Li2MoO4-based composite ceramics fabricated from temperature- and atmosphere-sensitive MnZn ferrite at room temperature.
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| Title: | Li |
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| Authors: | Väätäjä, Maria1 maria.vaataja@oulu.fi, Kähäri, Hanna1, Juuti, Jari1, Jantunen, Heli1 |
| Source: | Journal of the American Ceramic Society. Aug2017, Vol. 100 Issue 8, p3626-3635. 10p. 1 Color Photograph, 1 Chart, 5 Graphs. |
| Subjects: | Ferrite circulators, Circulators (Electrical engineering), Ferrite devices, Ceramics, Construction materials |
| Abstract: | The first magnetic ceramic composites manufactured, using the room-temperature densification method are reported. The samples were prepared at room temperature using Li2MoO4 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 Li2MoO4 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 GHz showed relatively high values of relative permittivity (21.7 at 1 GHz) and permeability (2.6 at 1 GHz) 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. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | The first magnetic ceramic composites manufactured, using the room-temperature densification method are reported. The samples were prepared at room temperature using Li2MoO4 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 Li2MoO4 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 GHz showed relatively high values of relative permittivity (21.7 at 1 GHz) and permeability (2.6 at 1 GHz) 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. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00027820 |
| DOI: | 10.1111/jace.14914 |
