The Sm2 Si2O7 ceramics were synthesized by solid-state ceramic route. The calcination and sintering temperature of Sm2 Si2 O7 were optimized for the best properties. The crystal structure and microstructure of the ceramic were studied by X-ray diffraction and scanning electron microscopic methods. The low frequency dielectric properties were studied at 1MHz. The dielectric properties of the ceramic were measured in the microwave frequency range by the cavity perturbation method. Sm2 Si2O7 has εr =12.5, tan δ=8 × 10-4, and τε =+63ppm/°C at 1MHz and a relative permittivity of 10 and tan δ of6 × 10-3 in the microwave frequency range. The effect of addition of various low loss glasses such as 50ZnO-50B2O3 (ZB), 60ZnO-30B2O3 -10SiO2 (ZBS), 27B2 O3 -35Bi2O3 -6SiO2 -32ZnO (BBSZ), 22.2MgO-22.2Al2O3 -55.5SiO2 (MAS), 35.1Li2 O-31.7B2 O3 -33.2SiO2 (LBS) and 20Li2 O-20MgO-20ZnO-20B2O3 -20SiO2 (LMZBS) on the microwave dielectric properties of Sm2 Si2 O7 was also investigated. It was found that the addition of 15wt% LBS glass reduced the sintering temperature from 1375°C to 975°C with εr = 9.89 and tan δ = 0.024. Fifteen weight percent LMZBS glass ceramic decreased the sintering temperature to 950°C with εr = 9.09 and tan δ = 0.009. The results show that Sm2 Si2O7 mixed with suitable amounts of selected glasses is a promising material for microwave substrate applications. © 2009 The American Ceramic Society.