Abstract
The heat capacity of GdMeFe2O5(Me — Li, Na, K, Cs) is investigated within the temperature range of 298.15–673 K by a calorimetric method. λ-points are revealed in the C ○ p (T) curves at 448 K and 598 K in GdLiFe2O5, at 473 K and 573 K in GdNaFe2O5, at 448 K and 598 K in GdKFe2O5, and at 448 in GdCsFe2O5 related to a phase transition of the second kind. The temperature dependencies are calculated for the thermodynamic functions C ○ p (T), H ○(T)-H ○(298.15), S ○(T), and Φ**(T). The electrophysical characteristics of the synthesized ferrites are studied within the temperature range of 303–493 K: Effects similar to those found in the C ○ p (T) curves are also revealed in the logɛ(T) and logR (T) curves. The compositions are shown to exhibit a semiconductor-type electrical conductivity. At the T cond points of the ferrites, the semiconductor-type conductivity changes the metal type one and both the capacities and permittivities vary sharply, and that may be related to a ferroelectric phase transition (the Curie and the Neel points). These effects provide a certain possibility to clarify the nature of the λ-points in the C ○ p (T) curves.
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Original Russian Text © Sh.B. Kasenova, Zh.I. Sagintaeva, B.K. Kasenov, S.Zh. Davrenbekov, S.M. Sergazina, E.Zh. Zhumadilov, 2013, published in Teplofizika Vysokikh Temperatur, 2013, Vol. 51, No. 1, pp. 61–66.
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Kasenova, S.B., Sagintaeva, Z.I., Kasenov, B.K. et al. Heat capacity and electrophysical properties of GdMeFe2O5(Me — Li, Na, K, Cs)-type ferrites. High Temp 51, 54–59 (2013). https://doi.org/10.1134/S0018151X13010082
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DOI: https://doi.org/10.1134/S0018151X13010082