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Structural degradation of tungsten sandwiched in hafnia layers determined by in-situ XRD up to 1520 °C
Citation Link: https://doi.org/10.15480/882.3485
Publikationstyp
Journal Article
Date Issued
2021-02-08
Sprache
English
TORE-DOI
TORE-URI
Journal
Volume
11
Issue
1
Article Number
3330
Citation
Scientific Reports 11 (1): 3330 (2021-02-08)
Publisher DOI
Scopus ID
PubMed ID
33558611
Publisher
Macmillan Publishers Limited, part of Springer Nature
The high-temperature stability of thermal emitters is one of the critical properties of thermophotovoltaic (TPV) systems to obtain high radiative power and conversion efficiencies. W and HfO are ideal due to their high melting points and low vapor pressures. At high temperatures and given vacuum conditions, W is prone to oxidation resulting in instantaneous sublimation of volatile W oxides. Herein, we present a detailed in-situ XRD analysis of the morphological changes of a 3-layer-system: HfO /W/HfO layers, in a high-temperature environment, up to 1520 °C. These samples were annealed between 300 °C and 1520 °C for 6 h, 20 h, and 40 h at a vacuum pressure below 3 × 10 mbar using an in-situ high-temperature X-ray diffractometer, which allows investigation of crucial alterations in HfO and W layers. HfO exhibits polymorphic behavior, phase transformations and anisotropy of thermal expansion leads to formation of voids above 800 °C. These voids serve as transport channels for the residual O present in the annealing chamber to access W, react with it and form volatile tungsten oxides. An activation energy of 1.2 eV is calculated. This study clarifies the limits for the operation of W-HfO spectrally selective emitters for TPV in high-temperature applications. 2 2 2 2 2 2 2 –6
DDC Class
600: Technik
620: Ingenieurwissenschaften
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