Structural and Electronic Parameters of Complex Niobates and Tantalates

Abstract

Abstract-Structural properties of anhydrous Nb5+ -niobates and Ta 5+ -tantalates have been evaluated with the help of classic polyhedra approach and atomic net model. X-ray photoelectron spectroscopy (XPS) is utilized as a powerful method to determine the binding energy (BE) of individual atoms in the crystal lattice. Chemical bonding effects are discussed for niobates and tantalates using the binding energy differences Δ Nb = (BE O 1s -BE Nb 3d 5/2 ) and Δ Ta = (BE O 1s -BE Ta 4f 7/2 ) as key parameters to relate structural and electronic properties of the compounds with pronounced dielectric nature. Photocatalytic materials such as Sr 2 Nb 2 O 7 , Ta 2 O 5 , LiTaO 3 , and Sr 2 Ta 2 O 7 are considered in particular.

X‐ray photoelectron spectroscopy study of neodymium niobate and tantalate precursors and thin films

“…%) in NdNbO 4 and NdTaO 4 powders are summarized in Tables and . The binding energy differences Δ(O―Nb) = B E (O 1s) − B E (Nb 3d 5/2 ) and Δ(O―Ta) = B E (O 1s) − B E (Ta 4f 7/2 ) were used as a suitable parameter to characterize average Nb―O bonding (322.9 eV) in NNO and Ta―O bonding in NTO (504.2 eV) . The same binding energy levels of Nb 3d 5/2 (206.7 eV) and Nb 3d 3/2 (209.4 eV) were found in TbNbO 4 and in the case of Ta 4f at 27.9 eV (4f 5/2 ) and 26.0 eV (4f 7/2 ) in YTaO 4 .…”

“…Neodymium niobate NdNbO 4 (NNO) and tantalate NdTaO 4 (NTO) ceramics and films possess mixed types of conduction processes, including protonic, ionic, and electronic conduction which is determined by fabrication conditions, and these materials are promising for sensors, solid fuel cell electrolytes, and high-temperature proton conductors. [1][2][3][4][5] One of the most detailed structural studies on LnMO 4 (Ln = rare earths; M = Nd, Ta), which covers lanthanide ions, were implemented by Siqueira et al [6][7][8][9] For these materials, several polymorph modifications are known. At room temperature, these compounds crystallize in the monoclinic M-and M′-fergusonite structures and transformed to the tetragonal T scheelite-type structure 3 depending on sol-gel synthesis conditions.…”