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Structural Evolution and Microwave Dielectric Properties of Li (3−3x) M 4x Nb (1−x) O 4 (M=Mg,Zn; 0≤x≤0.9)
Author(s) -
Bian Jianjiang,
Liang Zhu,
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.1551-2916.2010.04244.x
Subject(s) - microwave , dielectric , materials science , analytical chemistry (journal) , crystallography , mineralogy , chemistry , optoelectronics , physics , organic chemistry , quantum mechanics
Structural evolution of Li (3−3 x ) M 4 x Nb (1− x ) O 4 (M=Mg,Zn; 0≤ x ≤0.9) and microwave dielectric properties of Li (3−3 x ) Mg 4 x Nb (1− x ) O 4 have been studied by X‐ray diffraction, scanning electron microscopy, Raman spectra, infrared reflectivity (IR) fitting, and microwave resonant measurement in this work. The crystal symmetry changed from the ordered cubic Li 3 NbO 4 ( I ‐43 m , x =0) into disordered cubic phase ( Fm 3 m ) when 0.01≤ x <1/3 for the Mg‐doped samples. An intermediate compound of Li 3 Mg 2 NbO 6 (SG: Fddd ) with orthorhombic structure formed at x =1/3 composition. MgO secondary phase appeared in addition to Li 3 Mg 2 NbO 6 phase in the x >1/3 compositions, and its content increased with the further increase of x . Short‐range cation ordering was confirmed to be present in the cubic phase by Raman analysis. Mixture of Li 3 NbO 4 and ZnO phases was observed in the whole composition range for the ZnO‐added samples. For the Mg‐doped samples, the dielectric constant increased slightly with x increasing up to x =1/3 and decreased with the further increase of x . The Q × f value increased greatly with the increasing x and saturated within the composition range of 0.1≤ x <1/3. Further increasing x resulted in a decrease in Q × f value. All samples exhibited negative τ f value. Minimum τ f value of −22 ppm/°C was obtained at x =1/3. The IR reflection spectra of the x =0, 0.2, and 1/3 samples were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. The calculated dielectric constants were in agreement with the experimental ones, whereas, the calculated Q × f values showed a reverse varying trend compared with the experimental data.