부산대학교 도서관

The thermodynamic properties and phase transitions of Tutton salt [(N[H.sub.4]).sub.2]Fe[(S[O.sub.4]).sub.2]6[H.sub.2]O were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance. The first mass loss occurs around 330 K ([T.sub.d]), which is interpreted as the onset of partial thermal decomposition. Phase transitions were found at 387 K (= [T.sub.C1]) and 500 K (= TC2). The temperature dependences of the spin-lattice relaxation time in the rotating frame, [T.sub.1ρ], and that in the laboratory frame, [T.sub.1], for the H nuclei change abruptly near [T.sub.C1]. These changes are associated with changes in the geometry of the arrangement of octahedral water molecules and ammonium protons. Keywords Tutton salts * ([N[H.sub.4]).sub.2]Fe[(S[O.sub.4]).sub.2]6[H.sub.2]O * Thermodynamic property * MAS NMR * Solid NMR * Phase transition
Introduction Tutton salts have played a significant role in physics and chemistry; considerable attention is currently focused on the development of materials suitable for strong energy absorption by solar collectors. [...]