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Preparation of Monodisperse ε‐Fe 2 O 3 Nanoparticles by Crystal Structural Transformation
Author(s) -
Nakaya Masafumi,
Nishida Ryo,
Hosoda Natsumi,
Muramatsu Atsushi
Publication year - 2017
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.201700110
Subject(s) - nanoparticle , orthorhombic crystal system , dispersity , materials science , phase (matter) , crystal structure , coercivity , crystal (programming language) , chemical engineering , crystallography , analytical chemistry (journal) , nanotechnology , chemistry , organic chemistry , polymer chemistry , engineering , computer science , programming language , physics , condensed matter physics
Monodisperse iron oxide nanoparticles in the ε‐Fe 2 O 3 phase, which is the rare orthorhombic phase among the four crystal systems of Fe 2 O 3 , are prepared via crystal structural transformation induced by heat treatment of SiO 2 ‐coated monodisperse FeO nanoparticles. The mean diameter of the resulting ε‐Fe 2 O 3 nanoparticles is 41.0 ± 4.2 nm. Compared with the as‐synthesized 40.9 ± 3.8 nm‐FeO nanoparticles, which are used as the precursor, the size and size distribution of the nanoparticles remain almost unchanged after heat treatment. By optimizing the thickness of the SiO 2 shell, coalescence of the nanoparticles during heat treatment can be prevented. XRD measurements do not detect the α‐Fe 2 O 3 phase and γ‐Fe 2 O 3 phase in the obtained sample. The resulting ε‐Fe 2 O 3 nanoparticles exhibit a high coercivity of 23.4 kOe at room temperature.