Protons and Deuterons in Magnesium‐Doped Sapphire Crystals

Abstract

The OH‐ and OD‐ stretching frequencies in magnesium‐doped aluminum oxide crystals were determined by infrared absorption measurements. Two very broad bands centered at }3005 and 2228 cm‐1 were observed for OH‐ and OD‐, respectively. Polarization experiment results were compatible with OH‐ (OD‐) ions lying in the basal plane, as is the case in undoped crystals. The threshold temperature for the in‐diffusion of deuterons was obtained by annealing the samples in flowing D2O vapor; the resulting value was }1050 K. At 1223 K, the diffusion coefficient was }3× 10‐7 cm2/s, and the activation energy was 1.6 eV.

Theoretical infrared spectra of OH defects in corundum (<i>α</i>-Al<sub>2</sub>O<sub>3</sub>)

“…Although the band observed at 3010 cm −1 in the Mgdoped samples (Volynets et al, 1972;Ramírez et al, 1997b) is significantly broader than those observed in Ti-or V-doped samples, the models of interstitial protons associated with substituted Mg 2+ ions are consistent with experimental observation in terms of polarization properties and frequencies ( Table 2). The theoretical I z /I x ratio of the models (Table 2) ranges between 2.88 and 4.99, which compares favorably with the 3.33 ratio reported by Volynets et al (1972) and with the 5 : 1 ratio reported for the similar bands observed in Nior Co-doped samples (Eigenmann and Günthard, 1971).…”

“…The relative intensity of the OH-stretching bands in Ti-and V-doped samples experimentally treated at high temperature (1400 K) depends on their cooling rate (Ramírez et al, 2004), which is consistent with the record of a temperature-dependent distribution of OH defects displaying different clustering schemes. In addition, a broader band extending from 2900 to 3100 cm −1 with a dominant polarization in the direction perpendicular to the (001) plane is observed in Mg-doped samples (Volynets et al, 1972;Ramírez et al, 1997b). Broad bands with similar properties have been reported at 3025 and 2972 cm −1 in Coand Ni-doped samples, respectively (Eigenmann and Günthard, 1971).…”

Vacancy Defects in Ga2O3: First-Principles Calculations of Electronic Structure

“…Thus, it is likely that hydrogen impurity could be a “hidden” source, which drastically transforms the non-conductive β-Ga 2 O 3 to an n-type conductor. Note that hydrogen in oxides can present itself in different forms and have different charge states [ 50 , 51 , 52 , 53 , 54 ], which, in principle, complicates the overall picture for understanding.…”

Slip and Twinning in Polycrystalline Alumina (α‐Al2O3) Deformed under Hydrostatic Pressure between 600° and 1000°C

“…29,30 Their presence tends to decrease the surface energy of the basal plane. 29,31 It has also been noted that anisotropic grain growth is observed at high temperature near alumina surfaces in Ar/H 2 O environment. 32 This anisotropy is associated with the development of basal GB planes.…”