It is demonstrated that the use of similar to 0.9 mol% Li2CO3 (LC) as a sintering aid for Sr, K, Nb modified Pb(Zr1-x,Ti-x)O-3 (PZT) ceramics is effective only in the presence of excess PbO (similar to 2 mol%). It is shown that LC and PbO react to form the compound, Li2PbO3 (LPO) which has a melting temperature of similar to 836 degrees C. Using dilatometry, we were able to correlate shrinkage during heating of a green ceramic to the melting of the LPO. Consequently, complete densification and sizeable grain growth are achieved by solution-precipitation of the ceramic through the liquid phase. Importantly, sintering is not particularly effective with such small additions of either LC or PbO alone. In confirmation of this model, the LPO compound was presynthesized and used as the only sintering aid in the same PZT composition. The densification behavior of this mixture compared well with the case of separate additions.