This paper deals with the densification and phase transformation during pressureless sintering of Si3N4 with LiYO2 as the sintering additive. The dilatometric shrinkage data show that the first Li2O- rich liquid forms as low as 1250degreesC, resulting in a significant reduction of sintering temperature. On sintering at 1500degreesC the bulk density increases to more than 90% of the theoretical density with only minor phase transformation from alpha-Si3N4 to beta-Si3N4 taking place. At 1600degreesC the secondary phase has been completely converted into a glassy phase and total conversion of alpha-Si3N4 to beta-Si3N4 takes place. The grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. Li2O evaporates during sintering. Thus, the liquid phase is transient and the final material might have promising mechanical properties as well as promising high-temperature properties despite the low sintering temperature. The results show that the Li2O-Y2O3 system can provide very effective low-temperature sintering additives for silicon nitride.