The dielectric, ferroelectric and piezoelectric properties of strontium bismuth tantalate niobate, Sr1-xBi2+xTa2-yNbyO9 [SBTN10x(y)] ceramics were investigated. The samples were fabricated by a conventional ceramic fabrication technique. Curie temperature, Tc, increased with an increase in Nb concentration y, and Tc of SBTN2(y) showed two regions with different slopes that divided near y=1.0. The coercive field, Ec, of SBTN2(y) increased with the increase in y and the highest Ec of 90 kV/cm was obtained. SBTN2(0.6) and SBTN2(1.0) showed the highest coupling factor k33 of 0.17 in the SBTN2(x) system.