Bi 0.5 (Na 1−x−y K x Ag y ) 0.5 TiO 3 piezoelectric ceramics were prepared by conventional ceramic processes. X-ray diffraction patterns show a pure perovskite structure, indicating that the K + and Ag + ions substitute for the Na + ions in Bi 0.5 Na 0.5 TiO 3 . The temperature dependence of the dielectric constant and dissipation factor shows all ceramics to experience two phase transitions: from ferroelectric to anti-ferroelectric and from anti-ferroelectric to paraelectric. The transition temperature from ferroelectric to anti-ferroelectric and the temperature at which the dielectric constant reaches its maximum value decrease with the increase of K + amount. At room temperature, the ceramics containing 17.5–20mol% K + and 2mol% Ag + exhibit high piezoelectric constant (d 33 =180pC/N) and high electromechanical coupling factor (k p =35%).