Elaboration and Characterization of Materials from the LaMnO3–BiMnO3 Binary System. Issue 6 (31st January 2020) - Djahmoum, Mourad
Abstract : The study of the La(1‐ x ) Bi x MnO3 system is conducted using X‐ray diffraction (XRD) and electrical measurements. A continuous solid solution is evidenced for the LaMnO3 rich part of this system ( x ≤ 0.6). According to the analyses of XRD results, a rhombohedral symmetry ( R 3 ¯ c ) is observed for x ≤ 0.4 and a cubic structure for x = 0.5. The structural study allows to determine an increase in the mean perovskite lattice parameter, together with a decrease in the rhombohedral angle up to a cubic symmetry for x = 0.5. For x > 0.6, the system is no more single‐phased. Impedance measurements are conducted for ceramics in a wide‐frequency range (100 Hz–1 MHz), between room temperature and 800 °C. The exponential decrease in the alternative current (AC) conductivities ( σ AC ) and the room temperature values correspond to a semiconducting behavior. Direct current (DC) conductivity measurements ( σ DC ) are also performed below room temperature (25 K < T < 300 K). The results evidence for a metal–insulator phase transition. For the exponential part of the σ DC curves, the gap energy is between 0.1 and 0.2 eV, confirming the semiconductor behavior of these materials. Abstract : The study of the La(1‐ x ) Bi x MnO3 system reveals a continuous solid–solution for x ≤ 0.6 (rhombohedral → cubic). Direct current (DC) conductivity measurements (25 K < T < 300 K) evidence a metal–insulator phase transition. The exponential decrease in the alternative current (AC) conductivities and room temperature values correspond to a semiconducting behavior, with a gap energy between 0.1 and 0.2 eV.