Effect of TiO2 Doping on the Structure and Microwave Dielectric Properties of Cordierite Ceramics. Issue 6 (20th March 2015)

• Record Type: Journal Article
• Authors: Wu, Song; Song, Kaixin; Liu, Peng; Lin, Huixing; Zhang, Fangfang; Zheng, Peng; Qin, Huibin; Alford, N.
• Is Part Of: Journal of the American Ceramic Society. Volume 98:Issue 6(2015)
• Page Start: 1842
• Page End: 1847
• Publication Date: 2015-03-20
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.13549
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace13549-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The (1−<italic>x</italic>)Mg<sub>2</sub>Al<sub>4</sub>Si<sub>5</sub>O<sub>18</sub>–<italic>x</italic>TiO<sub>2</sub> |(1−<italic>x</italic>)MAS‐<italic>x</italic>T| (0 ≤ <italic>x</italic> ≤ 0.35) cordierite ceramics are fabricated by solid‐state reaction method for obtaining near‐zero temperature coefficient of resonant frequency (τ<sub>f</sub>). The XRD and SEM results show that (1−<italic>x</italic>)MAS‐<italic>x</italic>T (0 ≤ <italic>x</italic> ≤ 0.10) ceramics exhibit single cordierite solid solution, whereas as 0.15 ≤ <italic>x</italic> ≤ 0.35, present composite phases of Mg<sub>2</sub>Al<sub>4</sub>Si<sub>5</sub>O<sub>18</sub> solution and TiO<sub>2</sub>. Rietveld refinements of XRD data suggest that the [(Si<sub>4</sub>Al<sub>2</sub>)O<sub>18</sub>] hexagonal shape in cordierite structure happens to alternate change from nonsymmetrical hexagonal rings to almost centrosymmetrical equilateral rings as <italic>x</italic> increases to 0.10 comparing to that of <italic>x</italic> = 0. As Ti<sup>4+</sup> ions squeeze into the [(Si<sub>4</sub>Al<sub>2</sub>)O<sub>18</sub>] rings structure, the orientation and shapes of the rings begin to rotate and expand from initial state of [1–20] (<italic>x</italic> = 0) to near [210] direction (<italic>x</italic> = 0.10), and then continue to expand toward close to [110] direction (<italic>x</italic> = 0.25). Due to centrosymmetry adjustment of [(Si<sub>4</sub>Al<sub>2</sub>)O<sub>18</sub>] hexagonal rings and of other microstructure factors improvement, the (1−<italic>x</italic>)MAS‐xT (<italic>x</italic> = 0.10) cordierite solution achieves optimum quality factor <italic>Q</italic><sub>f</sub>: ε<sub>r</sub> = 6.3, <italic>Q</italic><sub>f</sub> = 55 400 GHz (17.6 GHz), τ<sub>f</sub> = −21 ppm/°C. The (1−<italic>x</italic>)MAS‐<italic>x</italic>T (<italic>x</italic> = 0.25) composites obtain a near‐zero temperature coefficient of resonance frequency: ε<sub>r</sub> = 6.8, <italic>Q</italic><sub>f</sub> = 37 800 GHz (18.4 GHz), τ<sub>f</sub> = −0.2 ppm/°C.</p> </abstract>