Strain enhancement in lead-free Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 ceramics by CaZrO 3 substitution

Abstract

The effects of CaZrO₃ substitution on the crystal structure, electric field–induced strain, and piezoelectric properties of Bi_0.5(Na_0.78K_0.22)_0.5TiO₃ ceramics have been investigated. The CaZrO₃ substitution resulted in a transition from ferroelectric tetragonal to pseudocubic symmetry with relaxor characteristics, leading to degradations in the piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric coefficient d₃₃. However, the electric field–induced strain was significantly enhanced by the CaZrO₃-induced phase transition and reached a highest value of S _max /E _max = 617 pm/V when CaZrO₃ content reached 3 mol%. The result supports a prediction that a large strain at the ferroelectric–relaxor transition region can be observed when the tolerance factor of the Bi-perovskite is decreased by the substitution of ABO₃-type modifiers.