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Ni 1− x Co x Fe 1.98 O 4 Ferrite Ceramics with Promising Magneto‐Dielectric Properties
Author(s) -
Chan Kheng Chuan,
Liew Xiao Tian,
Kong Ling Bing,
Li Zheng Wen,
Lin Guo Qing
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02777.x
Subject(s) - materials science , sintering , dielectric , microstructure , ferrite (magnet) , ceramic , analytical chemistry (journal) , magnetocrystalline anisotropy , atmospheric temperature range , dissipation factor , dielectric loss , grain growth , mineralogy , composite material , magnetic anisotropy , magnetization , magnetic field , thermodynamics , chemistry , optoelectronics , physics , quantum mechanics , chromatography
The dielectric and magnetic properties of Ni 1− x Co x Fe 1.98 O 4 (with x =0.005, 0.01, 0.02, and 0.05) ferrite ceramics, doped with 5% Bi 2 O 3 as a sintering aid, were investigated. X‐ray diffraction results indicated that there is no obvious reaction between Bi 2 O 3 and the ferrites within the temperature range. All samples were fully densified after sintering at temperatures of ≥1000°C for 2 h. Densification behavior, microstructural development, and grain growth of the Ni 1− x Co x Fe 1.98 O 4 ferrite ceramics are independent of the concentration of Co. The appropriate sintering temperature range for achieving a low dielectric loss tangent is 1000°–1050°C. The high dielectric loss tangent of the samples sintered at temperatures of <1000°C is due mainly to the conduction losses caused by their porous microstructures, while that of the samples sintered at temperatures of >1050°C is not readily explainable at the moment. The variation in the magnetic properties (static permeability) can be understood in terms of the magnetocrystalline anisotropic constant combined with the single‐ion model. Promising magneto‐dielectric properties have been obtained in Ni 0.99 Co 0.01 Fe 1.98 O 4 and Ni 0.98 Co 0.02 Fe 1.98 O 4 , both sintered at 1050°C for 2 h, over 3–30 (high frequency) and 30–90 MHz, respectively. Such materials might find potential applications such as in antenna miniaturizations.