PRODUCTION OF OXYGEN VACANCIES BY ELASTIC COLLISIONS IN ALKALINE EARTH OXIDES

1973 ◽  
Vol 34 (C9) ◽  
pp. C9-515-C9-518 ◽  
Author(s):  
A. E. HUGHES
Keyword(s):  
Alkaline Earth ◽  
Oxygen Vacancies ◽  
Elastic Collisions

Methanation of CO2 over Ni/Al2O3 modified with alkaline earth metals: Impacts of oxygen vacancies on catalytic activity

2019 ◽  
Vol 44 (16) ◽  
pp. 8197-8213 ◽  
Author(s):  
Chuanfei Liang ◽  
Xun Hu ◽  
Tao Wei ◽  
Peng Jia ◽  
Zhanming Zhang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Alkaline Earth ◽  
Oxygen Vacancies ◽  
Alkaline Earth Metals

The Effect of Hydrogen on the Charge States of Oxygen Vacancies in Thermochemically Reduced Alkaline-Earth Oxides

1989 ◽  
Vol 152 ◽  
Author(s):  
Y. Chen ◽  
V. M. Orera ◽  
R. Gonzalezv ◽  
R. T. Williams ◽  
G. P. Williams ◽  
...  
Keyword(s):  
Hydrogen Concentration ◽  
Alkaline Earth ◽  
Oxygen Vacancies ◽  
High Pressures ◽  
Metallic Cation ◽  
Thermochemical Reduction ◽  
The One ◽  
Oxide Crystals ◽  
Positively Charged ◽  
F Centers

To a greater or lesser extent, all alkaline-earth oxide crystals contain hydrogen. Thermochemical reduction (TCR) of MgO and CaO crystals at high temperatures (˜2000K) and high pressures (4 to 7 atmospheres) of the metallic cation vapor (Mg and Ca respectively) results in a stoichiometric deficiency of oxygen ions, creating F centers (oxygen vacancies each with two electrons) and H− ions (protons in the anion sublattice, each occupied by two electrons). The positively-charged H− ions serve as traps for electrons excited from the F centers. Steady-state photo-excitation of the F absorption band results in F luminescence which typically extends to several minutes. This photoluminescence is detrimental for certain applications, such as tunable lasers. We have been able to reduce the hydrogen concentration prior to TCR of MgO and during TCR of CaO. The result is that the oxygen vacancies are predominantly in the one-electron F+ charge state. In contrast to the F luminescence, the decay of the F+ luminescence does not exhibit long phosphorescence. The prevalence of the F+ over the F state is found to be a function not only of the hydrogen concentration but also the severity of the thermochemical reduction.

Spectroscopic properties and cold elastic collisions of alkaline-earth Mg + Mg+ system

2018 ◽  
Vol 51 (19) ◽  
pp. 195201 ◽  
Author(s):  
Nissrin Alharzali ◽  
Dibyendu Sardar ◽  
Rim Mlika ◽  
Bimalendu Deb ◽  
Hamid Berriche
Keyword(s):  
Alkaline Earth ◽  
Spectroscopic Properties ◽  
Elastic Collisions

Conditions for atomic imaging of mullite

1989 ◽  
Vol 47 ◽  
pp. 418-419
Author(s):  
T. A. Epicier ◽  
G. Thomas
Keyword(s):  
Oxygen Vacancies ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Work Conditions ◽  
Real Space ◽  
Potential Candidate ◽  
Silicate Mineral ◽  
Resolution Electron ◽  
The Subject ◽  
Aluminium Silicate

Mullite is an aluminium-silicate mineral of current interest since it is a potential candidate for high temperature applications in the ceramic materials field.In the present work, conditions under which the structure of mullite can be optimally imaged by means of High Resolution Electron Microscopy (HREM) have been investigated. Special reference is made to the Atomic Resolution Microscope at Berkeley which allows real space information up to ≈ 0.17 nm to be directly transferred; numerous multislice calculations (conducted with the CEMPAS programs) as well as extensive experimental through-focus series taken from a commercial “3:2” mullite at 800 kV clearly show that a resolution of at least 0.19 nm is required if one wants to get a straightforward confirmation of atomic models of mullite, which is known to undergo non-stoichiometry associated with the presence of oxygen vacancies.Indeed the composition of mullite ranges from approximatively 3Al2O3-2SiO2 (referred here as 3:2-mullite) to 2Al2O3-1SiO2, and its structure is still the subject of refinements (see, for example, refs. 4, 5, 6).

THERMOLUMINESCENCE IN ALKALINE-EARTH DOPED KCl IRRADIATED AT ROOM TEMPERATURE

1976 ◽  
Vol 37 (C7) ◽  
pp. C7-158-C7-158
Author(s):  
A. RASCÓN ◽  
J. L. ALVAREZ RIVAS
Keyword(s):  
Alkaline Earth ◽  
Room Temperature
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