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 tec hnique using high purity raw materials. Disc shaped samples of each composi tion were sintered at temperatures between 1200 and 1300 degrees C, for 4 h . The samples structure was determined by X-ray diffractometry and the piez oelectric properties were determined by means of resonance-antiresonance me thod, using a HP 4194A impedance gain phase analyser. A morphotropic phase boundary (MPB) with the optimum piezoelectric properties was found around t he compositions with x=0020. The optimum values for relative dielectric con stant epsilon(r), planar electromechanical coupling factor k(p), and mechan ical quality, factor Q(m) of about 1700, 0.59 and 75, respectively, were fo und for these compositions. The lattice constants a and c of rhombohedral a nd tetragonal phases were determined by means of an X-ray CuK alpha diffrac tometer. The results are discussed in terms of the domain easy switching ph enomena and high poling degree, brought about by the A-vacancies produced b y the NbLi pairs doping. (C) 1999 Elsevier Science Limited. All rights rese rved.