The dielectric and electromechanical properties of 0.75Bi1/2Na1/2TiO3-0.25 SrTiO3 (25ST) as a function of temperature and frequency were studied. It is shown that the 25ST is a relaxor ferroelectric as evidenced by the temperature-dependent dielectric relaxations with an incipient piezoelectricity featured by the presence of a reversible electric-field-induced phase transformation at room temperature. The transition occurs on a broad electric field strength range depending on field amplitude and frequency. It is also accompanied by a huge strain that is attributed to repetitive poling and depoling originating due to the reversibility of the phase transition. The 25ST makes an attractive lead-free candidate for stack actuators as it presents a high normalized d33* of similar to 600pm/V at a low electric field of 4kV/mm for frequencies ranging from 0.1 up to 100Hz.