Preparation and Characterization of <alpha>-Fe2O3 polyhedral nanocrystals via annealing technique

TL;DR

This study reports the synthesis of uniform polyhedral alpha-Fe2O3 nanocrystals via annealing FeCl3 on silicon at high temperature with controlled gas flow, and characterizes their morphology and crystalline structure.

Contribution

It introduces a method for producing well-defined alpha-Fe2O3 nanocrystals with controlled shape and size using annealing in a specific gas environment, with detailed characterization.

Findings

Polyhedral nanocrystals form at 1000°C with specific gas flow rates.

Nanocrystal shape and size depend on annealing temperature and gas flow.

Crystalline structure confirmed by HRTEM and SADP.

Abstract

Polyhedral nanocrystals of <alpha>-Fe2O3 are successfully synthesized by annealing FeCl3 on silicon substrate at 1000 oC in the presence of H2 gas diluted with argon (Ar). Uniformly shaped polyhedral nanoparticles (diameter ~50-100 nm) are observed at 1000 oC and gases flow rate such as; Ar = 200 ml/min and H2 = 150 ml/min. Non-uniform shaped nanoparticles (diameter ~ 20-70 nm) are also observed at an annealing temperature of 950 oC with lower gases flow rate (Ar = 100 ml/min and H2 = 75 ml/min). Nanoparticles are characterized in detail by field-emission electron microscopy (FE-SEM), energy dispersive x-ray (EDX) and high resolution transmission electron microscopy (HRTEM) techniques. HRTEM study shows well resolved (110) fringes corresponding to <alpha>-Fe2O3, and selected area diffraction pattern (SADP) confirms the crystalline nature of <alpha>-Fe2O3 polyhedral nanoparticles. It is observed that polyhedral formation of <alpha>-Fe2O3 nano crystals depends upon annealing temperature and the surface morphology highly rely on the gas flow rate inside the reaction chamber.