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A High‐ Q Microwave Dielectric Material Based on Mg 3 B 2 O 6
Author(s) -
Došler Urban,
Kržmanc Marjeta Maček,
Jančar Boštjan,
Suvorov Danilo
Publication year - 2010
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.1551-2916.2010.03926.x
Subject(s) - annealing (glass) , microstructure , materials science , amorphous solid , scanning electron microscope , analytical chemistry (journal) , dielectric , ceramic , grain growth , anisotropy , mineralogy , crystallography , crystal twinning , composite material , chemistry , optics , physics , optoelectronics , chromatography
The microwave dielectric properties and microstructure of Mg 3 B 2 O 6 ceramics with the addition of 0–5 wt% Mg 2 B 2 O 5 were investigated. Scanning electron microscopy of the Mg 3 B 2 O 6 ceramics sintered at 1310°C revealed the presence of anisotropic, exaggeratedly grown grains with a crystallographic fault that extends along the direction of the anisotropy. The most pronounced, exaggerated grain growth was observed for Mg 3 B 2 O 6 with 5 wt% of Mg 2 B 2 O 5 . The anisotropic grains were examined by electron backscatter diffraction. The analysis of the Kikuchi pattern showed that the crystallographic fault is a (011) twinning plane. The duration of annealing was found to have no significant effect on the dielectric permittivity, while the Q × f values increased two times with a prolongation of the annealing from 20 to 160 h. The highest Q × f value of 240 000 GHz was measured for Mg 3 B 2 O 6 ceramics with 5 wt% of Mg 2 B 2 O 5 . These ceramics consisted of 10 times larger grains than the Mg 3 B 2 O 6 ceramics without the added Mg 2 B 2 O 5 , which also showed high Q × f values of 200 000 GHz. The decrease of the amorphous phase during the annealing could be one of the reasons for this improvement of the Q × f values.