Synthesis of hexagonal Al2−xCrxO3 nanodisks by a thermal decomposition of mesoporous Cr4+:Al2O3 powders
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Monodispersed hexagonal Al2−xCrxO3 nanodisks are synthesized through a reactive doping of Cr6+ cations in a hydrogenated mesoporous AlO(OH)·αH2O powder followed by annealing at 1,200 °C in air. The reaction was carried out by a drop wise addition of an aqueous Cr6+ solution (0.5–1.0 M) to AlO(OH)·αH2O, at room temperature. Al2−xCrxO3 nanostructure formation was controlled by the nucleation and growth from the intermediate amorphous mesoporous Cr4+:Al2O3 composites in the temperature range 400–1,000 °C. The nanodisks of ∼50 nm diameter and thickness of ∼16 nm is observed in the sample with x of 0.2 and similar nanodisks with a low dimension is observed at a higher value of x of 1.6 (after 2 h of heating at 1,200 °C). The Cr3+ ↔ Al3+ substitution, x ≤ 1.2, inhibits grain growth in small crystallites. The crystallites in x = 0.2 composition have 43 nm diameter while it is 15 nm in those with x = 1.2 composition.
KeywordsDifferential Scanning Calorimetry Transmission Electron Microscope Micrograph Precursor Powder Drop Wise Addition Octahedral Interstitial Site
This work has been financially supported by the Council of Scientific & Industrial Research (CSIR) and the Defense Research & Development Organization (DRDO), Government of India.
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