New lead-free piezoelectric ceramics of ABO 3 perovskite type, Bi 1/2 Na 1/2 [Ti 1−x (Sb 1/2 Nb 1/2 ) x ]O 3 , were synthesized by conventional solid state reaction. The effect of the replacement of complex ions of (Sb 1/2 Nb 1/2 ) 4+ in the B cationic site on structural and electrical properties was investigated. The XRD analysis showed that all samples exhibited a single phase of perovskite structure. Piezoelectric and dielectric measurement revealed that the substitution of (Sb 1/2 Nb 1/2 ) 4+ ions lead to an increase in piezoelectric constant(d 33 ), electromechanical coupling factor(k t ), relative dielectric constant(ɛ r ),and loss tangent (tanδ), while excess of (Nb 1/2 Sb 1/2 ) 4+ ions results in a decrease in d 33 , k t , ɛ r , but an increase in tanδ. Temperature dependence of dielectric constant ɛ r measurement indicated these compounds were relaxor ferroelectric. At low frequency and high temperature, dielectric constant increased sharply attributed to the superparaelectric clusters after (Sb 1/2 Nb 1/2 ) 4+ ions substitution.