New ways for purifying lead iodide appropriate as spectrometric grade material

Abstract

In order to overcome some unsolved problems of lead iodide purification such as lack of stoichiometry, decomposition, and polytype admixture, several purification methods were compared. Lead iodide from different suppliers and synthesized from lead nitrate and potassium iodide was purified by zone refining, by zone refining followed by sublimation, by repeated sublimation and by repeated evaporation under different conditions. Purification methods were evaluated by studying parameters of the purified material like decomposition, stoichiometry, purity, and polytype composition, and also taking into account purification yield and rate. Stoichiometry was measured by wet procedures, purity by inductively coupled plasma (ICP) and polytypes by powder X-ray diffraction. Sublimation and evaporation give the best stoichiometry (PbI 1 90 ), especially when compared with zone refining (PbI 1 40 ). Purification by 100 zone refining passes gives similar impurity concentration to purification by three evaporations. Furthermore, evaporation exhibits maximum yield and rate (16%/day). Therefore, the work performed indicates that evaporation in Ar atmosphere is the quickest and most efficient purification method for producing spectrometric grade lead iodide, avoiding material decomposition and achieving high purity, maintaining the best stoichiometry.

Bismuth Tri-Iodide Polycrystalline Films for Digital X-Ray Radiography Applications

“…That tendency will lead to a lack of stoichiometry-even for high purity material-which will cause charge transport deterioration. These considerations show another similarity between bismuth tri-iodide and lead iodide, since they both present similar decomposition and stoichiometry problems [19], [32].…”

“…When film growth was performed under an argon initial pressure of 100-600 mmHg, decomposition was not observed. This recourse has been employed successfully for purifying lead iodide and growing films from it [19], [21]- [23], [32], precisely because of lead iodide decomposition under vacuum conditions. As material decomposition can damage stoichiometry, measurements are being carried out to elucidate the possible influence of film composition on its properties.…”

Perspectives of the Heavy Metal Halides Family for Direct and Digital X-Ray Imaging

“…Mercuric iodide Aldrich 99% was purified by ten repeated sublimations, following a reported technique [20], mercuric bromide, lead bromide and mercurid bromide-iodide were also purified by repeated sublimation, while lead iodide and bismuth tri-iodide were synthesized from their nitrates and subcarbonates, respectively, and then purified by zone refining, followed by one sublimation, for stoichiometry restoration. Details about these syntheses and purification steps have been reported elsewhere [21,22].…”

Properties of solution grown PbI2 layers embedded in PVA

“…Small crystallites (a few micrometers in size) randomly distributed are formed by this method [2]. One possible drawback of PVD is concerned with the risk of PbI 2 decomposition [4]. This may lead to additional defect introduction in the material.…”