Synthesis of nanocrystalline barium-hexaferrite from nanocrystalline goethite using the hydrothermal method: Particle size evolution and magnetic properties

Technical Report · Sat Mar 01 04:00:00 EST 1997

DOI:https://doi.org/10.2172/459417· OSTI ID:459417

Penn, R L; Banfield, J F ^[1]; Voigt, J ^[2]

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1. Univ. of Wisconsin, Madison, WI (United States)
2. Sandia National Labs., Albuquerque, NM (United States). Ceramic Synthesis and Inorganic Chemistry Dept.

To characterize particle size/magnetic property relationships, 9 to 50 nm in diameter barium hexaferrite, BaFe{sub 12}O{sub 19} (BHF), particles were prepared using a new synthesis route. By replacing the conventional 50 to 100 nm particles of goethite with nanocrystalline goethite produced via the microwave anneal method of Knight and Sylva, nanocrystalline BHF was synthesized using the hydrothermal method. Evolution of particle size and morphology with respect to concentration and heat treatment time is reported. Hysteresis properties, including coercivity (0.2--1.0 kOe), magnetization saturation (0.1--33.4 emu/g), and magnetization remanence (0.004--22.5 emu/g) are discussed as a function of particle size. The magnetization saturation and remanence of the 7 nm particles is nearly zero, suggesting the superparamagnetic threshold size for BHF is around this size. In addition, the equilibrium morphology of BHF crystals was calculated to be truncated hexagonal prisms which was verified by experiment, and the isoelectric point, pH of 4.1, was measured for 18 nm BHF particles.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Office of Financial Management and Controller, Washington, DC (United States); National Science Foundation, Washington, DC (United States); National Physical Science Consortium (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 459417
• Report Number(s): SAND--97-0345C; CONF-970481--1; ON: DE97004205; CNN: NSF Grant EAR-9508171
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
EXPERIMENTAL DATA
FERRITES
HYDROTHERMAL SYNTHESIS
MAGNETIC PROPERTIES
MORPHOLOGY
PARTICLE SIZE