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Template-directed synthesis and characterization of microstructured ceramic Ce/ZrO2@SiO2 composite tubes

“…The composition is in accordance with the molar ratio Ce/Zr employed in the synthetic spray-coating procedure. It is known that the substitution of Ce 4+ (ionic radii = 111 pm) for Zr 4+ (ionic radii = 98 pm) stabilizes the tetragonal ZrO 2 structure [10]. As shown for the solid solution composition Ce 0.12 /Zr 0.88 O 2 [10], the formation of the tetragonal over the stable thermodynamic high temperature mono-clinic phase of ZrO 2 depends on the total energy E t = E l + γ S m , where E I is the lattice energy, γ is the surface energy, and S m is the molar surface.…”

“…It is known that the substitution of Ce 4+ (ionic radii = 111 pm) for Zr 4+ (ionic radii = 98 pm) stabilizes the tetragonal ZrO 2 structure [ 10 ]. As shown for the solid solution composition Ce 0.12 /Zr 0.88 O 2 [ 10 ], the formation of the tetragonal over the stable thermodynamic high temperature mono-clinic phase of ZrO 2 depends on the total energy E t = E l + γ S m , where E I is the lattice energy, γ is the surface energy, and S m is the molar surface. The two values of E I are nearly identical for the monoclinic and tetragonal phase (11016 vs 11011 kJmol −1 ) [ 16 ], so the favorite formation of one over the other is mainly determined by their individual surface energies γ (11.3 × 10 −5 Jcm 2 vs 7.5–7.7 × 10 −5 Jcm 2 ) [ 17 – 18 ].…”

“…The transformation into ordered crystalline mesoporous structures of composition Ce x Zr 1− x O 2 ( x = 0.4–0.8) has also been shown [ 9 ]. In these solid solutions ultrafine zirconia allows for a better mechanical behavior, which facilitates enhanced fracture toughness with critical stress intensities as high as 20 MPa m 1/2 [ 10 ]. With respect to catalysis, solid solutions of the composition Ce x Zr 1− x O 2 have been studied for the generation of hydrogen (e.g., in fuel cell applications), CO 2 reforming (e.g., for production of synthesis gas), direct methane oxidation (e.g., for solid oxide fuel cells), SOFCs [ 3 , 5 ] and electrochromic smart window applications [ 11 ].…”

Composition, surface structure, and thermal behavior of ZrO2 + TiO2/Ti and ZrO2 + CeO x + TiO2 composites formed by plasma-electrolytic oxidation

“…ZrO 2 , CeO x , and TiO 2 oxides are widely used in catalysis, including high temperature processes [1][2][3][4]. Having a peculiar combination of properties, ceramics based on zirconium dioxide are applied in different fields of power industry, metallurgy, the coal and chemical industry, aerospace technology, elec tronics, and medicine [5,6].…”