X-ray diffraction and IR spectroscopic characterization of AgLnIII TiO4 oxides related to the K2NiF4 structural type

Abstract

Uma série de óxidos ternários do tipo AgLn III TiO 4 (com Ln = La, Nd, Sm, Eu, Gd, Dy, Y) foi preparada e os seus parâmetros de cela unitária foram determinados por difratometria de raios X. Esses compostos são relacionados com os do tipo estrutural K 2 NiF 4 , com os cátions Ag I e Ln III distribuídos de uma maneira ordenada no sub-retículo dos íons potássio. Os espectros de absorção no infravermelho desses materiais foram registrados e são discutidos com base nas suas peculiaridades estruturais e por comparação com as de óxidos similares. Os produtos apresentam uma relação estrutural e espectroscópica forte com os materiais de partida NaLn III TiO 4 .Ternary oxides of the type AgLn III TiO 4 (with Ln = La, Nd, Sm, Eu, Gd, Dy, Y) have been prepared and their unit cell parameters determined by X-ray powder diffractometry. They are related to the K 2 NiF 4 structural type, with the Ag I and Ln III cations distributed in an ordered way on the K-sub lattice. The infrared spectra of these materials were recorded and discussed on the basis of their structural peculiarities and by comparison with those of related oxides. They show a close relationship with the parent NaLn III TiO 4 materials.

Phase transformations during HLnTiO4 (Ln=La, Nd) thermolysis and photocatalytic activity of obtained compounds

“…3, 1) have three-band spectra with some minor splitting typical for cationic ordered layered oxides ALnTiO 4 [37][38][39]. The band around 400 cm À 1 can be assigned to the deformational modes of the TiO 6 octahedra, the middle energy band near 600 cm À 1 corresponds to the equatorial Ti-O stretching, while the high energy band near 800 cm À 1 can be ascribed to the stretching mode of Ti-O apical bond toward the protonic layer, similar as in NaLnTiO 4 compounds [38], but with significant shift to lower energies.…”

Layered Perovskite Compound NaLaTiO4 Modified by Nitrogen Doping as a Visible Light Active Photocatalyst for Water Splitting

“…However, clear off-centering of Ti in Ti­(O, N) 6 octahedrons is noticed in NaLaTiO 4– x N y (Figure b, inserted image). This has been attributed to a strong electrical field induced by charge imbalance on two sides of Ti­(O, N) 6 octahedrons, that is, Na + cations on one side and La 3+ cations on the other. − The ordering of Na and La in NaLaTiO 4– x N y has been the origin of its space group P 4/ nmm instead of I 4/ mmm although both Sr 2 TiO 4– x N y and NaLaTiO 4– x N y belong to the K 2 NiF 4 -type Ruddlesden–Popper compound . Such structure alterations have strong implications on changes of their electronic structures, as will be seen in the later section.…”