A new low-loss microwave dielectric ceramic for low temperature cofired ceramic applications
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Hong Wang Electronic Materials Research Laboratory, Key Laboratory of the Ministry of the Education, Xi’an Jiaotong University, Xi’an 710049, China (Received 9 January 2010; accepted 31 March 2010)
A new low sintering temperature microwave dielectric ceramic, Li2ZnTi3O8, was investigated. X-ray diffraction data show that Li2ZnTi3O8 has a cubic structure [P4332 ˚ , V ¼ 587.44 A ˚ 3, and Z ¼ 4 when the (212)] with lattice parameters a ¼ 8.37506 A sintering temperature is 1050 C. The Li2ZnTi3O8 ceramic exhibits good microwave dielectric properties with er about 26.2, Qf value about 62,000 GHz, and tf about 15 ppm/ C. The addition of BaCu(B2O5) can effectively lower the sintering temperature from 1050 to 900 C without degrading the microwave dielectric properties. Compatibility with Ag electrode indicates this material can be applied to low temperature cofired ceramic devices. Development of communication systems such as mobile systems requires the miniaturization of device size. Recently, low temperature cofired ceramic (LTCC) multilayer devices have been investigated to reduce the device size.1,2 As a metallic electrode, Ag has been widely used in LTCC technology because of its high conductivity and comparatively low cost. The melting temperature of Ag is low, about 961 C. Therefore, for the fabrication of the multilayer devices, it is important to develop microwave dielectric ceramics, which have a low sintering temperature and can be cofired with Ag. Unfortunately, although most of the well-known commercial microwave dielectric ceramics could have good microwave dielectric properties, they cannot be adopted as LTCC materials due to their high sintering temperatures. Therefore, how to reduce their sintering temperatures to below the melting point of the electrode conductor has aroused worldwide interest. Generally, addition of low-melting point oxides and glasses is the most often used method to lower the sintering temperature. In addition, considerable attention has been paid recently to the low-temperature firing ceramics possessing good microwave dielectric properties, such as TeO2-rich compounds,3,4 Bi2O3-rich compounds,5,6 MoO3-rich compounds,7,8 etc. Currently, the search for new kinds of low-temperature firing materials that have good microwave dielectric properties is still continuing. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0160 J. Mater. Res., Vol. 25, No. 7, Jul 2010
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Within the Li2O–ZnO–TiO2 system, the Li2ZnTi3O8 was first reported by Blasse9 and its crystal structure has also been studied.10,11 However, the microwave dielectric properties of Li2ZnTi3O8 ceramic have not been reported. In this study, the microwave dielectric properties, phase structure, and microstructure of Li2ZnTi3O8 were investigated. BaCu(B2O5) (BCB) has been reported as a good flux former to lower the sintering temperature for many materials.12–14 Therefore, to lower the sintering temperature to 900 C, a small a
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