6533b7d7fe1ef96bd1268d6b

RESEARCH PRODUCT

Electronic Properties of Mixed-Valence Manganates:  The Role of Mn Substitutional Defects

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Single-phase perovskites in the solid solution series La0.7+yA0.3-yMn1-xMxO3 (with 0.00 ≤ x ≤ 0.10; A = Sr2+, M = Cu2+, Zn2+, Sc3+, Cr3+, Co3+, and Ga3+; A = Ba2+, M = Cu2+, Zn2+, and Sc3+) have been prepared via the acetic acid solutions freeze-drying method. This soft procedure makes possible strict stoichiometric control, and the synthetic variables allow one to maintain a constant proportion of Mn4+ (ca. 32%) in the 47 compounds prepared. In this way, the concentration of cationic vacancies at A and B sites is practically negligible in all cases. X-ray powder diffraction patterns corresponding to the 47 compounds have been completely indexed with rhombohedral perovskite cells. The crystal structures have been refined in space group R3c, in the hexagonal setting, from room-temperature data. The variation with x of a set of structural parameters (rhombohedral cell volume, rhombohedral cell angle, and B−O and A−O bond lengths) has been considered as a function of the mean sizes of cations at A and B sit...