Phase transitions in crystalline [M(H2O)6](ClO4)2 (M=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd and Hg)

• Published in: Journal of thermal analysis and calorimetry 1998, Vol.54 (1), p.93-102
• Main Authors: MIKULI, E, MIGDAŁ-MIKULI, A, MAYER, J
• Format: Article
• Language: English
• Subjects: Anomalies; Cadmium; Cobalt; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Copper; Cross-disciplinary physics: materials science; rheology; Crystal structure; Crystallinity; Exact sciences and technology; Iron; Magnesium; Manganese; Materials science; Melting points; Mercury (metal); Nickel; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase transitions; Physics; Solid phases; Zinc
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1023/A:1010112801504

The results of DSC measurements in the temperature range 140–370 K on nine crystalline compounds of the type [M(H2O)6](ClO4)2, where M=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd and Hg, are discussed. Anomalies detected in the DSC curves are related to the existence of solid-solid phase transitions and/or to the melting points of these compounds. In consequence of two different hypothetical structural modifications of [Fe(H2O)6](ClO4)2, two DSC curves are obtained. For the compounds with M=Fe, Cd and Hg, new phase transitions have been discovered. The transition temperatures of the other phase transitions are in good agreement with literature data obtained by adiabatic calorimetry. For the compounds with M=Mg, Ni and Cd, DTA measurements were also carried out and the melting points of theses compounds were established.