Аңдатпа
Abstract We study the temperature dependences of the specific heat of nanostructured lanthanum and sodium copper–zinc manganite LaNa2CuZnMnO6 by dynamic calorimetry in the temperature range 298.15–673 K. The curve of specific heat dependence on temperature at 348 K shows a jump, probably related to a phase transition of the second kind. We derive the equations for the temperature dependence of specific heat, taking the phase transition temperature into account. The standard entropy is calculated, and the temperature dependences of the thermodynamic functions of the studied manganite are determined. The temperature dependence of the electrical resistance is studied in the range of 293 to 483 K using an LCR meter (Taiwan); at 343 K, the possible semiconductor conductivity transforms into a metallic one; and at 443 K, the metallic conductivity transforms into a semiconductor one. The bandgaps are calculated.