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Glass‐Free LTCC Microwave Ceramic‐( La 0.5 Na 0.5 ) 1− x ( Li 0.5 Nd 0.5 ) x WO 4
Author(s) -
Bian Jian Jiang,
Wang Liang
Publication year - 2011
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.1551-2916.2011.04757.x
Subject(s) - ceramic , microstructure , materials science , analytical chemistry (journal) , dielectric , scanning electron microscope , scheelite , impurity , mineralogy , microwave , chemistry , metallurgy , composite material , tungsten , chromatography , optoelectronics , organic chemistry , quantum mechanics , physics
Ceramics ( La 0.5 Na 0.5 ) 1− x ( Nd 0.5 Li 0.5 ) x WO 4 (0.1 ≤ x ≤ 0.7) have been successfully designed as promising dielectric materials for LTCC applications. The structure and microstructure of the compounds were investigated by X‐ray powder diffraction ( XRD ) and scanning electron microscopy ( SEM ) method. The microwave dielectric properties of the ceramics were studied with a network analyzer at the frequency of about 10–14 GHz. Continuous solid solutions ( La 0.5 Na 0.5 ) 1− x ( Nd 0.5 Li 0.5 ) x WO 4 (0.1 ≤ x ≤ 0.7) were formed as expected in the whole composition range. They could be sintered into dense ceramic (~96% theoretical density) at 800°C/2 h. All samples exhibit single Scheelite structure (I4 1 /a) phase. The dielectric constant increased, whereas the Q × f value decreased continuously, with the increase of x . The τ f value changed from negative to positive with the increase of x , and near zero value of −1.4 ppm/°C could be obtained at x = 0.3 composition. Combined excellent microwave dielectric properties with ε r = 12.7, Q × f = 23 518 GHz and τ f = −1.4 ppm/°C could be obtained when sintered at 800°C/2 h. The chemical compatibility of (La 0.5 Na 0.5 ) 0.7 (Nd 0.5 Li 0.5 ) 0.3 WO 4 ceramic with silver ( Ag ) powders was also investigated. Some Ag substituted for Li and formed Li 2 WO 4 impurity phase, although isolated Ag still existed in the co‐fired specimen (800°C/2 h).