Low-Temperature Heat Capacities of Terbium Molybdate Phosphates M
2
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Tb(MoO4)(PO4) (MI = Na or K) |
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| Authors: | K S Gavrichev N N Smirnova M A Ryumin V M Gurevich A V Tyurin F M Spiridonov L N Komissarova V P Danilov |
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| Institution: | (1) Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991, Russia;(2) Institute of Chemistry, Nizhni Novgorod State University, Nizhni Novgorod, Russia;(3) Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119992, Russia;(4) Chemistry Faculty, Moscow State University, Vorob’evy gory, Moscow, 119992, Russia |
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| Abstract: | The heat capacities of Na2Tb(MoO4)(PO4) and K2Tb(MoO4)(PO4) were measured by adiabatic calorimetry at low temperatures (6.34–333.74 and 7.20–341.17 K, respectively). Smoothed thermal-capacities values were used to calculate the entropy, enthalpy increments, and reduced Gibbs energy. The respective values at 298.15 K are as follows: for Na2Tb(MoO4)(PO4), C p 0 (298.15 K) = 240.1 ± 0.2 J/(K mol), 0 (298.15 K) = 307.4 ± 0.4 J/(K mol), H 0(298.15 K) ? H 0(0) = 44.95 ± 0.03 kJ/mol, and Φ0(298.15 K) = 156.6 ± 0.5 J/(K mol); and for K2Tb(MoO4)(PO4): C p 0 (298.15 K) = 245.1 ± 0.1 J/(K mol), S 0(298.15 K) = 322.9 ± 0.1 J/(K mol), H 0(298.15 K) ? H 0(0) = 46.58 ± 0.02 kJ/mol, and Φ0(298.15 K) = 166.6 ± 0.2 J/(K mol). The noncooperative magnetic component of the heat capacity was estimated. |
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