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Lead-free 0.96(K0.5Na0.5)NbO3-0.04LiTaO3 + x% MgO ceramics with x = 0.00, 0.25, 0.50, 0.75 and 1.00 were prepared by conventional solid-state sintering technique. The effects of MgO on the phase transitional behavior, microstructure, piezoelectric and dielectric properties were investigated. 0.96(K0.5Na0.5)NbO3-0.04LiTaO3 ceramics were chosen because of their high piezoelectric coefficient d33 and electromechanical coupling factor kp. These samples exhibit a polymorphic phase transition from orthorhombic to tetragonal symmetry near the room temperature, which is analogous to the morphtropic phase boundary (MPB). In order to further improve the piezoelectric and dielectric characteristics meanwhile decrease sintering temperature, alkaline earth element Mg had been doped in 0.96(K0.5Na0.5)NbO3-0.04LiTaO3 ceramics. Our results show that the doping of MgO could not only improve the sintering performance but also be effective on promoting the dielectric properties. [ABSTRACT FROM AUTHOR]

Abstract: Pb(Mg1/3Ta2/3)O3–Pb(Mn1/3Sb2/3)O3–Pb(Zr x Ti1−x )O3 quaternary piezoelectric ceramics with different compositions near the morphotropic phase boundary were synthesized using a conventional solid state reaction method. The phases, microstructures, ferroelectric, piezoelectric and dielectric properties of the system were investigated. A transition from rhombohedral to tetragonal phase was observed as the Zr/Ti ratio decreased. The P–E loops presented pinched shapes at low electric fields and the distortions disappeared at high electric fields. The dielectric study revealed a diffuse phase transition behavior in the ceramics. The optimal dielectric and piezoelectric properties ɛ r =817, d 33 =285pC/N, k p =0.55, T C =302°C, tan δ =0.4% and Q m =1600 of the ceramics were obtained at the composition of Zr/Ti=50/50. Vibration velocity at ΔT =20°C was found as high as 0.74m/s for this composition, which was almost 2.5 times as that of the commercial hard PZT ceramics. [ABSTRACT FROM AUTHOR]