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Thermal stability and oxidation resistance of polycrystalline Ba 8 Al 16 Si 30 ‐based clathrates
Author(s) -
Anno Hiroaki,
Shirataki Ritsuko
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201300145
Subject(s) - analytical chemistry (journal) , x ray photoelectron spectroscopy , crystallite , materials science , spark plasma sintering , thermal stability , thermogravimetry , scanning electron microscope , barium , differential thermal analysis , electrical resistivity and conductivity , mineralogy , sintering , chemistry , diffraction , chemical engineering , metallurgy , inorganic chemistry , composite material , optics , physics , electrical engineering , organic chemistry , chromatography , engineering
Polycrystalline Ba 8 Al 16 Si 30 ‐based clathrate samples (nominal composition Ba 8 Al 15 Si 31 ) were prepared by combining arc melting and spark plasma sintering methods. Heat treatments were conducted at 873 K for 0–480 h in air to examine the thermal stability and the oxidation resistance, which are of practical importance when the material is used at elevated temperatures. Thermogravimetry (TG) and differential thermal analysis (DTA) in the range 300–1473 K in air indicated that Ba 8 Al 15 Si 31 bulk form possessed relatively good thermal stability in air below approximately 1073 K. From X‐ray diffraction measurements, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy, it was inferred that thin oxide (probably barium aluminates) layer with the thickness of approximately 0.6 µm was formed on the surface by the heat treatment. The decrease in the electrical conductivity was found to be relatively low (less than 15%) by the heat treatment for 480 h in air.