachedto the CCD diffractometer Smart Apex II. A: Chi cradle withgoniometer head (Huber model 1004). B: CCD detector. C:
total-reflection capillary collimator tube. D: microscope. E:
Hot gas blower. F: Gas duct. G: xyz stage for positioning
the gas duct. H: xyz stage for positioning the crystal heater.
J: Polyimide film (Kapton film, DuPont) to protect detector
window. K: Two-theta arm L: Omega stage

tensities even at high 2θ angles owing to the small thermal vibration of constituent atoms compared with the organic crystals. Data should be measured up to the upper
limit of 2θ mechanically available for the diffractometerin order to carry out the electron density studies at highresolution levels. Merging high-angle frame data with
low-angle ones used to be difficult in the past but now the
problem has been almost solved in latest area-diffractometers.
Reconstruction of precession images from hundredsof frame data measured by the area detector is also essential to see what is going on in the crystal at high temperatures. This is especially the case when the crystal
undergoes the phase transition or thermal decomposition.
Because of the reasons above, the CCD diffractometer(Smart Apex II, Bruker AXS) was chosen as a base system.
The CCD detector is usually placed relatively close
to the crystal to increase effective detection area in reciprocal space. This is especially the case for inorganic
crystals with relatively small unit cells. The default distance is approximately 60 mm from the crystal in our
diffractometer. The collimator and beamstop are also
placed very close to the crystal to prevent air scattering.
No large space in the CCD diffractometer is available
for the heating apparatus compared with point detectors
which usually has a crystal–detector distance of about
200 mm. Therefore the heat shield problem is of vital importance in designing the heating apparatus. In addition
any geometrical restriction for the ω and j move should— 13 —

石澤伸夫，近藤早，日比野寿，五十嵐眞悦，中村光雄，佐保良二

1000

Ts (ºC)

800
600
400
200
Fig. 3. K-type fine gauge thermocouple at the crystal

0

position heated at 1000 ºC. The fine scale of the microscope

200

400

600

800

1000

Th (ºC)is 20 μ m. The pink color reflects the bright Pt wire heater inthe blower. See also Fig. 6 which shows a crystal instead ofFig. 4. Comparison between the temperatures of the heater

thermocouple with the same scale.

(Th) and the crystal position (Ts) .

3. The high-temperature apparatus
The cross section of the hot-gas blower is illustrated
in Fig. 1. A platinum heater encapsulated in a silica glass
tube heats the nitrogen gas (7 l/min ) passing through the
tube. The heater assembly is heat-shielded by multiple
concentric walls for vacuum insulation and water-cooling. The heated gas comes out from the end opening of 5
— 14 —

850

Ts (°C)be avoided.
After various thoughts and trials, it was decided to
employ a technique to elevate sample temperature byplacing it in a hot gas stream. This technique can make aneffective use of two spaces available for the χ-fixed CCD
diffractometer, that is, a large space on top of the crystal
and a small one just below it. The high-temperature attachment to the diffractometer is composed of two devices, a hot-gas blower and a gas duct. These devices areclosely placed in the opposite sides of the crystal along
the vertical line. A tight combination of the two devices
in short distance enables a formation of a small columnar hot zone so that the heat diffusion to the other partsaround the crystal can be minimized.
The diffraction intensities become weak due to thermal smearing at high temperatures. The incident X-rays
should be intense enough to cope with the decay of diffracted intensities. The capillary optics based on the concept of total X-ray reflection (He & Preckwinkel, 2002)
has been employed for the collimator in order to improvestatistics of diffracted intensities.

800

750
0

2

4

6
8
z-scale (mm)1012Fig. 5. Changes of temperature at the crystal position (Ts) as afunction of nozzle position (Th=800 ºC).

mm in diameter of the silica glass tube. The sheath gas issupplied through the space between the silica glass tube
and vacuum insulation tube. A constant flow of sheathgas (10 l/min) contributes to the formation of stable coolgas layer wrapping the hot gas stream and protects theequipment around the specimen; detector, collimator,
beamstop, goniometer-head, etc.
The heat and sheath gases are supplied from a laboratory-type nitrogen gas generator (JAN3-08-MS, Japan
Thermal Engineering Co., Ltd.), using the PSA (Pressure-Swing-Adsorption) technology. The temperature of
the hot gas is measured by a Pt/Pt13%Rh thermocouple
placed near the top (gas exit) of the blower nozzle, and電子密度分布解析用高温単結晶 X 線回折システムの開発

Table 1. Comparison of diffracted intensities of ylid between the total-reflection capillary collimatorand the single-pinhole conventional collimator with 0.5 mm openings (Mo Kα tube).
h
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

k
-1
-2
-2
-3
-3
4
-4
-4
5
-5
-5
6
-6
-6
7
-7
-7

capillary collimator
l
I
-5
30662
-7
2031
-8
1294
-9
3410
-10
30403
-3
25374
-10
66
-11
4587
-3
1919
-11
8104
-12
31952
-3
19902
-12
5818
-13
1942
-3
308
-12
2229
-13
3304

σ (I)
218
69
59
106
323
221
28
139
69
195
397
237
181
112
38
123
150

h
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

controlled by a PID (Proportional-Integral-Derivative)
controller. The exhaust gas is immediately evacuatedthrough the gas duct composed of flexible bellows-typeconcentric double tube made of stainless steel. The exhaust gas in the inner bellows tube is cooled by waterrunning between the inner and outer tubes. The detector
face is protected by the Polyimide (Kapton) film of 25
μm thick in case of unexpected scatter or evaporation ofsample, ceramic adhesive, glasses, and /or heater materials.

4. Temperature calibration
The present apparatus can raise and hold the specimen temperature from room temperature to over 1000
ºC within the stability less than 0.5 ºC for long duration.
The specimen temperature was examined by various
methods. First the difference between the temperature(Th) for power control and the temperature (Ts) at the
specimen position was examined. The K-type fine sheet
gauge thermocouple (KFC-50-200-100, Anbe SMT Co.)
was placed at the crystal position as shown in Fig. 3. The
junction of the thermocouple is 50 μm in size and 20 μm
in thickness. The relation between Th and Ts is plotted inFig. 4. The plot points came close to the straight line witha unit slope, though Ts indicated slightly higher temperatures than Th in general. This tendency became distinct
with increasing temperature, especially above 800 ºC.
Sample temperature was also calibrated by measur-conventional collimator
k
l
I
-1
-5
15917
-2
-7
1103
-2
-8
665
-3
-9
1806
-3
-10
15393
4
-3
12927
-4
-10
25
-4
-11
2481
5
-3
953
-5
-11
4194
-5
-12
16624
6
-3
10189
-6
-12
3108
-6
-13
884
7
-3
180
-7
-12
1165
-7
-13
1635

σ (I)

154
51
43
77
230
157
19
103
49
141
285
170
132
76
31
89
105

gain
1.926
1.842
1.944
1.889
1.975
1.963
2.670
1.849
2.014
1.932
1.922
1.953
1.872
2.197
1.706
1.913
2.022

ing melting points of the metal crystals, Sn (mp=231.9ºC), Zn (mp=419.5 ºC), and Ag (mp=960.8 ºC). The melting of Pb and Ag crystals on heating was easily observed
through the computer display connected to microscopewith video output. The heater temperature (Th) indicated
236 and 968 ºC on melting, respectively. The departureof Th from the true temperature was thus estimated to beapproximately 4 ºC at 232 ºC and 7 ºC at 961 ºC. The
Zn crystal was easily oxidized and covered by a toughZnO skin, making difficult to observe the melting phenomenon through the microscope.
The effect of nozzle position on the temperature of
specimen was examined. Changes of Ts at Th = 800 ºC
is given in Fig. 5. It should be noted that the horizontal
axis of the figure reads the z-scale of the xyz stage of theheating nozzle directly. The crystal centre is displaced
approximately 3 mm along z from the z = 0 position.
Therefore the true distance between the crystal and the
top of the heat nozzle can be obtained by adding 3 to thez-scale in mm. A significant temperature gradient along z
existed. The temperature of the gas stream is estimated to
be almost the same within the columnar hot zone. ThereTable 2. Data collection strategy at high temperatures. S is thetotal sweep angle about the scan axis.
Scan typejωωω

— 15 —2θ (º)
-67.5
-47.5
-27.5
57.5

ω (º)
-122.50-88.54-107.97-119.63j (º)-118.28325.00200.00270.00

t (s)
15.0
10.0
10.0
10.0

w (º) S (º)
0.5 127.5
0.5
34.0
0.5
56.0
0.5 118.5

石澤伸夫，近藤早，日比野寿，五十嵐眞悦，中村光雄，佐保良二

Table 3. Results of refinement I. Nref1 and Nref2 are the numbers of measured reflections and crystallographically independent ones
with I > 2σ (I), respectively. Rint is the merge R factor, and R is the reliability factor for the Nref2 reflections after the leastsquares refinement. NR stands for 'not reported'. Data at 1900 ºC are imported from reference (Ishizawa et al., 1980).
T(ºC)

Nref1

2θ max

Rint

Nref2

R

a

c

Al z

Ox

24
300
600
900
1900

1581
535
537
529
NR

120
92
92
92
60

0.01520.01880.01660.0122
NR

406
202
203
205
NR

0.01900.03040.02450.02270.03804.7617(1)4.7701(1)4.7805(1)4.7936(1)4.844(2)12.9990(2)13.0246(4)13.0561(3)13.0955(3)13.27(2)0.352156(17)0.35226(4)0.35242(3)0.35260(4)0.3533(2)0.69364(7)0.69355(19)0.69357(15)0.69342(18)0.6936(1)Table 4. Results of refinement II. Data at 1900 ºC are imported fromreference (Ishizawa et al., 1980). NR stands for 'not reported'.
T(ºC)
23
300
600
900
1900

Al U110.00305(7)0.0071(2)0.00832(19)0.0108(2)0.0299(22)Al U330.00370(8)0.0059(2)0.00866(19)0.0122(2)0.0255(22)Al U120.00152(3)0.00356(12)0.00416(10)0.00540(11)NR

Al Uiso0.00327(6)0.0067(2)0.00843(16)0.01126(19)0.0285
Fig. 6. Spherically-ground corundum crystal heated at 900 ºC.
The fine scale of the microscope is 20 μ m.

Table 5. Results of refinement III. Data at 1900 ºC are imported from reference (Ishizawa et al., 1980). NR stands for 'not reported'.
T(ºC)
23
300
600
900
1900

O U11
0.00358(8)0.0078(3)0.0087(2)0.0108(3)0.0282(28)O U220.00380(10)0.0081(3)0.0089(3)0.0117(3)0.0290(37)O U33
0.00430(10)0.0065(3)0.0095(2)0.0132(3)0.0275(33)O U120.00190(5)0.00405(17)0.00446(14)0.00586(17)
NR

O U13
0.00035(3)0.00064(10)0.00091(8)0.00114(10)
NR

O U23
0.00070(7)0.0013(2)0.00181(15)0.0023(2)0.0046(24)O Uiso0.00387(6)0.0074(2)0.00902(17)0.0118(2)0.0281

13.3
4.84
13.2
c (Å)

a (Å)

4.82

4.80

13.1

4.78
13.0
4.76
0

500

1000

1500

2000

0

500

1000
T(ºC)

1500

2000

T(ºC)
Fig. 7. Temperature dependence of the cell parameter a ofFig. 8. Temperature dependence of the cell parameter c ofcorundum. Data at 1900 ºC are imported from reference

corundum. Data at 1900 ºC are imported from reference(Ishizawa et al., 1980).

(Ishizawa et al., 1980).

— 16 —

電子密度分布解析用高温単結晶 X 線回折システムの開発

obtained from the standard crystal (ylid, C11H10O2S) is
given in Table 1. The average intensity gain was 2.02(3)for observed 171 reflections. It was confirmed from various room temperature preliminary experiments that theaccuracy of the high angle data improved significantly by
the use of capillary optics.

Al z coordinate

0.35320.3528

6. Corundum structure at high temperatures

0.35240.3520
0

500

1000

1500

2000

T(ºC)
Fig. 9. Temperature dependence of the z parameter of Al
in corundum. Data at 1900 ºC are imported from reference(Ishizawa et al., 1980).

Uiso (Å2)

0.03000.02000.0100

0

500

1000

1500

2000

T(ºC)
Fig. 10. Temperature dependence of isotropic atomic
displacement parameters for Al (square) and O (triangle)of corundum. Data at 1900 ºC are imported from reference(Ishizawa et al., 1980).

fore, the observed gradient is supposedly caused by theradiation directly emitted from the platinum heater. It is
important to confirm the nozzle position being set at thesame position for each experiments.

5. Capillary optics of the collimator
The use of the total-reflection capillary collimator(RLR-173-0.5Cu(Mo), Bruker AXS) gave approximately
twice as strong diffracted intensities compared with thesingle 0.5 Ø pinhole collimator. The integrated intensities
and their estimated uncertainties of several reflections

The α-Al2O3 (corundum) single crystal was groundinto a sphere of approximately 70 μm in radius by theBond method. The crystal was mounted on a tapered
silica glass capillary by the ceramic adhesive. The photograph of the crystal heated at 900 ºC is shown in Fig. 6.
Data were collected at 300, 600 and 900 ºC on heating, and 24 ºC after cooling. The strategy of data collection at high temperatures are optimized so that the total
measurement time becomes approximately 3 hours, data
completeness is close to 100% within 2θ < 80º, and redundancy of equivalent reflections is close to 3. The
calculated strategy is given in Table 2.

The results of refinements are tabulated in Tables 3,
4 and 5 in the hexagonal setting. Changes of the a andc cell dimensions of α-Al2O3 with temperature areshown in Figs. 7 and 8, respectively. They increases
as a function of temperature, and are smoothly extrapolated to data at 1900 ºC reported by Ishizawa etal., (1980). The unit cell structure of α-Al2O3 has two
positional variables; z for Al and x for O. The fractional coordinate of Al z increased as a function oftemperature as shown in Fig. 9. It was smoothly extrapolated to the value at 1900 ºC. On the other hand
there was no significant systematic change in the O xparameter.
The temperature changes of the isotropic atomic displacement parameters (Uiso) of Al and O is shown in Fig.
10. A small convex at around 300 ºC was observed forboth Al and O atoms. We think that this convex is simply an artefact due to low quality data of 300 ºC. Actually a large amount of the ceramic adhesive was observedin the virgin crystal mounted on the silica glass capillary. The precession images constructed from the frame
data at 300 ºC showed a presence of strong powder rings
due to the adhesive. The excessive adhesive evaporated
completely after the measurement at 300 ºC. The powder
rings became quite faint after that, resulting in a successful retrieval of integrated intensities from the 600, 900
and 24 ºC (on cooling) frame data. It is noted that as
small amount of ceramic adhesive as possible should be— 17 —

石澤伸夫，近藤早，日比野寿，五十嵐眞悦，中村光雄，佐保良二

used for the precise and accurate data collection.

The α-Al2O3 structure contains a pair of AlO6 octahedra sharing a face. The Al-Al distance along thec axis through the shared face is the shortest among
all Al-Al distances. The increase of Al z fractional
coordinate can be interpreted as a structural relaxation to accommodate the elongation of the shortest
Al-Al distance at high temperatures, working in cooperation with the expansion of the unit cell. It is suggested that the electrostatic repulsion forces between
higher valence atoms increase at high temperatures.

7. Conclusion
A new high-temperature single-crystal diffraction system has been developed. The high-temperature apparatus
is composed of the gas blower and the gas duct which arelocated very closely to the sample to avoid heat diffusion.
The apparatus is attached to the CCD diffractometer toenable fast data collection at high temperatures. The
system also includes nitrogen gas generator from air andthe power supply for the PID controlled platinum heater— 18 —and various safeguards. The temperature can be raised
from room temperature to over 1000 ºC. Single-crystal
diffraction data were successfully collected for α-Al2O3
at 300, 600 and 900 ºC within only 3 hours for each. The
results of refinements provided precious structural information about the systematic shift of Al position at hightemperatures. The system will contribute for the precise
and accurate electron density studies of functionally important inorganic materials at elevated temperatures.

Acknowledgements
This study was supported by grants-in-aid for Scientific Research No. 18206071 from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

References
B. B. He and U. Preckwinkel (2002). Advances in X-ray Analysis,
Volume 45, 332-337.
N. Ishizawa, T. Miyata, I. Minato, F. Marumo and S. Iwai
(1980). Acta Cryst. B36, 228-230.