Heat Capacity and Thermodynamic Functions of Neodymium Orthoniobate

The heat capacity of polycrystalline neodymium orthoniobate NdNbO 4 in the range 2–1370 K is studied by relaxation, adiabatic, and differential scanning calorimetry. The existence of a magnetic transformation with a Néel temperature below 2 K in the low-temperature region is verified. The reversible...

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Bibliographic Details
Published in:Russian journal of inorganic chemistry 2021-02, Vol.66 (2), p.237-244
Main Authors: Nikiforova, G. E., Kondrat’eva, O. N., Tyurin, A. V., Ryumin, M. A., Khoroshilov, A. V., Gavrichev, K. S.
Format: Article
Language:English
Subjects:
Chemistry
Chemistry and Materials Science
Heat
Inorganic Chemistry
Low temperature
Neodymium
Phase transitions
Physicochemical Analysis of Inorganic Systems
Specific heat
Temperature dependence
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Summary:The heat capacity of polycrystalline neodymium orthoniobate NdNbO 4 in the range 2–1370 K is studied by relaxation, adiabatic, and differential scanning calorimetry. The existence of a magnetic transformation with a Néel temperature below 2 K in the low-temperature region is verified. The reversible phase transition at 987 K is shown to be a second-order transition. The contribution of the Schottky anomaly (Schottky contribution) to neodymium orthoniobate heat capacity is estimated. The gained data are used to calculate temperature-dependent standard thermodynamic functions in the range from 0 to 1400 K. Their values at 298.15 K are (298.15 K) = 121.4 ± 0.4 J/(K mol), S °(298.15 K) = 134.7 ± 0.5 J/(K mol), H °(298.15 K) – H °(0 K) = 21.24 ± 0.17 kJ/mol, Ф°(298.15 K) = 63.43 ± 0.21 J/(K mol).
ISSN:0036-0236
1531-8613
DOI:10.1134/S0036023621020145