Edge‐Defined, Film‐Fed Growth (EFG) Technique for the Preparation of α‐Al₂O₃:C Crystal with Highly Sensitive Thermoluminescence Response

Abstract

In this work, α‐Al2O3:C, a highly sensitive thermoluminescence dosimetry crystal, was grown by the EFG method in which a graphite heating unit and shield acted as the carbon source during the growth process. The optical, luminescent properties and dosimetric characteristics of the crystal were investigated. The as‐grown crystal shows a single glow peak at 536 K, which is associated with Cr3+ ions. After annealing in H2 at 1673 K for 80 h, the crystal shows a single glow peak at 460 K and a blue emission band at 415 nm. The thermoluminescent response of the annealed crystal shows linear–sublinear‐saturation characteristics in the dose range from 5 × 10−6 to 100 Gy.

Impurities bound to vacancies in insulators: Electronic relaxation and physical properties of theCr3+−VMmodel center in KGarcía‐Fernández1, Trueba2, Garcia-Cueto3 et al. 2011Phys. Rev. B176681View full textAdd to dashboardCite

“…This fact is used to build sensitive x-ray dosimeters. 4 When an H c + cation of an insulating host lattice is replaced by an impurity ion I q + (q > c), this process also gives rise to the formation of complex centers where the impurity, I, is bound to one positive vacancy, V, or more. If the impurity is a transition-metal cation not coupled to any other defect, then its unpaired electrons are usually localized in the I X N unit formed with the nearest anions or ligands, X.…”

Influence of Pulling Rates on the Thermoluminescence and Optically Stimulated Luminescence of α‐Al2O3:C Crystals Grown by the Edge‐Defined, Film‐Fed Growth Technique

“…When the pulling rate increases, almost all the carbon reaching the surface diffuses into the crystals, and no residue carbon stayed on the surface after the growth. In our former experiment, 14 only a small amount of black material was found near the seed when the crystal was grown at the pulling rate of 0.3 mm/min. The different results can be attributed to the use of a graphite shield with different density.…”

“…The graphite heating unit and shield (Shanghai Toyo Tanso Co. Ltd., Shanghai, P. R. China), which act as the carbon source, were designed and used in the crystal growth furnace. Compared with the graphite shield used in our previous work, 14 a graphite shield with lower density was used this time in order to increase the quantity of carbon from the source during the crystal growth. A molybdenum die and crucible (Aluminum Corporation of China, Beijing, China) with a proper size were designed to grow α‐Al 2 O 3 :C crystals with the shape of a sheet.…”

“…4) under steady state conditions. In order to obtain dosimetry-grade a-Al 2 O 3 :C crystal, the as-grown crystals were annealed in H 2 at 1673 K for 80 h. 14 Figure 1 shows the photographs of the a-Al 2 O 3 :C crystal sheet grown by the EFG method with different pulling rates. Samples with dimensions of 5 mm  5 mm 1 mm were cut from the above crystal samples and polished.…”

“…However, the growth process of TGT is slow and the cost is too high for industrialization. Recently, α‐Al 2 O 3 :C crystal was successfully grown by the EFG method in our group 14 . In this method, the graphite heating unit and shield are used as the carbon source, and shaped α‐Al 2 O 3 :C crystal can be grown with a high pulling rate and low cost.…”