A high-temperature<i>in situ</i>cell with a large solid angle for fluorescence X-ray absorption fine structure measurement

Murata, Naoyoshi; Kobayashi, Makoto; Okada, Yukari; Suzuki, Toshiharu; Nitani, Hiroaki; Niwa, Yasumasa; Abe, Hitoshi; Wada, Takahiro; Mukai, Sonoyo; Uehara, Hiroki; Ariga, Hiroko; Takakusagi, Satoru; Asakura, Kiyotaka

doi:10.1063/1.4914459

Cited by 5 publications

(8 citation statements)

References 54 publications

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“…Murata and co-workers have developed a cell suited for moderate vacuum conditions on the one hand, while employing large X-ray windows for fluorescence mode EXAFS experiments or X-ray diffraction (Murata et al, 2015). Here, however, the temperature is limited to about 600 C, due to the absence of cooled windows.…”

Section: Introductionmentioning

confidence: 99%

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

Klaes

Rothweiler

Bornmann

et al. 2021

J Synchrotron Radiat

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Niobium metal foils were heat-treated at 900°C under different conditions and in situ investigated with time-resolved X-ray absorption fine-structure (EXAFS and XANES) measurements. The present study aims to mimic the conditions usually applied for heat treatments of Nb materials used for superconducting radiofrequency cavities, in order to better understand the evolving processes during vacuum annealing as well as for heat treatments in controlled dilute gases. Annealing in vacuum in a commercially available cell showed a substantial amount of oxidation, so that a designated new cell was designed and realized, allowing treatments under clean high-vacuum conditions as well as under well controllable gas atmospheres. The experiments performed under vacuum demonstrated that the original structure of the Nb foils is preserved, while a detailed evaluation of the X-ray absorption fine-structure data acquired during treatments in dilute air atmospheres (10−5 mbar to 10−3 mbar) revealed a linear oxidation with the time of the treatment, and an oxidation rate proportional to the oxygen (air) pressure. The structure of the oxide appears to be very similar to that of polycrystalline NbO. The cell also permits controlled exposures to other reactive gases at elevated temperatures; here the Nb foils were exposed to dilute nitrogen atmospheres after a pre-conditioning of the studied Nb material for one hour under high-vacuum conditions, in order to imitate typical conditions used for nitrogen doping of cavity materials. Clear structural changes induced by the N2 exposure were found; however, no evidence for the formation of niobium nitride could be derived from the EXAFS and XANES experiments. The presented results establish the feasibility to study the structural changes of the Nb materials in situ during heat treatments in reactive gases with temporal resolution, which are important to better understand the underlaying mechanisms and the dynamics of phase formation during those heat treatments in more detail.

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Section: Introductionmentioning

confidence: 99%

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

Klaes

Rothweiler

Bornmann

et al. 2021

J Synchrotron Radiat

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“…We applied in situ fluorescence EXAFS and developed a new in situ reaction cell. 29 We obtained a good S/N ratio for the in situ Pt L 3 -edge EXAFS signal under reducing gas at high temperatures using the in situ cell that allows us to detect the fluorescence signal with a large half-cone angle (56°). We can carry out data analysis using difference spectra to elucidate minute changes in EXAFS oscillations during reactions.…”

Section: Introductionmentioning

confidence: 89%

“…32 The in situ XAFS was measured in fluorescence mode using an in situ fluorescence XAFS measurement cell described elsewhere. 29 XAFS spectra were analyzed with REX2000 (Ver. 2.5, RIGAKU).…”

Section: Sample Preparationmentioning

confidence: 99%

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Structure of Atomically Dispersed Pt in a SnO₂ Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis

Murata

Suzuki

Lin

et al. 2022

ACS Appl. Mater. Interfaces

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A battery-driven micro electromechanical system (MEMS) gas sensor has been developed for household safety when using natural gas. The heart of the MEMS gas sensor is a 7.5 at % Pt−SnO 2 thin film catalyst deposited on the SnO 2 sensor layer. The catalyst enhances the sensitivity to methane, though its structure under working conditions is unclear. In this study, in situ XAFS was applied to a 7.5 at % Pt−SnO 2 catalyst layer deposited on a Si substrate, and we demonstrated that atomically dispersed Pt maintains its lattice position in SnO 2 with a small loss of surrounding lattice oxygen in the presence of 1% CH 4 and a more reducing gas of 1% H 2 at the reaction temperature (703 K), i.e., no Pt aggregation is observed. The lost oxygen is easily recovered by re-oxidation by air. This work has revealed that the atomically dispersed Pt in the SnO 2 lattice is the active structure and it is stable even under reaction conditions, which guarantees a long lifetime for the gas sensor.

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“…They characterized the structure under in situ conditions, where the sample was heated to high temperature in a flow of hydrogen or methane gas, using an X-ray absorption fine structure (XAFS). 7,8 They found that their model sensor comprised atomically dispersed Pt in SnO 2 , which was the active species that enhanced the sensor activity, and that PdO was present in the Pd/Al 2 O 3 catalyst overlayer and it increased the methane sensitivity of the sensor.…”

Section: Introductionmentioning

confidence: 99%

Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS

Wada

Murata

Uehara

et al. 2016

Phys. Chem. Chem. Phys.

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Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by μ-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a freshly prepared sensor, all Pd species were in the PdO form; in a heavily deteriorated sensor, Pd/Al2O3 in the external region changed to metallic Pd particles, while the PdO structure in the inner region near the heater remained unchanged. The Pd species distribution was in agreement with the simulated thermal distribution. Temperature control was crucial to maintain the high performance of the gas sensor. The improved sensor allows homogeneous heating and has a lifetime of more than 5 years.

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A high-temperaturein situcell with a large solid angle for fluorescence X-ray absorption fine structure measurement

Cited by 5 publications

References 54 publications

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

Structure of Atomically Dispersed Pt in a SnO₂ Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis

Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS

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A high-temperaturein situcell with a large solid angle for fluorescence X-ray absorption fine structure measurement

Cited by 5 publications

References 54 publications

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

Structure of Atomically Dispersed Pt in a SnO2 Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis

Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS

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Product

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Structure of Atomically Dispersed Pt in a SnO₂ Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis