Synthesis and crystal structure of a new oxychalcogenide La5Ti-3.25Zr_0.25S5O9.25

摘要

A new phase in the quinary system La/Ti/Zr/S/O was obtained from a mixture of La2O3, La2S3, ZrO2, and TiO2 by a solid-state reaction at 1273 K in a sealed fused-silica tube. The structure of this new phase, La5Ti∼ 3.25Zr∼ 0.25S5O9.25, was solved by singlecrystal X-ray diffraction, with R-(obs) = 3.37% for 2764 reflections (I > 3σ(I)) and 125 variables. This compound crystallizes with four formula units in the monoclinic space group C2/m with lattice constants a = 18.401(2) &ANGS;, b = 3.9032(3) &ANGS;, c = 21.944(3) &ANGS;, and β = 106.100(8)°. The structure can be viewed as a 2D building constituted from two-atom-thick slabs of rock salt type ( = sulfide part) which are interleaved with double-octahedral chains centered on titanium/zirconium atoms (mixed Ti/Zr sites) and drawing a zigzag arrangement ( = oxide part). In addition, EDXS analyses show that a solid solution Ti/Zr exists with a general formulation La(5)Ti(3.5-x)Z(1x)S(5)O(9.25) (where 0. 1 ≤ x ≤ 0.5). © 2005 Elsevier Inc. All rights reserved.