Ceria-zirconia crystal structure

Ceria-zirconia nanophases were synthesied by a surfactant-assisted method. The refined structural data concerning the crystallite size, lattice parameters, structural microstrain, cationic occupy number and cationic defect concentration are reported. Zirconium addition into the cubic structure of ceria inhibits crystal sintering but leads to structure distortion. Different CO-metal bonds are formed when CO chemisorbs on Pd-loaded CesZr. x02 catalysts. Catalytic tests reveal that the lower zirconium content benefits the CO oxidation. 

Nanosized ceria-zirconia materials with improved thermal stability can be prepared by using the surfactant-assisted method. Structural refinements confirm that the nanocrystals contain structural microstrain and cationic lattice defects. Zirconium addition to ceria supresses the crystal sintering and imporves the thermal stability but leads to structure distortion. Both catalytic tests and CO-chemisorption show that Pd supported ceria-zirconia nanoparticles are active for CO oxidation. 

CRYSTAL AND ELECTRONIC STRUCTURES, STRUCTURAL DISORDER, PHASE TRANSFORMATION, AND PHASE DIAGRAM OF CERIA-ZIRCONIA AND CERIA-BASED MATERIALS... 

Ceria-zirconia materials exhibit high catalytic activity and are used for exhaust gas cleaning. To understand the catalytic activity of ceria-zirconia materials, a knowledge of the phases and the crystal structure of zirconia and ceria-zirconia solid solutions is important. 

Figures 1.23(c) and (d) show the optimized crystal structure and isosurface of the corresponding valence-electron density distribution of ceria (CegOje supercell) The optimized unit-cell parameters agree with the experimental values. The relation c = S.a and optimized atomic coordinates indicate that the ceria has a cubic fluorite-type structure. The calculated valence-electron density distribution of ceria is consistent with the experimental data. In comparison with the Zr-O bonds in zirconia (Fig. 1.23(b)), the Ce-O bond in ceria is more ionic (Fig. 1.23(d)).

Figure 1.25 shows the optimized crystal structure and isosurlace of the corresponding valence-electron density distribution of the tetragonal (t ) ceria-zirconia solid solution Ceo jZro The calculated tetragonal unit-cell parameters agree with experimental values. ... 

In this chapter, I reviewed the crystal structure, electronic structure, structural disorder, phase transformation, and phase diagrams of ceria-zirconia and ceria-based materials. 

Lanthanum molybdate, LaiMoiOg, has been reported to exhibit fast oxide ion conducting properties comparable with the conventional zirconia and ceria compositions. This compound presents a different crystal structure from all known oxide electrolytes, and consists of isolated [Mo04] units in a three-dimensional matrix of [LaiO]" " . La2Mo209 undergoes a reversible phase transition from the non-conductive monoclinic a-form to the highly conductive cubic -form at approximately 580 °C. Powder X-ray diffraction (XRD) of the phases a and fl are practically identical, because the structural phase transition a is actually a transition from a static to dynamic distribution of the oxygen defects... 

---