Manganese-modified　niobate　ceramics　with　a　high　energy　density　were　constructed　by　pressureless　sintering　of　nanoprecursor　powders　derived　from　a　sol-gel　route.　The　room-temperature　orthorhombic-tetragonal　(O-T)　phase　boundary　of　the　(Na0.5K0.5)(0.94)Li0.06NbO3　(NKLN)　system　was　successfully　built　by　adding　Mn2+　ions　to　decrease　the　O-T　transition　temperature.　For　the　NKLN　+　2.0　mol-%　Mn2+　specimen,　an　optimal　transduction　coefficient　(d(33)xg(33))　value　as　high　as　9314x10(-15)　m(2)N(-1)　was　obtained;　this　value　is　comparable　to　reported　values　for　NKN　single　crystals,　and　thus,　this　material　shows　potential　application　in　new-generation　lead-free　piezoelectric　energy　harvesters.