Estudo das propriedades físicas do composto NixPb1-xTiO3: compósito versus solução sólida

Abstract

In this work a physical properties study of the samples series NixPb1-xTiO3 will be presented using several experimental techniques, with emphasis on Raman spectroscopy and X-ray diffraction. For these samples, Raman scattering is a powerful characterization technique once the E (1TO), smallest wavenumber of PbTiO3, so-called "soft mode", is a very sensitive probe for small lowest structural local symmetry changes. The samples with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by the solid state reaction method using oxides, PbO, NiO and TiO2, with 99% purity degree. The precursor oxides were milled in a high energy vibratory mill and thermal treated at temperatures ranging from 925 K to 1375 K. The atomic substitution for ions with a very different crystal radius is one of the convenient routes for the generation of composites on ATiO3-type materials. Another possible route is to use materials which the end compositions have different crystallographic structures. As materials in the form of a solid solution or composite may present different properties, their study becomes a relevant theme. Lead titanate, PbTiO3, is an important ferroelectric material which has tetragonal structure at room conditions and whose several physical properties such as structural, vibrational, thermal, dielectric, etc. are well known in the literature. On the other hand, nickel titanate, NiTiO3, has rhombohedral ilmenite structure at room conditions and is employed manly as a dry lubricant due to its high hardness or as a pigment. Moreover, it presents magnetic ordering, being hence a possible candidate to be used in new materials with magneto-electric properties. PbTiO3 and NiTiO3 are both ATiO3-type materials, so it can be expected that their combination may results in very interesting material for technological applications such as the reduction of the high loss and dielectric constant of PbTiO3, a request for devices working in the microwave frequencies.