Nb 4d States Research Articles

Effect of Nb Doping on Fatigue in Lead Zirconate Titanate

We investigated the effect of Nb doping on fatigue in lead zirconate titanate (PZT), using the discrete variational Xα cluster method. From our calculation results, we conclude that Nb-doped PZT (PZTN) is less susceptible to fatigue than PZT because electrons released from oxygen vacancies occupy the Nb 4d states. This is consistent with our previous calculations; the effect of Nb doping on fatigue in PZT is the same as that of La doping on fatigue in PZT.

X-ray spectra and electronic structure of Li x NbO2 superconductor and other niobium oxide compounds

X-ray emission Nb\(L_{\beta _{2,15} } \) and OKα spectra and O1s total photoelectron yield spectra for superconductor Li0.71NbO2 and other niobium oxide compounds NbO, BaNb4O6, Ba2Nb5O9, BaNb5O8. LiNbO2, NbO2, LiNbO3 were investigated. It was found that in stoichiometric LiNbO2, niobium oxidation degree is 3+. Under the lithium deintercalation down to Li0.71NbO2 composition, the niobium ions oxidation degree increases up to 3.3+. As more electrons are supplied by Nb to fill the O2p band, the degree of O2p-Nb4d hybridization is increased. Using the full-potential linear muffin-tin orbital method, the self-consistent band structure calculations of Li x NbO2 (x=1.0; 0.7; 0.5) compounds were carried out. Agreement between partial Nb4d and O2p densities of states and corresponding X-ray spectra was observed. For thex=0.7; 0.5 the Fermi level is placed on the slope of sharp density of states peak formed mostly by the Nb4d states. With the decrease ofx thep-d hybridization becomes stronger, although remains well below the values typical for the high-temperature superconductors.

Detailed studies of the density of states of amorphous NbSi obtained by synchrotron radiation photoemission

Ultraviolet photoemission experiments using radiation from a synchrotron source have been used to study details of the valence bands of amorhous NbxSi1-x on either side of the metal-insulator transition. The alloys were prepared in situ by RF magnetron sputtering with surface and bulk characterization obtained by Auger electron spectroscopy and EXAFS respectively. The variation of the intensities of several features in the UV spectra with photon energy are due to the presence of resonant photoemission and Cooper minima in photoionization, and these effects can be used to identify the atomic origins of the partial densities of states in different parts of the valence bands. In the metallic phase such measurements show 'pure' Nb 4d states close to the Fermi edge, whereas for the insulating material there is no Fermi edge and little evidence for the Nb resonance.

Electron irradiation effects on oxidized Nb foil and NbO

Auger electron spectroscopy was used to study electron irradiation damage on niobium oxide. With the co-existence of O-2p and Nb-4d states in the valence band, the splitting of the MNN-type Auger transition peaks has been observed on Nb2O5 and oxidized Nb foil specimens. The results show that the surface of an electron-bombarded specimen becomes enriched with niobium due to irradiation-induced dissociation of the oxide and subsequent loss of oxygen. Supporting results obtained from electron stimulated desorption measurements, specimen coloration changes and layer-by-layer calculation of Auger intensity from an altered overlayer are also presented.