XAS and XRD Structural Characterization of Lanthanum-Modified PbTiO3 Ceramic Materials

For the first time combined X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) experiments were carried out to probe the short- and long-range order in lanthanum-modified PbTiO3 ceramic materials (Pb1 - x La x TiO3) for x ranging from 0 to 30 atom % of La. XRD results show that a tetragonal structure fitted well to all samples, except to the one with 30 atom % of La for which XRD results highlighted a cubic unit cell. XRD refinements also confirmed the existence of only A-site vacancies. X-ray absorption near edge spectroscopy (XANES) measurements indicate that the local structure around Ti atoms has a different compositional dependence from the one obtained from XRD, mainly for the sample with 30 atom % of La. According to XANES data, for the sample with 30 atom % of La, a local distortion around Ti atoms persist. The analysis of extended X-ray absorption fine structure (EXAFS) spectra shows a decrease in the local disorder around Ti atoms as the content of La increases. Structural details, in terms of short and long-range order, are presented and the correlation between the XRD and XANES/EXAFS data is discussed.