Piezoelectric properties of PbHfO ₃-PbTiO ₃-Pb(Mg _1/3Nb _2/3)O ₃ ternary ceramics

(1 - x)Pb(Hf _1-yTi _y)O ₃-x Pb(Mg _1/3Nb _2/3)O ₃ (x = 0.1 ∼ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two-step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ∼ 0.22, were confirmed using X-ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf _0.445Ti _0.555)O ₃-0.2Pb(Mg _1/3Nb _2/3)O ₃, with dielectric permittivity ε _r, piezoelectric coefficient d ₃₃, planar electromechanical coupling k _p and Curie temperature T _C being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved T _C, showing a potential for applications at elevated temperature.