A ceramic composition which can be used as a sintering aid includes 1-2 mol % of magnesium oxide (MgO), 5-15 mol % of aluminum oxide (Al2O3), 25-40 mol % of silicon dioxide (SiO2), 40-55 mol % of calcium oxide (CaO), 0.1-8 mol % of ferric oxide (Fe2O3), 0.1-2 mol % of sulfur trioxide (SO3) and 0.1-2 mol % of titanium oxide (TiO2). Alternatively, the ceramic composition includes 1-8 mol % of MgO, 5-15 mol % of Al2O3, 25-40 mol % of SiO2, 40-55 mol % of CaO, 0.1-8 mol % of Fe2O3, 0.1-2 mol % of SO3 and 0.9-2 mol % of TiO2.