Polymorphic phase transition and thermal stability in squaric acid (H 2C 4O 4)

Kwang Sei Lee, Jin Jung Kweon, In Hwan Oh, Cheol Eui Lee

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14 Citations (Scopus)


Phase transformations in squaric acid (H 2C 4O 4) have been investigated by thermogravimetry and differential scanning calorimetry with different heating rates β. The mass loss in TG apparently begins at onset temperatures T di=245±5°C (β=5°C min -1), 262±5°C (β=10°C min -1), and 275±5°C (β=20°C min -1). A polymorphic phase transition was recognized as a weak endothermic peak in DSC around 101°C (T c +). Further heating with β=10°C min -1 in DSC revealed deviation of the baseline around 310°C (T i), and a large unusual exothermic peak around 355°C (T p), which are interpreted as an onset and a peak temperature of thermal decomposition, respectively. The activation energy of the thermal decomposition was obtained by employing relevant models. Thermal decomposition was recognized as a carbonization process, resulting in amorphous carbon.

Original languageEnglish
Pages (from-to)890-895
Number of pages6
JournalJournal of Physics and Chemistry of Solids
Issue number7
Publication statusPublished - 2012 Jul

Bibliographical note

Funding Information:
This work was supported by the 2008 Inje University research grant.


  • B: Crystal growth
  • C: Differential scanning calorimetry (DSC)
  • C: Thermogravimetric analysis (TGA)
  • C: X-ray diffraction
  • D: Phase transitions

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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