Preparation and characterization of LaMn1−xCUxO3+λ perovskite oxides

doi:10.1016/0021-9517(90)90102-P

Journal of Catalysis

Volume 124, Issue 1, July 1990, Pages 41-51

https://doi.org/10.1016/0021-9517(90)90102-P Get rights and content

Abstract

Compounds of nominal composition LaMn_1−xCu_x0_3+λ, (0 ⪯ × ⪯ 1) have been prepared and characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). Substitution of manganese by copper up to x = 0.6 preserves the perovskite structure. For x = 0.8, in addition to the perovskite, La₂CuO₄ and CuO were formed. For x = 1, the only phases present were La₂CuO₄ and CuO. The perovskites showed oxidative nonstoichiometry for x ⪯ 0.4 and reductive nonstoichiometry for x = 0.6. Stoichiometry was reached for x = 0.5. XPS results for LaMn_0.6Cu_0.4O_3+λ reduced at 473–753 K are indicative of sintering of the copper particles when reduction is effected above 673 K. The TPR curve for LaMnO_3+λ showed an inflection point at ca. 0.5 e⁻ per molecule which nearly corresponds to reduction of the estimated oxygen excess in the sample. Samples with substitutions 0 ⪯ × ⪯ 0.6 showed two reduction steps of Cu²⁺ to Cu⁰ and of Mnⁿ⁺ ( $n ⪰ 3$ ) to Mn²⁺. In the fully substituted sample (x = 1) reduction of CuO and reduction of La₂CuO₄ can be clearly distinguished. Reduction of perovskites of low copper content (x < 0.5) at 673 K or below yielded highly dispersed copper catalysts.

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Preparation and characterization of LaMn1−xCUxO3+λ perovskite oxides

Abstract

Physica

J. Solid State Chem.

J. Catal.

J. Solid State Chem.

Mater. Res. Bull.

Mater. Res. Bull.

Mater. Chem. Phys.

J. Catal.

J. Catal.

Mater. Res. Bull.

J. Catal.

J. Catal.

Appl. Surf. Sci.

J. Catal.

Physica

Mater. Res. Bull.

J. Catal.

Ann. N. Y. Acad. Sci.

Preparation and characterization of LaMn_1−xCU_xO_3+λ perovskite oxides