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A Chemical Route to BiNbO 4 Ceramics
Author(s) -
Shlyakhtin Oleg A.,
Oh YoungJei
Publication year - 2009
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/j.1744-7402.2008.02278.x
Subject(s) - materials science , eutectic system , sintering , ceramic , orthorhombic crystal system , crystallization , scanning electron microscope , phase (matter) , metastability , thermal decomposition , chemical engineering , dielectric , mineralogy , composite material , crystallography , microstructure , crystal structure , chemistry , physics , optoelectronics , organic chemistry , quantum mechanics , engineering
The liquid phase sintering of fine BiNbO 4 powders allows to obtain dense ceramics with excellent microwave dielectric properties (ɛ=44–46; Q × f =16,500–21,600 GHz) at T ≥700°C. The thermal decomposition of freeze‐dried precursors results in the crystallization of a metastable β′‐BiNbO 4 polymorph that transforms into a stable orthorhombic α‐modification at T ≥700°C. The dependence of sinterability on the powder synthesis temperature shows the maximum at 600°C, corresponding to the formation of crystalline BiNbO 4 powders with a grain size 80–100 nm. Sintering temperature reduction to 700°C prevents the deterioration of silver contacts during co‐firing with BiNbO 4 ceramics. In situ scanning electron microscopy observation of the morphological evolution during sintering shows that the intense shrinkage soon after the appearance of a CuO–V 2 O 5 eutectics‐based liquid phase is accompanied by complete transformation of the ensemble of primary BiNbO 4 particles.