CALORIMETRIC AND ELECTROPHYSICAL STUDIES OF LANTHANUM–POTASSIUM CUPRATE–VANADATE–MANGANITE

Kasenov B.K., Kasenova Sh.B., Sagintayeva Zh.I., Kuanyshbekov E.E.

Chemical and Metallurgical Institute named after J. Abishev

100009, Karaganda, Republic of Kazakhstan, Ermekova Street, 63

Perovskite manganites are of interest due to their enormous magnetoresistance, giant magnetostriction, and their potential for creating new functional materials.

The calorimetric study of LaK₂CuVMnO_7.5 was conducted in the range of 298.15-673 K using the IT-C-400 calorimeter.

The C⁰_p~f(T) curve shows λ-shaped peaks at 323 and 473 K (see Figure), which are characteristic of second-order phase transitions.

Temperature dependence of heat capacity LaK₂CuVMnO_7.5

Taking into account the temperatures of phase transitions, the equations describing the dependence C⁰_p~f(T) are derived. Based on the experimental dependence of the heat capacity and the calculated value of S⁰(298,15), the thermodynamic functions C⁰_p(T), S⁰(T), H⁰(T)-H⁰(298,15) and Ф^xx(Т) are calculated.

The electrophysical characteristics of LaK₂CuVMnO_7,5 were studied using the LCR 781 setup in the range of 293-483 K at frequencies of 1, 5, and 10 kHz. At a frequency of 1 kHz, there is a sharp increase in capacitance and dielectric constant with increasing temperature (ε ≈ 7×10⁸ at 483 K), accompanied by a decrease in resistance from ~4×10⁵ to <7.6×10² Ohm.

This research is funded by the Committee of Industry of the Ministry of Industry and Construction of the Republic of Kazakhstan under program-targeted funding for scientific research for 2024-2026, BR23991563: «Creation of Innovative Resourch-Saving Technologies for Mining and Integrated Processing of Mineral and Technogenic Raw Materials.