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Effect of TiO 2 Doping on the Structure and Microwave Dielectric Properties of Cordierite Ceramics
Author(s) -
Wu Song,
Song Kaixin,
Liu Peng,
Lin Huixing,
Zhang Fangfang,
Zheng Peng,
Qin Huibin
Publication year - 2015
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/jace.13549
Subject(s) - cordierite , materials science , ceramic , temperature coefficient , microstructure , rietveld refinement , hexagonal crystal system , doping , crystallography , solid solution , mineralogy , analytical chemistry (journal) , crystal structure , chemistry , composite material , metallurgy , optoelectronics , chromatography
The (1− x )Mg 2 Al 4 Si 5 O 18 – x TiO 2 |(1− x ) MAS ‐ x T| (0 ≤ x ≤ 0.35) cordierite ceramics are fabricated by solid‐state reaction method for obtaining near‐zero temperature coefficient of resonant frequency (τ f ). The XRD and SEM results show that (1− x ) MAS ‐ x T (0 ≤ x ≤ 0.10) ceramics exhibit single cordierite solid solution, whereas as 0.15 ≤ x ≤ 0.35, present composite phases of Mg 2 Al 4 Si 5 O 18 solution and TiO 2 . Rietveld refinements of XRD data suggest that the [(Si 4 Al 2 )O 18 ] hexagonal shape in cordierite structure happens to alternate change from nonsymmetrical hexagonal rings to almost centrosymmetrical equilateral rings as x increases to 0.10 comparing to that of x = 0. As Ti 4+ ions squeeze into the [(Si 4 Al 2 )O 18 ] rings structure, the orientation and shapes of the rings begin to rotate and expand from initial state of [1–20] ( x = 0) to near [210] direction ( x = 0.10), and then continue to expand toward close to [110] direction ( x = 0.25). Due to centrosymmetry adjustment of [(Si 4 Al 2 )O 18 ] hexagonal rings and of other microstructure factors improvement, the (1− x ) MAS ‐ xT ( x = 0.10) cordierite solution achieves optimum quality factor Q f : ε r = 6.3, Q f = 55 400 GHz (17.6 GHz), τ f = −21 ppm/°C. The (1− x ) MAS ‐ x T ( x = 0.25) composites obtain a near‐zero temperature coefficient of resonance frequency: ε r = 6.8, Q f = 37 800 GHz (18.4 GHz), τ f = −0.2 ppm/°C.