Investigation of Ternary System PbHfO3-PbTiO3-Pb(Mg1/3Nb2/3)O3 with Morphotropic Phase Boundary Compositions

Ternary system, (1-x)Pb(Hf1-yTiy)O3xPb(Mg1/3Nb2/3)O3 (x similar to=similar to 00.5, y similar to=similar to 0.450.70) was prepared using two-step precursor method. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the ceramics near morphotropic phase boundary (MPB) have been investigated systematically. On the basis of the results of X-ray powder diffraction and dielectric-temperature measurement, the MPB region and isothermal map of Curie temperature (TC) for the ternary system were obtained. The optimum piezoelectric and electromechanical properties were achieved in the MPB composition 0.8Pb(Hf0.445Ti0.555)O30.2Pb(Mg1/3Nb2/3)O3, with piezoelectric d33 being on the order of 680 similar to pC/N, while the maximum high-field piezoelectric d33* of 780 similar to pm/V was observed for 0.82Pb(Hf0.445Ti0.555)O30.18Pb(Mg1/3Nb2/3)O3 with tetragonal composition, due to the high extrinsic contribution induced by domain wall motion. In addition, the fracture toughness KIC and flexural strength sf were measured and found to be 1.2 similar to MPa center dot m1/2 and 71.4 similar to MPa, respectively, comparable to PZT-based ceramics.