Phase diagram of Bi 0.5 Na 0.5 TiO 3 -BaTiO 3 -K 0.5 Na 0.5 NbO 3 ternary system has been analyzed and ͑0.94− x͒BNT-0.06BT-xKNN ͑0.15Յ x Յ 0.30͒ ceramics have been prepared and investigated. Pseudocubic structures were confirmed by x-ray diffractions and its preliminary Rietveld refinements. P-E, S-E, and S-P 2 profiles ͑where P, E, and S denote polarization, electric field, and strain, respectively͒ indicate electrostrictive behavior of all ceramics. The compositions with x = 0.20 and 0.25 show pure electrostrictive characteristics. The dissipation energy, electrostrictive strain, and electrostrictive coefficient have been determined and compared with other lead-free and lead-containing electrostrictors. The electrostrictive coefficient can reach as high as 0.026 m 4 / C 2 , about 1.5 times of the value of traditional Pb-based electrostrictors. © 2010 American Institute of Physics. ͓doi:10.1063/1.3491839͔Both electrostrictive and piezoelectric ceramics are commercially used in electromechanical devices, such as actuators, space mirrors, etc. Electrostrictors have special advantages over piezoelectrics, because they do not require poling process and there is negligible hysteresis in strain-electric field ͑S-E͒ cycle, which is important for precision position control. [1][2][3] In electrostriction, the sign of the field-induced deformation is independent of the polarity of the field and is proportional to the square of the applied electric fieldwhere Q is the electrostrictive coefficient and P is polarization. 2 In recent years, a lot of attention has been paid to leadfree piezoelectric materials 4,5 but much less effort was devoted to high-performance lead-free electrostrictors. 6-9 One of the reasons might be due to the much smaller commercial market for high performance electrostrictors than for piezoelectric devices. Another reason might be due to the lack of public awareness on the fact that most of currently used electrostrictors are also lead based materials. With increasing pressure from environmental legislations, lead-free piezoelectric and electrostrictive materials are urgently in demand. Therefore, it is just as important to study lead-free electrostrictive materials as lead-free piezoelectric materials.Electrostriction is a general property of all dielectric materials but it is significantly large in ferroelectrics just above the Curie temperature ͑T c ͒, where an electric field can induce energetically unstable ferroelectric phase. In relaxor ferroelectrics, the electrostrictive strain can be kept at a relatively high level in a wide temperature range, because of the diffused phase transition. 2 If the phase transition temperature of a relaxor ferroelectrics is close to room temperature ͑RT͒, the electrostrictive effect can be very large at RT. Therefore, one may adjust the composition or dopants in lead-free relaxor ferroelectrics to produce pseudocubic/cubic crystal structure at RT, which might produce good lead-free electrostrictors. Recently reported electrostrictors, ͑Sr 1−y−x Na y Bi x ͒Ti...