Kinetic study of silver iodide film growth on silver at low temperatures (30-73° C)

Bose, Saswata; Sircar, S. C.

doi:10.1007/bf02644494

Cited by 7 publications

(9 citation statements)

References 35 publications

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“…It was further predicted that this phenomenon would prevail for the tarnishing reaction of any system with an ion-conducting reaction product. Enhancement in the rate of tarnishing under short circuiting was also observed by Patnaik et al [24] and Bose and Sircar [19,20] in Ag-I 2 system. They identified the migration of cations as the ratelimiting step during short-circuit conditions, which received further support from their study on the Ag-Cd system, where a further increase in the rate of iodination by short circuiting was observed.…”

Section: Introductionsupporting

confidence: 58%

“…The surfaces of each test specimen were prepared in the same manner as reported previously. [19,20,24] A platinum wire was spot welded at the center of one edge of each rectangular specimen. Then, the specimens were washed thoroughly, cleaned with a solution of 1: 10 dil nitric acid, rinsed in distilled water, and dried in acetone.…”

Section: A Materials and Specimen Preparationmentioning

confidence: 99%

“…The reactions were found to follow the parabolic law in both the regions. However, the parabolic rate constants in the thin and thick film regions were reported [19] to be proportional to and , respectively. The effect of a divalent cation like Cd ++ on the iodination rate of silver was studied by Smyth and Cutler, [15] Bose and Sircar, [20] and Gensch and Hauffe.…”

Section: Introductionmentioning

confidence: 96%

“…The effect of a divalent cation like Cd ++ on the iodination rate of silver was studied by Smyth and Cutler, [15] Bose and Sircar, [20] and Gensch and Hauffe. [21] It is reported [19,21] that the rate decreased in the presence of Cd. This was explained with the concept of increased silver vacancy concentration [ ] due to incorporation of Cd ++ in the AgI V' Ag lattice, which in turn decreased the concentration of electron holes in the valence band of the growing AgI.…”

Section: Introductionmentioning

confidence: 96%

“…Though it was reported [15] that the rate constant (k P ) is proportional to , Shiojiri et al [17,18] had subsequently 1/2 P I2 shown that the reaction of iodine with vacuum-deposited silver is independent of iodine pressure over a temperature range of 423 to 573 K. The rate was found to be parabolic but, surprisingly, it was reported to be inversely proportional to the reaction temperature. In an attempt to clarify these conflicting views, Bose and Sircar [19,20] investigated AgI film growth kinetics on both Ag and Cd-doped Ag in the thin (Ͻ6000 Å ) as well as thick (6,000 to 30,000 Å ) film ranges. The reactions were found to follow the parabolic law in both the regions.…”

Section: Introductionmentioning

confidence: 99%

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Influence of short circuiting on the kinetics and mechanism of iodide film growth on Ag and Cd-doped Ag

Kuiry¹,

Roy

Bose

1997

Metall Mater Trans B

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Results of iodination studies on pure Ag and Ag with 6000 ppm of Cd under normal and shortcircuit conditions in the temperature and iodine pressure ranges of 333 to 373 K and 0.067 to 6.078 kPa, respectively, are reported. Under all experimental conditions, the iodide film growth kinetics conform to parabolic rate law. The iodide films have been characterized by scanning electron microscopy (SEM), electron probe microanalysis (EPM), X-ray diffraction (XRD), and Auger electron spectroscopy (AES) analyses. The effect of a higher valent dopant like Cd in Ag is observed to decrease the rate of normal iodination, which suggests that the film growth process is controlled by migration of electron holes across the iodide layers. The presence of a short-circuit path enhances the rate of iodination for pure Ag. However, the iodination rate of Cd-doped Ag under short-circuit mode is found to be further enhanced compared to that for pure Ag. This has been explained on the basis of the ion migration mechanism. The pressure dependence of rate constants is found to follow a relation like k P ␣ for pure Ag and Cd-doped Ag under normal conditions. The corresponding 1/2 P I2 relations under short-circuit mode are observed to be k P ␣ and k P ␣ for Ag and Cd-doped 1/3 1/4 P P I I 2 2Ag, respectively. Arrhenius plots have yielded activation energy values of 25.8 and 15.2 kJ⅐mol Ϫ1 under normal and short-circuit conditions, respectively. The kinetic results of parabolic film growth have been explained with the help of defect equilibria, considering the predominance of Frenkel defects in pure and doped AgI lattices. The mechanism of film growth processes has been confirmed to be Wagner's electrochemical potential gradient-induced migration of defect species across the iodide layer.

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Section: Introductionsupporting

confidence: 58%

Section: A Materials and Specimen Preparationmentioning

confidence: 99%