Probing structural disorder in (1−x)PbMg1/3Nb2/3O3–xPbTiO3 single crystals by x-ray photoelectron spectroscopy

Abstract

The (1−x)PbMg1/3Nb2/3O3–xPbTiO3 ((1−x)PMN –xPT) singlecrystals with x equal to 0, 0.22, 0.28, 0.32, 0.37, 0.47, 0.69 and 1 were studied by x-ray diffraction andx-ray photoelectron spectroscopy. X-ray diffraction results reveal that with increase ofTi content the crystal symmetry changes from pseudo-cubic, characteristic forPbMg1/3Nb2/3O3 (PMN), to rhombohedral, then to monoclinic at the vicinity of the morphotropicphase boundary (MPB) region and finally to tetragonal, specific forPbTiO3 (PT).High-resolution core level spectra of the Pb 4f, O 1s, Nb 3d and Ti 2p states show that the bulk of the(1−x)PMN –xPT crystals,except PbTiO3 where Pb2+ and Pb4+ were detected, is characterized by only one chemical state for each element. However, in thecase of the Pb and O spectra, apart from the main lines attributed to the lattice states, thesatellite lines related to the surface states were also observed. The evolution of the latticecomponents of all core level spectra points to regular concentration dependence of the fullwidth at half maximum (FWHM). With the rise of the Ti content the FWHMs increaseand reach maxima for the MPB region, then decrease and achieve the smallest valuesfor the pure PT. This characteristic FWHM behaviour points to disorder as anorigin of the core level line broadening and it is discussed within the frameworkof the random field model. The FWHM of the Bragg’s reflections show similarconcentration behaviour which confirms the existence of the highest structural disorder in(1−x)PMN –xPT system near the MPB.