Effects of Ti on dielectric and piezoelectric properties of (Pb0.985La0.01)1+y(Nb1−yTiy)2O6 ceramics

Piezoelectric ceramics (Pb0.985La0.01)1+y(Nb1−yTiy)2O6 (0 ⩽ y ⩽ 0.1) (PLNT) were fabricated by a conventional solid-state reaction method. The crystal structure and microstructures of specimens were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). All PLNT ceramics sintered at temperatures from 1250 °C to 1290 °C are shown to be a single orthorhombic phase. The formation of orthorhombic phase is promoted by excess PbO existed in the Ti-bearing samples during calcination processing. The increasing of the tolerance factor due to substitution of Ti4+ for Nb5+ is also responsible for the stability of orthorhombic phase. The high density of ceramics (relative density >95%) with the equiaxed grains and a minor porosity have been obtained. The measurement of dielectric and piezoelectric properties of PLNT ceramics reveals that Ti reduces the dielectric loss (tan δ) and dielectric constant (εr) of PLNT ceramics, and enhances the piezoelectric constant (d33) and Curie temperature (Tc). The optimum component with y = 0.075 possesses the excellent electrical properties: εr = 182, tan δ = 0.0018, d33 = 84 pC/N and Tc = 564 °C.