January 26, 2010

Volume 93 Issue 1, Pages 147 – 154

Tony Joseph, Mailadil T. Sebastian
Published Online: Oct 29 2009 6:04PM
DOI: 10.1111/j.1551-2916.2009.03370.x

ABSTRACT
The (Sr1-xAx)2(Zn1-xBx)Si2O7 ceramics (A=Ca, Ba and B=Co, Mg, Mn, Ni) were prepared by the conventional solid-state ceramic route and their structure and microwave dielectric properties were investigated. The majority of the compositions have an akermanite-type structure except for A/B=Ba/Zn and Sr/Ni. A structural change is observed from tetragonal to monoclinic with the increase in Ba2+ content at the Ca-site. When Zn2+ was completely replaced by Ni2+, a mixture of SrSiO3 and NiO phases resulted instead of the solid solution Sr2NiSi2O7. The variation of cell parameters and cell volumes of (Sr1-xAx)2(Zn1-xBx)Si2O7 was studied for various compositions (x) in the range 0-1. Excellent dielectric properties (ɛr=8.4, Qu×f=105 000 GHz (at 12.628 GHz) and τf=-51.5 ppm/°C) were obtained for the composition Sr2ZnSi2O7 when sintered at 1475°C/2 h. Addition of 2 wt% of SrTiO3 to Sr2ZnSi2O7 decreased the τf value to -13 ppm/°C with ɛr=8.8, Qu×f=60 000 GHz (at 12.585 GHz). Thus, a composite of Sr2ZnSi2O7 and SrTiO3 is a possible material for millimeter-wave communication systems and as microwave substrates.

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