Microstructure and dielectric properties of Li2CO3 doped 0.7(Ba,Sr)TiO3-0.3MgO ceramics for the low temperature sintering and microwave applications will be presented. In these days, low temperature sintering process has been widely spread out for the integrated electronic modules for the communication systems such as front-end modules, antenna modules, and switching modules. We have added Li2CO3 and MgO to (Ba,Sr)TiO3 material to reduce the sintering temperature and improve dielectric properties such as loss tangent, and frequency dispersion. in this paper, we have discussed the crystalline properties, dielectric properties, and the microstructures of Li2CO3 doped 0.7(Ba,Sr)TiO3-0.3MgO ceramics. No pyro phase was observed in the X-ray diffraction method. Very weak frequency dispersion (<0.7%) of dielectric permittivity was observed from the 1 kHz to 1 MHz range. We found that the grain size of BST is around 2 mu m, while the grain size of Li2CO3 dope 0.7BST-0.3MgO is around 4 mu m from the SEM analysis. (C) 2008 Elsevier B.V. All rights reserved.