Phase transition, dielectric and piezoelectric properties of K0.5Na0.5NbO3–CaTi0.9Zr0.1O3 lead-free ceramics
2012
Lin, Dunmin | Kwok, Kin Wing
Lead-free (1 − x)K₀.₅Na₀.₅NbO₃–xCaTi₀.₉Zr₀.₁O₃ + 0.75 mol%MnO₂ piezoelectric ceramics have been prepared by an ordinary sintering technique and their phase transition, dielectric and piezoelectric properties have been studied. The results of X-ray diffraction show that CaTi₀.₉Zr₀.₁O₃ diffuse into K₀.₅Na₀.₅NbO₃ lattices to form a solid solution with a perovskite structure. After the addition of CaTi₀.₉Zr₀.₁O₃, both the cubic–tetragonal and tetragonal–orthorhombic phase transition temperatures decrease, and a relaxor behavior is induced. Coexistence of the orthorhombic and tetragonal phases is formed in the ceramics with 0.03 < x < 0.07 at room temperature. Owing to the higher number of possible polarization states resulting from the coexistence of the two phases, the piezoelectric properties of the ceramics are enhanced significantly. The ceramic with x = 0.05 exhibits the following optimum properties: d ₃₃ = 203 pC/N, k ₚ = 45.0%, and T C = 342 °C.
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