Synthesis of monoclinic CaSnSiO5 ceramics and their microwave dielectric properties
Highlights
► Monoclinic CaSnSiO5 ceramics were synthesized with a solid-state method. ► Pure CaSnSiO5 ceramics were synthesized by non-stoichiometric effect. ► High relative density and normal microstructure resulted in excellent properties.► Microwave properties of CaSnSiO5: εr=9.08, Q×f=61,000 GHz and τf=35 ppm/°C. ► CaSnSiO5 ceramics are promising millimeter-wave ceramic materials.
Introduction
Microwave dielectric ceramics have been widely used in the passive component [1], [2], local area network and intelligent transport systems. Microwave ceramic materials with low dielectric constant include Al2O3 [3], silicate [4], [5], MAl2O4 (M=Mg, Zn) [6], Mg4Nb2O9 system and so on. Nano-particles could improve the sintering behavior and microwave properties of ceramics [3].
Silicates, such as magnesium silicate (MgSiO3) [7], forsterite (Mg2SiO4) [8], [9], [10], zinc silicate (Zn2SiO4) [11], [12] and wollastonite (CaSiO3), [13] etc, have a low dielectric constant and high quality factor. MgSiO3 ceramics have excellent dielectric properties: εr=6.7, Q×f=121,200 GHz, τf=−17 ppm/°C [7], however they are easy to be powdered owing to the inevitable phase transformation. Microwave properties of Mg2SiO4 ceramics containing 0.5 wt.% LMZBS glass were: εr=7.3, Q×f=121,200 GHz [12]. (Mg0.4Zn0.6)2SiO4 ceramics indicate a good combination of microwave dielectric characteristics: εr=6.6, Q×f=95,650 GHz, and τf=−60 ppm/°C [9]. Mg2SiO4 and Zn2SiO4 ceramics have a strong processing sensitivity. CaSiO3 ceramics have a low densification and porous microstructure. In the present, LTCC materials were also investigated. Microwave properties of Li2MgSiO4 mixed with 1 wt.% LBS sintered at 925°C/2 h were: εr=5.5 and Q×f=114,000 at 8 GHz [14].
Even though numerous studies were conducted on silicates, dielectric properties of monoclinic CaSnSiO5 have not been investigated yet. In the present work, we reported the preparation, characterization, and microwave dielectric properties of CaSnSiO5 ceramics.
Section snippets
Experimental
CaSnxSiO5+δ (x=0.9, 0.95, 1.0, 1.05) ceramics were synthesized with solid-state synthesis method. CaCO3, nano-SnO2 particles (0.2 μm, Aladdin, Shanghai, China) and nano-SiO2 (7 nm, Degussa, Auckland, New Zealand) were mixed with a suitable molar ratio (nCa:nSn:nSi=1:x:1), and then milled with zirconia balls for 4 h on a planetary milling machine (QM - 3SP2, Nanjing, China). The mixtures were dried, and then calcined at 1100°C for 2 h. The calcined ceramic powders were re-milled for 4 h, dried, then
Results and discussion
XRD analysis: Fig. 1 shows the XRD patterns of CaSnxSiO5+δ sintered at 1525–1550 °C with varied compositions. From those patterns, one could find that trace orthorhombic SnO (JCPDS No. 13-0111) appeared in monoclinic CaSnSiO5 (ICSD No. 86-0928) ceramics at x=1.0, and the amount of SnO increased with increase sintering temperature. The pure monoclinic CaSnSiO5 phase (ICSD No. 86-0928) occurred when slightly non-stoichiometric compositions (x=0.9, 0.95 and 1.05) were employed. It could be ascribed
Conclusions
CaSnSiO5 ceramics were synthesized with a solid-state method. The molar ratio of Ca:Sn:Si=1:1.05:1 was employed to synthesize pure CaSnSiO5 ceramics by non-stoichiometric effect. High relative density, normal microstructure and large grain size resulted in excellent microwave dielectric properties. The CaSnSiO5 ceramics sintered at 1525 °C exhibited the following microwave dielectric properties: εr=9.08, Q×f=61,000 GHz and τf=35 ppm/°C.
Acknowledgments
This work was supported by The Guangdong-Hong Kong Technology Cooperation Funding Scheme (TCFS) under Grant 2010A090604002 and State Key Laboratory of New Ceramic and Fine Processing Tsinghua University.
References (17)
- et al.
Alloy Compd
(2010) - et al.
Mater Chem Phys
(2010) - et al.
Am Ceram Soc
(2007) - et al.
Am Ceram Soc
(2008) - et al.
Europ Ceram Soc
(2006) - et al.
Am Ceram Soc
(2009) - et al.
Science
(2001) - et al.
Appl Phys
(1996)et al.Mater Lett
(2005)et al.J Am Ceram Soc
(2007)