Solid Solutions of WO3into Zirconia in WO3–ZrO2 Catalysts

摘要: Abstract Catalysts in the WO 3 –ZrO 2 system were produced by coprecipitation of aqueous solutions zirconium oxynitrate and ammonium metatungstate. Samples characterized X-ray powder diffraction, thermogravimetry, refinement their crystalline structures with Rietveld method. This gave rise to solid tungsten oxide into zirconia; initial phase was amorphous crystallized two tetragonal phases, T1 T2, when samples annealed at 560°C. The main difference between both phases oxygen position along c axis. In higher symmetry, an atom one-half unit cell, 0.50(2), producing flat crystallite surfaces perpendicular axis, while lower T1, it 0.447(2), rough parallel (100) planes. interpenetrating tetrahedra forming representative polyhedron structure almost nondeformed because all Zr–O bond lengths very similar. As annealing temperature sample increased, dissolved atoms symmetry segregated crystallite's surface.