Exploring optoelectronic properties and mechanisms of layered ferroelectric K4Nb6O17 nanocrystalline films and nanolaminas

Abstract

Two-dimensional layered K4Nb6O17 (KN) was easily formed as a secondary phase caused by the volatilization of alkali metal ions, when preparing ferroelectric KxNa1−xNbO3 based ceramics and films. In this work, it was believed that KN film is with weak ferroelectricity and has a little effect on the ferroelectric properties of KxNa1−xNbO3 based films. Moreover, temperature dependent (77–500 K) dielectric functions of KN film have been firstly extracted by fitting ellipsometric spectra with the Adachi dielectric function model and a four-phase layered model. The high-frequency dielectric constant linearly increases and optical band gap slightly decreases with increasing the temperature. We also research its photoelectrochemical properties and its application in high-efficient light-induced H2 evolution. In addition, X-ray photoelectron spectroscopy, Raman scattering, temperature dependent transmittance and infrared reflectance spectra, and first-principles calculation were conjointly performed to further reveal the intrinsic optoelectronic features and relevant mechanisms of KN.

Self-Assembled Interwoven Nanohierarchitectures of NaNbO3 and NaNb1–xTaxO3 (0.05 ≤ x ≤ 0.20): Synthesis, Structural Characterization, Photocatalytic Applications, and Dielectric Properties

“…Figure 6 c represents the high-resolution XPS spectra of O 1s, which is centered at a binding energy equal to 529 eV confirming the −2 oxidation state of O. 41 The peak corresponding to O 1s originates due to −Nb–O in pure NaNbO 3 or due to −Ta–O present in Ta-doped NaNbO 3 samples. Figure 6 d shows the high-resolution XPS spectra of Nb element present in the synthesized photocatalysts.…”

Development of Cuboidal KNbO3@α-Fe2O3 Hybrid Nanostructures for Improved Photocatalytic and Photoelectrocatalytic Applications

“…Figure b shows the high-resolution XPS spectra of Nb 3d present in pure KNbO 3 and KNbO 3 /α-Fe 2 O 3 heterostructure. The gap between the two Nb peaks at 206.47 and 209.22 eV is 3 eV, which may be associated with the +5 oxidation state of Nb Figure c shows the high-resolution XPS spectra of K 1+ 2p present in pure KNbO 3 and KNbO 3 /α-Fe 2 O 3 heterostructure, which demonstrates that K is present in +1 oxidation state in both pure and heterostructured KNbO 3 .…”

“…The gap between the two Nb peaks at 206.47 and 209.22 eV is 3 eV, which may be associated with the +5 oxidation state of Nb. 53 Figure 5c shows the high-resolution XPS spectra of K 1+ 2p present in pure KNbO 3 and KNbO 3 /α-Fe 2 O 3 heterostructure, which demonstrates that K is present in +1 oxidation state in both pure and heterostructured KNbO 3 . The peaks at 291.2 and 294.04 eV correspond to K 2p 3/2 and K 2p 1/2 states.…”

Controllable interlayer space effects of layered potassium triniobate nanoflakes on enhanced pH dependent adsorption-photocatalysis behaviors

“…It can be seen that KN1 shows sharp and strong Raman bands around 901 cm −1 . A detailed discussion of the Raman spectra for KN1 can be found in our previous study 3 . Theoretically, KN has an orthorhombic structure with an Amam space group.…”

“…With the growing demands for solving environmental problems, low dimensional semiconductor materials with multifunctional applications have raised considerable research interest 1 , 2 . Two-dimensional (2D) layered transition metal oxides should be unnegligible due to their charming features, such as the excellent thermal stability under an oxygen atmosphere 3 , 4 . As a typical case, layered KNb 3 O 8 (KN) possesses unique interlayer regions, which makes it of great interest for applications in environmental purification, non-linear optics, energy conversion, etc 5 – 9 .…”