Naslov
Impact of Mg2+ ion incorporation on the phase development of ZrO2-type solid solutions and their application in the catalytic oxidation of carbon monoxide

Autori
Nemec, Vinko ; Kaper, Helena ; Pétaud, Guillaume ; Ivanda, Mile ; Štefanić, Goran

Izvornik
Journal of molecular structure (0022-2860) 1140 (2017); 127-141

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
ZrO2-MgO ; Rietveld refinement ; Raman spectroscopy ; Catalysis ; Lattice parameters ; Solid solubility

Sažetak
The precursors of ZrO2-MgO system covering the whole concentration range were prepared by co-precipitation of the corresponding nitrate salts. The obtained precursors were calcined in air at different temperatures up to 1000 °C and analyzed at room temperature using X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESM) and energy dispersive X-ray spectrometry (EDS). Maximum solubility of Mg2+ ions (∼32 mol%) was obtained in the amorphous precursor. After crystallization at 600 °C the solid solubility of Mg2+ ions decreases to ∼26 mol% of which ∼22 mol% was incorporated inside ZrO2-type lattice while the remaining part of Mg2+ ions was adsorbed on the surface of the particles. Further thermal treatment decreases solubility of Mg2+ ions to 18 mol% (800 °C) and finally to 9 mol% (1000 °C). On the other side of the concentration range, the solubility of Zr4+ ions in MgO lattice was <1 mol%. The results of phase analysis, using Rietveld refinements of the powder diffraction patterns and Raman spectroscopy, show that the incorporation of Mg2+ ions partially stabilized both tetragonal ZrO2 (up to 10 mol%) and cubic ZrO2 (>10 mol%) polymorphs. A precise determination of unit-cell parameters shows that the increase in the Mg2+ content causes a decrease in the parameter c of tetragonal ZrO2 lattice, which in a solid solution with a Mg2+ content ≥10 mol% becomes very close to the lattice parameter a (approaching cubic lattice). The results of FE-SEM analysis show that the addition of Mg2+ ions promotes sintering of samples. The influence of thermal treatment on the crystallization of the amorphous precursors to ZrO2-type lattice was examined by differential thermal analysis and thermogravimetric measurement. The obtained results show that the crystallization temperature increases with increasing Mg content, from 445 °C (0 mol% MgO) to 625 °C (∼50 mol% MgO). The ZrO2 doped with 3 mol% MgO was used as catalyst support for platinum nanoparticles and compared to commercially available 3% yttria-doped stabilized zirconia (3YSZ). The catalysts were used for catalytic CO oxidation and show slightly better performance of the ZrO2-MgO system, which demonstrates the potential of these materials as alternative catalyst support.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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