Structure and thermal decomposition of ammonium metatungstate

Dávid Hunyadi, I. Sajó, Imre Miklós Szilágyi

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The structure and morphology of ammonium metatungstate (AMT), (NH 4)6[H2W12O40] ·4H2O, and its thermal decomposition in air and nitrogen atmospheres were investigated by SEM, FTIR, XRD, and TG/DTA-MS. The cell parameters of the AMT sample were determined and refined with a full profile fit. The thermal decomposition of AMT involved several steps in inert atmosphere: (i) release of crystal water between 25 and 200 °C resulting in dehydrated AMT, (ii) formation of an amorphous phase between 200 and 380 °C, (iii) from which hexagonal WO3 formed between 380 and 500 °C, and (iv) which then transformed into the more stable m-WO3 between 500 and 600 °C. As a difference in air, the as-formed NH3 ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH4)10[H2W12O 42]·4H2O, the only main difference being the lack of dry NH3 evolution between 170 and 240 °C in the case of AMT.

Original languageEnglish
Pages (from-to)329-337
Number of pages9
JournalJournal of Thermal Analysis and Calorimetry
Volume116
Issue number1
DOIs
Publication statusPublished - 2014

Fingerprint

thermal decomposition
Pyrolysis
decomposition
combustion products
inert atmosphere
nitrous oxides
air
temperature effects
thermal analysis
nitrogen
atmospheres
scanning electron microscopy
profiles
cells
water
crystals
Nitrous Oxide
Air
Ammonium Compounds
Thermal effects

Keywords

  • Ammonium metatungstate
  • FTIR
  • MS
  • TG/DTA
  • XRD

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Condensed Matter Physics

Cite this

Structure and thermal decomposition of ammonium metatungstate. / Hunyadi, Dávid; Sajó, I.; Szilágyi, Imre Miklós.

In: Journal of Thermal Analysis and Calorimetry, Vol. 116, No. 1, 2014, p. 329-337.

Research output: Contribution to journalArticle

Hunyadi, Dávid ; Sajó, I. ; Szilágyi, Imre Miklós. / Structure and thermal decomposition of ammonium metatungstate. In: Journal of Thermal Analysis and Calorimetry. 2014 ; Vol. 116, No. 1. pp. 329-337.
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