Synthesis, Crystal Structure, and Thermal Properties of CaSO4·2H2O Single Crystals

  •  Takanori Fukami    
  •  Shuta Tahara    
  •  Keiko Nakasone    
  •  Chitoshi Yasuda    


Single crystals were grown at room temperature from the precursors CaCO3 and NH2SO3H by a gel method using agar-agar gel as the medium of growth. Differential scanning calorimetry, thermogravimetric–differential thermal analysis, and X-ray diffraction measurements were performed on the single crystals. The crystal structure of the grown crystals was confirmed to be very similar to that of calcium sulfate dihydrate (CaSO4·2H2O, gypsum). The temperature at which dehydration and evaporation of intercalated water molecules in the single crystal occurred was found to be 375.9 K, which was very close to that in CaSO4·2H2O. From all these results, we identified the grown single crystals as CaSO4·2H2O. The weight loss owing to the thermal decomposition of anhydrous CaSO4 formed by the dehydration of the single gypsum crystals was found to occur at ~1530 K. This weight loss was probably caused by the evolution of SO3 gas by sublimation, and the chalky white substance left in the open vessel after decomposition was calcium oxide (CaO).

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  • ISSN(Print): 1916-9698
  • ISSN(Online): 1916-9701
  • Started: 2009
  • Frequency: semiannual

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