Synthesis, crystal structure and magnetic properties of a new ruthenium (V) oxide: La_(1.2)S_(2.7)RuO_(7+delta)

摘要

Polycrystalline La_(1.2)S_(2.7)RuO_(7+delta) has been synthesized by standard ceramic techniques. The powder X-ray diffraction data of this phase, in which ruthenium is in a pentavalent state, has been indexed in the trigonal space group R3-bar m, with cell constants a = 5.750(1) A and c = 18.349(3) A. Along the c-axis, the structure can be described in terms of uniform stacking of two AO_3 layers and one A_2O_(1+delta) layer (A = La/Sr). The A cations in the A_2O_(1+delta) layer are trigonal-prismatically coordinated and the Ru ions occupy the octahedral sites between the AO_3 layers. La_(1.2)S_(2.7)RuO_(7+delta) is anew n = 2 member of the general family of [A_2O_(1+delta)] [A_nB_(n-1)O_(3n)] hexagonal perovskites with n representing the number of AO_3 successive layers. delta was found to be approximately 0.35. Synthesis, XRD-Rietveld analysis, thermogravi-metric investigations, XANES spectroscopy and magnetic behavior of this compound are discussed.