Synthesis and properties of Bi0.5(Na1−x−yKxAgy)0.5TiO3 lead-free piezoelectric ceramics

Abstract 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 17.5–20 mol% K + and 2 mol% Ag + exhibit high piezoelectric constant ( d 33 = 180 pC/N) and high electromechanical coupling factor ( k p = 35%).