Studies on ferroelectric perovskites and Bi-layered compounds using micro-Raman spectroscopy

This paper provides a review of a systematic micro-Raman scattering study on various lead- and barium-based ABO(3) perovskites (A = Pb, La, Ba, Sr, Ce, Gd, Nd and B = Ti, Zr), Aurivillius-type Bi-layered compounds (SrBi2Ta2O9, Bi4Ti3O12) and their solid solutions useful in a broad range of device applications. Various factors that influence the material properties such as particle size, stresses, stoichiometry, compositional homogeneity and their effects on phase transition were investigated. The processing conditions, A- and B-site substitution, size-dependent Raman spectra and the structure-property correlations are discussed in the bulk, thin film and nano-crystalline forms of these materials. A film thickness dependence stress study on lead titanate (PT) and lead zirconate titanate (PZT) films indicated that the nature of stress depends strongly on the lattice parameters of the film and substrate. The size effect was found to decrease the ferroelectric transition temperature in lead-based perovskite materials. Both ionic charge and radii induced changes in the Raman spectra of A- and B-site substituted perovskites and layered compounds were studied. A-site substitution in strontium bismuth tantalite (SBT) was found to induce a relatively linear variation of transition temperature compared with the B-site substituted SBT. Raman spectra of layered compounds and their solid solutions exhibited a strong dependence on dopants resulting in structural modifications. Copyright (C) 2002 John Wiley Sons, Ltd.