An addition of just 0.4 wt% Li2O to (Ba,.,Sr,.,)TiO3 powder was able to reduce the sintering temperature to less than or equal to900degreesC and produce ceramics with a relative density of 97%. Small amounts of two secondary phases were formed during this process: Li2TiO3 and Ba2TiO4. The addition of Li2O depresses the ferroelectric character of the (Ba0.6Sr0.4)TiO3 and, as a result, reduces the permittivity, improves the temperature coefficient of permittivity, and reduces the dielectric losses. The tunability shows no significant variation with Li2O concentration and remains between 16.5% and 13.5%. A lowtemperature sintering mechanism was proposed. The mechanism involves the intermediate formation of BaCO3, its melting and the incorporation of Li+ into the BST. The sintering mechanism can be characterized as reactive liquid-phase sintering.