The two dissimilar dopants, Li2Si2O5 with small ionic sizes and inert Ag with a large atomic size were selected to understand the effects of activators on non-stoichiometrically activated sintering of Ca0.8Sr0.2TiO3 by doping with Ag, or co-doping with Ag and Li2Si2O5. The solubility limit of Ag+ in Ca0.8Sr0.2TiO 3 was ca. 7.0 mass%. The optimum sintering temperature was as low as 1353 K by co-doping of 5.0 mass% Ag and 0.5 mass% Li2Si 2O5. This firing temperature was lower than that of 1623 K using 5.0 mass% Ag, and 1473 K for 0.5 mass% Li2Si2O 5, respectively. The fracture strength of 363 MPa attained by co-doping was much high than the values of 291 and 292 MPa using 5.0 mass% Ag and 0.5 mass% Li2Si2O5, respectively.