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Hydride Reduction of BaTiO3 – Oxyhydride vs O-Vacancy Formation

Nedumkandathil, Reji (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Jaworski, Aleksander (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Grins, Jekabs (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
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Bernin, Diana (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Karlsson, Maths (author)
Österberg, Carin (author)
Neagu, Alexandra (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Tai, Cheuk-Wai (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Pell, Andrew J. (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
Häussermann, Ulrich (author)
Stockholms universitet,Institutionen för material- och miljökemi (MMK)
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 (creator_code:org_t)
English.
Related links:
https://urn.kb.se/re...
  • Other publication (other academic/artistic)
Abstract Subject headings
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  • We investigated the hydride reduction of tetragonal BaTiO3 using the metal hydrides CaH2, NaH, MgH2, NaBH4 and NaAlH4. The reactions employed molar BaTiO3:H ratios of up to 1.8 and temperatures near 600 °C. The air stable reduced products were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy, thermogravimetric analysis (TGA) and solid-state 1H NMR spectroscopy. PXRD showed the formation of cubic products - indicative of the formation of BaTiO3-xHx - except for NaH. Lattice parameters were in a range between 4.005 Å (for NaBH4 reduces samples) and 4.033 Å (for MgH2 reduced samples). With increasing BaTiO3:H ratio, CaH2, NaAlH4 and MgH2 reduced samples were afforded as two-phase mixtures. TGA in air flow showed significant weight increase of up to 3.5 % for reduced BaTiO3, suggesting that metal hydride reduction yielded oxyhydrides BaTiO3-xHx with x values larger 0.5. 1H NMR, however, revealed rather low concentrations of H, and, thus a simultaneous presence of O vacancies in reduced BaTiO3. It has to be concluded that hydride reduction of BaTiO3 yields complex disordered materials BaTiO3-xHy□(x-y) with x up to 0.6, y in a range 0.05 – 0.2 and (x-y) > y, rather than homogeneous solid solutions BaTiO3Hx. Resonances of (hydridic) H substituting O in the cubic perovskite structure appear in the -2 to -60 ppm spectral region. The large range of chemical shifts and breadth of the signals signifies the structural disorder in BaTiO3-xHy□(x-y). Sintering of BaTiO3-xHy□(x-y) in a gaseous H2 atmosphere resulted in more ordered materials as indicated by considerably sharper 1H resonances.

Subject headings

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)
NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Keyword

Oxyhydrides
PXRD
NMR
Materials Chemistry
materialkemi

Publication and Content Type

vet (subject category)
ovr (subject category)

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