Oxygen states during thermal decomposition of Ag2O: XPS and UPS study

Abstract

Using photoemission XPS and UPS methods, we have studied the oxygen states in the silver metal lattice during the thermal decomposition Of Ag20. It has been shown that one half of the lattice oxygen inside subsurface layers of Ag~O is transformed to subsurface oxygen in metallic silver characterized by a quasimolecttlar structure. Thermal annealing up to 1000 K did not result in the removal of the residual subsurface oxygen.

Electronic Structure of Ag2Cu2O4. Evidence of Oxidized Silver and Copper and Internal Charge Delocalization

“…The case of the O 1s signal for AgO (not shown) agrees with previous studies . The metal−oxygen part corresponding to bonded oxygen is a single-component line despite the existence of both Ag I and Ag III and is slightly shifted toward lower binding energies and the disorder-induced part dominates over others giving an idea of the importance of disorder, or instability, in this material.…”

“…The spin−orbit splitting is 6.0 eV and the fwhm (full width at half-maximum) of the Ag 3d 5/2 line is 1.1 eV. Earlier XPS measurements performed on AgO − and Ag 7 O 8 NO 3 , assumed to exhibit both Ag I and Ag III oxidation states, show broader and slightly asymmetric Ag 3d single lines shifted toward lower binding energies in smaller extent and without resolved components. Our observations on AgO (not shown) agree with those reported earlier. − The main Ag 3d 5/2 peak is found at 367.4 eV and exhibits a fwhm of 1.7 eV, considerably larger than that for Ag 2 Cu 2 O 3 , which we ascribe to unresolved components from both oxidation states.…”

Modeling of oxygen adsorption on silver

“…In Ref [17] the formation of molecular oxygen species on silver after the introduction of oxygen at T = 873 K and P(O2) = 150 mbar was experimentally observed and connected with the adsorption -desorption process 02 (gas) -02 (orform). In our earlier study [16] we presented arguments proving that the a-form could not provide the surface coverage at temperatures above 500-600 K. The calculations reported here unambiguously prove that the or-form can be accumulated on the surface in noticeable (but not very high) amounts only at T < 500 -600 K. These calculations show once again that the a-form should rather be treated as a dissociation precursor, whereas the high-temperature molecular oxygen Z~02 has a completely different nature [15,16].…”

“…In our previous papers [15,16] it has been shown that thermally stable oxygen states have both atomic and molecular character. These data were obtained for polycrystalline silver surfaces where the input of high-index faces and block boundaries is relatively high.…”

Investigation of the role of Ag in Pr$_{1-x}$Ag$_x$MnO$_3$ manganites

“…Such various oxygen species (were labeled as O α , O β , O γ ,...) have different characteristics and some type of them may be stable and not desorbs up to above 900 K [18,19,20]. Also, it was shown that one half of the lattice oxygen inside subsurface layers of Ag 2 O is transformed to subsurface oxygen in metallic silver characterized by a quasimolecular structure, and thermal annealing up to 1000 K did not result in the removal of the residual subsurface oxygen [21]. As a result, we proposed that the enhancement of T C up to 130 K is due to the oxygen release from the metallic silver at high temperatures or may be due to the oxygen release from the molten silver when the sintering temperature exceeds the melting point of silver (960 • C).…”