Complex rare-earth substituted lead titanate piezoceramics

In this work we have investigated the properties of new compositions of Gd, Nd and a mixture of Gd+Nd -added Pb(Ti,Mn)O/sub 3/ ceramics, containing a few percent of Bi, to partially substitute the lead. The samples have been prepared starting from high purity oxides by solid-state reaction of oxide powders, within the sintering range 1100-1220/spl deg/C. Structural and morphological investigations were performed on poled samples. The use of X-ray diffraction together with microstructural examination by transmission electron microscopy has shown evidence for the formation of tetragonal perovskite phase. The domain structure and the lattice imperfection of the PT-type samples have been investigated by a high resolution transmission electron microscope (HRTEM). Samples with diameter 10 mm and thickness 1 mm have been employed for electrical characterization. Material coefficients have been investigated as a function of temperature. Dielectric constant and resistivity were measured with a four-wire probe also on unpoled samples in a wide temperature and frequency range.