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The Effect of Dopant Concentration in the Nd1 – xAxMnO3Solid Solutions (A = Ba, Sr) on the Electrical Conductivity and Structural Transitions in the Temperature Range 20–1200°C
Doklady Physical Chemistry  (IF0.638),  Pub Date : 2020-06-01, DOI: 10.1134/s0012501620360014
O. M. Fedorova, L. B. Vedmid’, G. A. Kozhina, V. B. Balakireva, V. F. Balakirev

Abstract The Jahn–Teller effect in Nd 1 – x A x MnO 3 manganites (A = Ba, Sr; x = 0.15, 0.25) was studied by high-temperature X-ray diffraction and differential scanning calorimetry. The bond lengths and angles of the MnO 6 octahedron characterizing the Jahn–Teller distortion were first determined for these compositions by the Rietveld method. It was found that the temperature of removal of this distortion was markedly lower than that for the undoped compound. The temperature dependences of the electrical conductivity of all the above samples were measured for the first time. The highest electrical conductivity was found for Nd 0.75 Sr 0.25 MnO 3 . A decrease in the strontium concentration to 15 mol % decreased the electrical conductivity by almost half. Replacing strontium with barium also decreased the electrical conductivity, which was especially noticeable at low temperatures. The effective activation energy of electrical conductivity was characteristic of the polaron charge transfer mechanism.