Significant displacement of calcium and barium ions in ferroelectric (Ba0.9Ca0.1)TiO3 revealed by x-ray fluorescence holography

Abstract

The x-ray fluorescence holography technique is applied to perovskite (Ba0.9Ca0.1)TiO3 ferroelectrics in order to investigate the local structures around the Ca and Ba ions at the A-site. While the A-site atomic images around the Ba ion can be well understood based on the BaTiO3 structure, those around the Ca ion are located at the closer positions to the emitter. Furthermore, the shape of the atomic image around the Ca ion is elongated in the radial direction. These features clearly show the local lattice contraction around the Ca ion and a significant displacement of the Ca ions from the ideal position. On the basis of the detailed analysis of the position and the shape of the atomic image around the Ca ion, it is found that the Ca ions are displaced by ∼0.36 Å in the ⟨111⟩ direction, and the surrounding Ba ions are displaced by ∼0.22 Å in the ⟨100⟩ direction. The present results indicate that the doped Ca ions activate the A-site polarization of this compound, which can lead to an enhancement of the ferroelectric and piezoelectric performances.

Observation of the Superstructure in Fe5–xGeTe2 by X-ray Fluorescence Holography

“…If the black spots were real atomic images, the Ge–Ge distance would be unfeasibly short. Furthermore, the displacement of the emitter atoms causes a change in the shape and the intensity of the surrounding atomic images but does not induce additional images . The reconstructed images typically suffer from conjugate images or artifacts, which are inherent to holographic techniques .…”

“…Furthermore, the displacement of the emitter atoms causes a change in the shape and the intensity of the surrounding atomic images but does not induce additional images. 25 The reconstructed images typically suffer from conjugate images or artifacts, which are inherent to holographic techniques. 22 This artifact can be suppressed by using multiple-energy holograms to reconstruct the atomic image.…”

KTaO3 Wafers Doped with Sr or La Cations for Modeling Water-Splitting Photocatalysts: 3D Atom Imaging around Doping Cations

“…Missing oxygen anions were observed in the reconstruction on lanthanum Lγ holograms of SrTiO 3 doped with La cations, 24 niobium Kα holograms of Pb(Fe 1/2 Nb 1/2 )O 3 , 25 and calcium Kα and barium Lγ holograms of (Ba 0.9 Ca 0.1 )TiO 3 . 26 The missing anions are interpreted with the limited X-ray scattering power of oxygen.…”

Local Structural Analysis around Solute-Element in Annealed Mg_99.2Zn_0.2Y_0.6 Alloy Using X-ray Fluorescence Holography

“…X-ray fluorescence holography (XFH) is a promising method to elucidate the arrangement of the solute-elements in Mg-TM-RE alloy. XFH can visualize three-dimensional atomic arrangement around a specific element [18][19][20] , and has been applied to various structural and functional materials [21][22][23][24][25][26][27][28][29][30] , including Mg85Zn6Y9 and Mg75Zn10Y15 alloys 31,32) . In particular, XFH is applicable to dilute systems 33) , and thus local structures around solute-elements in dilute Mg99.2Zn0.2Y0.6 alloy are expected to be clarified by this technique.…”