Lead-free　piezoelectric　ceramics　Sr2-xCaxNaNb5O15　+　y　wt%　MnO(2)have　been　prepared　by　the　conventional　solid　state　reaction　method.　Our　results　reveal　that　Ca2+　and　Mn　ions　have　entered　into　the　Sr2NaNb5O15　lattices　to　form　a　solid　solution　with　tungsten-bronze　structure.　The　substitution　of　Ca2+　induces　a　decrease　in　piezoelectric　coefficient　d(33),　electromechanical　coupling　factors　k(p)　and　k(t),　while,　the　addition　of　Mnions　decreases　the　sintering　temperature　and　effectively　promotes　the　densification　of　the　ceramics.　The　effect　of　substitution　of　Ca2+　and　Mn　ions　on　the　structure,　electrical　properties　and　diffused　phase　changing　were　investigated　systematically.　For　the　ceramic　with　x　=　0.05　and　y　=　0.5,　the　piezoelectric,　dielectric　and　ferroelectric　properties　become　optimum,　giving　a　piezoelectric　coefficient　d(33)　=　190　pC/N,　electromechanical　coupling　factors　k(p)　=　13.4%　and　k(t)　=　36.5%,　epsilon(r)　=　2123,　loss　tangent　tan　delta　=　0.038,　remanent　polarization　P-r　=　4.76　mu　C/cm(2),　coercive　field　E-c　=　12.68　kV/cm,　and　Curie　temperature　T-c　=　260　degrees　C.　(C)　2011　Elsevier　B.V.　All　rights　reserved.