| Abstrakt: |
In this work, different materials of Nd2CuO4 and K2NiF4 Ruddlesden-Popper structure have been prepared by solid-state reaction in air and high temperatures. The powders of mixed oxides, of general formula La2Li0.5M0.5 − xAuxO4 (M = Cu, Ni), were prepared from [Au(NH3)4](NO3)3 as gold source. The stoichiometric proportions of the all reagents (including La2O3, NiCO3, CuO) were grounded with a LiOH excess as mineralizer, pressed to form into pellets and heated in static air at temperatures between 750 and 850 °C for several hours. Structural characterization of the synthesized oxides using X-ray diffraction (XRD) are presented. La2Li0.5Au0.5O4, La2Li0.5Cu0.5O4, and La2Li0.5Ni0.5O4, three previously known oxides, were obtained. As expected, La2Li0.5Ni0.5O4 and La2Li0.5Cu0.5O4 consist of an ordered K2NiF4 Ruddlesden-Popper structure, while the La2Li0.5Au0.5O4 compound exhibits a Nd2CuO4 type structure. On the other hand, the preparation of the new proposed group La2Li0.5M0.5 − xAuxO4 (x = 0.0125-0.5) containing gold and nickel/copper simultaneously, under the studied conditions, was not possible. The experimental results revealed that the host structures are intolerant with respect to M (Cu or Ni) and Au cation double substitution. The difficulty to obtain the new phases is discussed regarding the exceptional instability displayed by the trivalent state of gold ion (Au3+) and the soft interactions of this specie with the lithium cation. Finally, the monophasic oxides, more interesting in terms of catalytic activity, were analyzed by temperature-programmed reduction (TPR-H2). [ABSTRACT FROM AUTHOR] |
