VUV and cathodoluminescence spectroscopy of 12CaO · 7Al2O3

Abstract

Reflection, photo-and cathodoluminescence of 12CaO Á 7Al 2 O 3 (C12A7) were investigated. Smooth features observed in VUV reflection spectrum of monocrystalline C12A7 evidence its complicated crystalline structure and lattice disorder. Two luminescence bands peaking at 4.9 and 3.35 eV were revealed in C12A7 ceramics having encaged electrons and O 2-ions. The 4.9 eV emission has an excitation onset at 6.8 eV, i.e. near the threshold of free electron-hole pair creation, and is assigned to the recombination of encaged electrons with valence band holes. The 3.35 eV emission is ascribed to the recombination of electrons with the holes localized at the encaged O 2-ions.

Mixed Electrical Conduction of Calcium Aluminates Synthesized by Polymeric Precursors

“…The BG shown here is lower than that reported by Feldbach et al 36 from their luminescence measurements. They found a band gap of 6.3 eV for C12A7, while other authors found one of 5.89 eV, 15,36 which is also a reasonable value for the mayenite compound, whose theoretical BG is situated at up to 6.80 eV. In the same way, another work reported a value of 6.30 eV for C12A7.…”

“…Medvedeva et al 33 and Miyakawa et al 34 reported a low value of 4.50 eV for the band gap using first principle calculations, whereas the electrical properties of mayenite have been widely explored. 15,33,35,36 No paper reporting the electrical transport properties of self-modified compounds of celite plus mayenite was found.…”

12.4: Surface Exciton Properties of MgO in ZnO‐MgO Core‐Shell Quantum‐Dots

“…Such a shell passivation could reduce the surface-related defect states as well as confine the charge carriers into the core region due to the band offset potentials, resulting in more efficient and photostable luminescent nanocrystals [4, 13 -15 ]. The large value of the exciton binding energy of MgO (80 meV) [16] and small radius (1.5 nm) [17] is advantageous for exciton transport. The bottom of the conduction-band of MgO crystals is located around the vacuum energy (depending on the reference, the electron affinity is stated as either positive or negative [18][19][20][21]).…”

Novel Binary Calcia–Alumina Systems for Device Applications

“…C12A7 conceptually follows a different route for its induced conductivity. This conductive oxide belongs to a new class of novel materials known as "electrides" [7][8][9].…”