Photon Factory Activity Report 2017 #35 (2018)

BL-15A1/ 2015S2-002, 2016S2-001

Development of XAFS/XRD simultaneous measurement technique
at high temperatures

Ken’ichi Kimijima1, Toshiki Watanabe1, Yasuo Takeichi1, Yasuhiro Niwa1, Masao Kimura1,*1
Photon Factory, 1-1 Oho, Tsukuba, 305-0801, Japan
1 Introduction
In order to increase the energy efficiency of gas turbine
engines used in aircrafts, it is necessary to operate at atemperature higher than the current temperature. Evaluate
methods of the properties of structural materials used atultrahigh temperatures such as gas turbine blades ofengines are required, and it is essential to have atechnique to accurately measure changes in structure andchemical state proceeding under these conditions. Thus,in situ measurement technique at ultra-high temperature isrequired. As various type of reactions, such as diffusionof main component, phase transition, and precipitation ofminor phases, are expected, the combination ofcomplemental analytical techniques is inevitable.
Considering these requirements, we are developing atechnology to measure simultaneously a short-range
structure obtained by XAFS and a long-range structure
obtained by diffraction measurement at ultra-hightemperature up to 1500 °C. We have developed aprototype in situ furnace to investigate elemental
technologies for spectroscopic measurements atextremely high temperatures, and have been accumulating
XAFS measurement techniques at high temperatures [1].
Here we report the development of the in situ the furnace
for spectroscopic / diffraction measurement and typicalresults of XAFS / XRD measurements.
2 Experiment
The XAFS / XRD simultaneous measurement furnace
was developed based on an infrared furnace (gold imagefurnace) which is not susceptible to properties of material
such as a thermal conductivity of the sample as a heatingmethod. In order to simulate the operating condition of anaircraft engine, we aimed at measurement at 1500 °C for
regular use. The heating area in the cell is about 10 × 10mm at the sample position, which is sufficiently larger
than the X-ray beam irradiation area. Figure 1 shows
photographs of the novel ultra-high temperature
XAFS/XRD furnace under development, which isinstalled at the beam line of synchrotron facility. For
heating experiments, a sintered plate of Yb2Si2O7 (8 × 8mm, t = 0.5 mm) was used as a sample. Measurements ofYb LIII absorption edge (8944 eV) and diffraction (8046eV) were carried out at KEK PF BL-15A1, at whichsemi-micro beam (about 20 μm) can be utilized. XAFS
was measured by detecting the fluorescence from thesample with a silicon drift detector (SDD) or Lytle
detector from the direction of 90° with respect to the Xray optical axis. For the XRD measurement, the required
angular range was measured in multiple steps using
PILATUS 100k installed in a goniometer. The camera
length was 200 mm. The spot diameter of the irradiated

X-ray beam on the sample was estimated to be about 0.2(vertical) × 0.1 (horizontal) mm. This is because the beam
spread in the lateral direction is deviated from the focal
position, and the beam spread in the longitudinal direction
is caused by tilting the specimen. Temperature rise wascarried out under continuous gas (air, N2) flow.

Fig. 1. Set-up of the measurement system at PF BL-15A1.
3 Results and Discussion
As a result of the heating test, it reached 1500 °C at aheating rate of 500 °C min-1. The stability is ± 3.9 °C
when kept at 1500 °C for 30 min, which is considered tobe sufficient heating performance for spectrum
measurement at ultra-high temperature. Figure 2.a shows
XAFS oscillations measured with various temperatures.
From the XANES spectra of Yb2Si2O7 around Yb LIII
edge, no energy shift of spectrum was observed before
and after heating, showing that the valence of Yb does notchange. The radial structure functions which are obtainedby Fourier transform of EXAFS oscillation with a rangeof k = 1-12 × 10 nm-1. Because EXAFS oscillations
changed reversibly during heating cycles, it means that noirreversible structural change is caused during heatingcycles. Since the oscillation cycle has not changed andonly the decrease in oscillation intensity, which isconsidered to be due to the increase of Debye-Waller
factor accompanying temperature increase, is observed, itsuggests that the local structure around Yb does notchange.
Figure 2.b shows the diffraction patterns obtained,
where each image is a part of Debye-Scherrer ringcovering the diffraction angles of 2θ = 4 to 46°. Becauseof the small beam size, the XRD measurements are
sensitive to change of grain growth, which is expected athigh temperatures. However, the distinct change was notobserved, showing that no severe grain growth wasPhoton Factory Activity Report 2017 #35 (2018)

observed during heating under the conditions ofexperiments.
From the above, it was shown that simultaneous
observation of XAFS and XRD at the same sample
position can be measured at high temperature, and that itprovide crucial information of change of structures bothin short- and long- range ordering.
Now we are improving the way to hold the specimen athigh temperatures and control the temperature more
precisely.

(a)
R.T after
heatingk3χ(k)

1500 ℃
1100 ℃
700 ℃
R.T.

02

4

6810k / 10 nm-1(b)Fig. 2 (a) XAFS oscillation (Yb LIII) and (b) diffraction
image of Yb2Si2O7 sintered plate measured at various
temperatures (R. T. ~ 1500 °C).
Acknowledgement
This work was supported by SM4I, SIP of JST.
Experiments using synchrotron radiation were performed
with the approval of the Photon Factory at IMSS, KEK
Program Advisory Committee (Proposal Nos. 2015S2002 and 2016S2-001).
References[1] K. Kimijima, Y. Takeichi, Y. Niwa, K. Takahashi, andM. Kimura, 2nd SIP-IMASM, 57 (2016).
* masao.kimura@kek.jp