Innovative Approaches to Oxide Nanosystems: CeO₂‐ZrO₂ Nanocomposites by a Combined PE‐CVD/Sol–Gel Route

Abstract

A novel combined PE-CVD/sol±gel approach to oxide-based nanosystems is proposed and employed for the synthesis of CeO 2 ±ZrO 2 nanocomposites. The method consists of the plasma-enhanced (PE) CVD of ceria (guest) on a zirconia xerogel ZrO x (OH) y (OR) z (host) prepared by sol±gel (SG) at a temperature of 200 C. The system evolution under annealing in air (600 C and 900 C, 1 h) and its mutual relationships with the synthesis conditions were investigated in detail by a multi-technique characterization. The proposed synthetic pathway enables the synthesis of CeO 2 ±ZrO 2 nanostructured systems ranging from composites to solid solutions, as a function of thermal treatment and Ce/Zr ratio as well. In this framework, particular attention is devoted to achieving an intimate Ce/Zr intermixing by exploiting the synergy between the SG xerogel properties (porosity, ±OH content) and the peculiar actions exerted by plasma (ablation/deposition, infiltration power). Such features enable an in-depth penetration of ceria into the inner zirconia xerogel layers already in the as-grown systems.

Temperature‐Controlled Synthesis and Photocatalytic Performance of ZnO Nanoplatelets

“…[6,24] To this regard, while CVD experiments performed in the absence of water produced an isotropic growth (see above), water vapor introduction into the reaction ambient enhanced the precursor decomposition (Fig. 5a), [36] leading to a higher deposition rate and to a different growth mechanism (see above and Fig. 1).…”

Functional Metal Oxide Nanosystems by a Hybrid CVD/Sol–Gel Approach

“…The latter feature, along with the plasma bombarding action discussed above, is responsible for the in-depth Ce penetration already in the as-prepared specimens, as confirmed by XPS analyses. [11] This result is an important prerequisite for obtaining CeO 2 -ZrO 2 nanosystems, the properties of which can be subsequently tailored by suitable thermal treatments. In fact, the intimate host/guest intermixing at a molecular level facilitates the subsequent diffusive processes and eventual solid state reactions between the two oxides.…”

“…In particular, LaCoO 3 thin films were obtained by a thermal-CVD/SG route, while CeO 2 -ZrO 2 materials were synthesized by a plasma-enhanced (PE)CVD/SG approach. [11] In the present work, special emphasis is given to a comparative discussion of the system behavior and, in particular, to the possibility of obtaining different material properties as a function of the adopted synthesis method. Preliminary results have already been briefly reported.…”

“…In the last decade, the attention of our research group has been addressed to the preparation and characterization of LaCoO 3 and CeO 2 -ZrO 2 nanosystems, both in the form of powders and thin films. [11][12][13][14][15] In particular, one of the main aims has been to elucidate the correlations existing between the synthesis parameters and the chemicophysical properties of the resulting nanomaterials. Based on the know-how acquired in the fields of CVD and SG processing, during the last few years we have developed an innova-tive hybrid CVD/SG approach to oxide nanosystems, entailing a synergistic exploitation of CVD and SG characteristics and flexibility.…”

“…The peculiarities of this preparative approach have already been outlined. [11,12] A relevant feature which is worth recalling is the combination of CVD infiltration power [16,17] with the porosity and -OH content characterizing xerogel materials obtained by SG. [18] This phenomenon results in a remarkable host/guest intermixing already in the as-prepared systems, favoring, in turn, the subsequent system evolution under annealing.…”