화학공학소재연구정보센터
Journal of the American Ceramic Society, Vol.102, No.5, 2675-2683, 2019
Design on improving piezoelectric strain and temperature stability of KNN-based ceramics
Lead-free 0.99(0.96K(0.46)Na(0.54)Nb(1-x)Ta(x)O(3)-0.04Bi(0.5)(Na0.82K0.18)(0.5)ZrO3)-0.01CaZrO(3) (0.99(0.96KNNTax-0.04BNZ)-0.01CZ) ceramics were prepared by a solid-state sintering method. Ta2O5 doped in the 0.99(0.96KNNTax-0.04BNZ)-0.01CZ ceramics results in a phase structure transition from the orthorhombic (O)/tetragonal (T) phase to the rhombohedral (R)/T phase. The Ta2O5 dopant induces a decrease in the average grain size from similar to 1.70 to similar to 0.69 mu m. At x = 0.02 and 0.04, the ceramics have a high reverse piezoelectric coefficient (similar to 500 pm/V under 25 kV/cm). The ceramics with x = 0.04 show an optimal level of unipolar strain, reaching 0.17% under 35 kV/cm at room temperature, and their field-induced strain varies <10% in the temperature range from 25 to 135 degrees C. The presence of the O phase in the polymorphic phase boundary (PPB) improves the temperature stability the reverse piezoelectric coefficient (d33*). Obtaining KNN-based ceramics with good piezoelectric properties and weak temperature sensitivity by designing a R/O/T phase boundary and controlling the average grain size to the submicrometer level is highly feasible.