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Li 2 MoO 4 ‐based composite ceramics fabricated from temperature‐ and atmosphere‐sensitive MnZn ferrite at room temperature
Author(s) -
Väätäjä Maria,
Kähäri Hanna,
Juuti Jari,
Jantunen Heli
Publication year - 2017
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/jace.14914
Subject(s) - materials science , ferrite (magnet) , sintering , ceramic , composite number , composite material , dielectric , microstructure , optoelectronics
The first magnetic ceramic composites manufactured, using the room‐temperature densification method are reported. The samples were prepared at room temperature using Li 2 MoO 4 as a matrix and MnZn ferrite with loading levels of 10‐30 vol‐% followed by postprocessing at 120°C. The method utilizes the water solubility of the dielectric Li 2 MoO 4 and compression pressure instead of high temperatures typical of conventional solid‐state sintering. Hence, composite manufacturing using temperature‐ and atmosphere‐sensitive materials is possible without special conditions. This was demonstrated with MnZn ferrite, which is prone to oxidation when heat treated in air. Samples manufactured with room‐temperature densification showed no signs of reactivity during processing, whereas reference samples sintered at 685°C suffered from oxidation and formation of an additional reaction phase. The densities achieved with different loading levels of MnZn ferrite with both methods were very similar. Measurements up to 1 GH z showed relatively high values of relative permittivity (21.7 at 1 GH z) and permeability (2.6 at 1 GH z) with 30 vol‐% loading of MnZn ferrite in the samples manufactured by room‐temperature densification. In addition, pre‐granulation is proposed to improve the processability of the composite powders in room‐temperature densification.