Electronic structure of fluorescent lamp cathode surfaces: BaO/W(001)

Abstract

The BaO/W interaction is responsible for the emission properties of barium–oxide coated tungsten electrode coils in fluorescent lamps. The electronic structure of the BaO/W(001) interface is investigated by first-principles calculations within the local-density approximation of the density functional theory using the full-potential linearized augmented plane wave method. Results are presented for the total density of states (DOS), the atom- and orbital-resolved partial DOS and charge density distributions. Partial covalent character in the W–O and W–Ba bonding is shown. The main contribution to chemical bonding is caused by the tungsten d states and the adsorbate valence states, which interestingly also involve barium d states. This leads to a stabilization of the adsorbed configuration, with respect to cathode operation temperatures. The calculated work function is in agreement with experimental data.

Barium and oxygen interaction on the Ni(110) surface at low coverages studied by soft x-ray photoemission spectroscopy: Ba negative binding energy shifts and their correlation with Auger electron spectroscopy shifts

“…The most important difference is that Ba and BaO are directly adsorbed on a substrate, which is naturally expected to play an active role in the surface interactions. Ab initio calculations, performed by Almanstötter et al [23], for an ordered layer of BaO on W(100), showed significant W-O and W-Ba bonding with strong mixing of the Ba 5d orbitals (unoccupied in the free atom), in addition to the W 5d and O 2p ones. We do not know of any similar calculations for BaO on Ni, but XPS shifts from Ba to BaO on polycrystalline W [27] agree very well with our work down to the monolayer coverage, which was the minimum coverage studied in that work.…”

“…In order to gain knowledge on the structural, electronic and catalytic properties of AEMO thin films, the atomic and electronic structure should be investigated. Although, over the last decades, a number of studies have been performed related to BaO overlayers on several surfaces, both from the experimental [16][17][18][19][20][21][22] and the theoretical viewpoint [23][24][25], there are still obscure and controversial points concerning how the oxidation of the alkaline earth metal starts and develops on the surface. Among these points are the unusual negative binding energy shifts (NBESs) of some low core atomic levels (Ba 4d and 5p) after barium oxidation.…”

Auger electron spectroscopy and work function characterization of oxygen adsorption on Ba-covered Ni(110)

“…the extent of covalent bonding between the metal and oxygen). Recently, it was found through ab initio calculations that the bonding of BaO on W(100) involves strong hybridization of the W 5d and, intriguingly, the Ba 5d orbitals which are empty in the free atom, thus explaining the large WF decrease [11].…”

Solar assisted methanothermal reduction of barium oxide for the co‐production of barium and syngas

“…Electrodes of the fluorescent lamps are usually coated with the barium oxide to improve the release of electrons. 5 The refractive index and luster of the glass can be amplified with the use of barium carbonate. 6 Barium carbonate is also valuable for the decrease in the Xray leaks associated with the cathode ray tubes.…”

“…In addition to the usage mentioned above, the various compounds of Ba can be expended in several applications. Electrodes of the fluorescent lamps are usually coated with the barium oxide to improve the release of electrons 5 . The refractive index and luster of the glass can be amplified with the use of barium carbonate 6 .…”