Effect of Nb, Li doping on structure and piezoelectric properties of PZT type ceramics

The effect of niobium and lithium doping on the structure and piezoelectric properties of some samples with the following compositions PbZr0.051 Nb3Li)(x)Ti0.49-xO3, with 0.015 less than or equal to x less than or equal to 0.050, was investigated. The materials were prepared by the usual ceramic technique using high purity raw materials. Disc shaped samples of each composition were sintered at temperatures between 1200 and 1300 degrees C, for 4 h. The samples structure was determined by X-ray diffractometry and the piezoelectric properties were determined by means of resonance-antiresonance method, using a HP 4194A impedance gain phase analyser. A morphotropic phase boundary (MPB) with the optimum piezoelectric properties was found around the compositions with x=0020. The optimum values for relative dielectric constant epsilon(r), planar electromechanical coupling factor k(p), and mechanical quality, factor Q(m) of about 1700, 0.59 and 75, respectively, were found for these compositions. The lattice constants a and c of rhombohedral and tetragonal phases were determined by means of an X-ray CuK alpha diffractometer. The results are discussed in terms of the domain easy switching phenomena and high poling degree, brought about by the A-vacancies produced by the NbLi pairs doping. (C) 1999 Elsevier Science Limited. All rights reserved.