Influence of Cationic Dopants on the Thermal Annealing of Reactor-Irradiated K₂SeO₄

Abstract

Hot atom chemistry /Potassium selewte Z^5 Se /Impurity effects AbstractThe influence of the dopant cations Al 3+ , In 3+ and Ca 2+ on both thermal and gamma-annealing in neutron-irradiated K 2 Se0 4 has been studied. Assuming that the introduction of the dopant cations, M n+ , in the lattice leads to the creation of both M^* sites and K + -vacancies, Q k+ , the effect of the impurity on the initial retention is explained in terms of the overall efficiencies of these species for hole-capture, at a given temperature. Hole release from 33 K + on heating after irradiation should account for the changes brought about by the dopants in the experimental isochronal annealing curves. Simple kinetic models are proposed and calculated curves are shown as an illustration.

Chemical stabilization of recoil 56Mn in MnSO4-KClO4 mixed crystals following (n, γ) process

“…3 and 4). Similar curves were also obtained in other systems [6][7][8] but the saturation times were found to be different, possibly due to the varying degree of solid state reactions, affected by the nature of crystal defects (inherent or radiation induced) [11]. Increase in retention with increase in the time of heating at a particular temperature is obtained for both systems.…”

“…Cationic dopants tend to decrease the initial retention while anionic dopants tend to increase it [4,7]. Cationic dopants, like Ca 2+ doped in K 2 SO 4 , showed reduced initial retention but enhanced thermal annealing compared to their pure crystals after thermal neutron activation [6]. However, in case of anionic dopants there are anionic impurities present in KMnO 4 -KClO 4 , K 2 CrO 4 -K 2 BeF 4 and KBrO 3 -KClO 3 mixed crystals where both thermal annealing and initial retention increased compared to that of single crystals [7,8].…”

“…It has been inferred that doping by foreign materials or atoms of different valence states possibly changes the distribution of different recoil species as the transient reaction of metastable precursors are modified by the presence of defects in the irradiated matrix. The doped components allow introduction of controlled concentrations of different types of defects which participate in annealing reactions [5,6]. The solid state investigations reveal that the new species are formed only if a homogeneous mixture (mixed crystal) or double salts are used as targets.…”