Lead-free ceramics (1 - x)Bi0.5Na0.5TiO3-xSr(0.85)Bi(0.1)TiO(3) (BNT-xSBT, x = 0.4, 0.5, 0.6 and 0.7) were prepared by a solid-state reaction process. Coexistence of ferroelectric relaxation at low temperature and Maxwell-Wagner dielectric relaxation at high temperature was revealed for the first time in this system. Meanwhile, hysteresis-free P-E loops combined with a very high piezoelectric strain coefficient (d (33)) of 1658 pC/N concurrently with large electrostrictive coefficient Q = 0.287 m(4)C(-2) were achieved. The ferroelectric relaxor behavior and large electrostrictive strain might be linked to easy reorientation and reversal of ergodic PNRs and the combined effect of Bi off-center position and lone pair electrons.