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Publisher DOI: 10.1038/s41598-021-82821-0
Title: Structural degradation of tungsten sandwiched in hafnia layers determined by in-situ XRD up to 1520 °C
Language: English
Authors: Krishnamurthy, Gnanavel Vaidhyanathan 
Chirumamilla, Manohar 
Rout, Surya Snata 
Pagnan Furlan, Kaline  
Krekeler, Tobias 
Ritter, Martin  
Becker, Hans Werner 
Petrov, Alexander  
Eich, Manfred 
Störmer, Michael 
Issue Date: 8-Feb-2021
Publisher: Macmillan Publishers Limited, part of Springer Nature
Source: Scientific Reports 11 (1): 3330 (2021-02-08)
Abstract (english): 
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
DOI: 10.15480/882.3485
ISSN: 2045-2322
Journal: Scientific reports 
Institute: Optische und Elektronische Materialien E-12 
Betriebseinheit Elektronenmikroskopie M-26 
Keramische Hochleistungswerkstoffe M-9 
Integrated Ceramic-based Materials Systems M-EXK3 
Document Type: Article
Project: SFB 986: Teilprojekt C1 - Strukturierte Emitter für effiziente und effektive Thermophotovoltaik 
SFB 986: Teilprojekt C7 - Deposition und Stabilität von hochtemperaturfesten geschichteten Metamaterialien 
SFB 986: Zentralprojekt Z3 - Elektronenmikroskopie an multiskaligen Materialsystemen 
License: CC BY 4.0 (Attribution) CC BY 4.0 (Attribution)
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