Polymorphic Phase Transformations in Nanocrystalline Ag2S Silver Sulfide in a Wide Temperature Interval and Influence of Nanostructured Ag2S on the Interface Formation in Ag2S/ZnS Heteronanostructure

Abstract

Phase transformations that take place in nanocrystalline Ag2S silver sulfide have been systematically studied at temperatures from 298 to 893 K. The crystal structures of the polymorphic modifications α-Ag2S, β-Ag2S, and γ-Ag2S of nanocrystalline Ag2S have been found. It is established that the interstitial spacings between ions of silver in the superionic phases β-Ag2S and γ-Ag2S are noticeably smaller than diameter of the Ag+ ion. As a result of which, the probabilities of filling the sites of the metal sublattices of these phases with Ag atoms are very small. It was found that the “α-Ag2S—β-Ag2S” and “β-Ag2S—γ-Ag2S” transitions between polymorphic modifications of silver sulfide occur as phase transformations of the first order at temperatures of ~440–442 K and ~850–860 K. The structure of interface forming by nanostructured Ag2S and ZnS is considered, taking into account the anisotropy of elastic properties of these sulfides. It is established that a large amount of cubic zinc sulfide stabilizes the cubic structure of β-Ag2S argentite at 300 K during the co-deposition of Ag2S/ZnS heteronanostructures from colloid solutions. It is found that placing Ag atoms at four crystallographic positions located in one plane of the unit cell of cubic β-Ag2S argentite is most favorable for the appearance of Ag2S/ZnS heterostructures. The smallest strain distortions at the interface are observed at the minimum difference of shear moduli of the components forming heteronanostructure. The distributions of elastic characteristics, including the shear moduli of monocrystalline particles of cubic β-Ag2S argentite and ZnS sphalerite from the [hkl] direction, are found. The formation of Ag2S/ZnS heteronanostructures, in which the interface is formed by the (hk0) ≡ (110) plane of ZnS sphalerite and the (hk 0.4123) ≡ (1 1 0.4123) plane of β-Ag2S argentite, is the most energetically favorable.

Synthesis and Photocatalytic Applications of Silver Sulfide Nanostructures: Recent Advancement

“…Authors observed that by increasing the temperature to around 450 K, nanoparticles grow insignificantly, which indicates the thermal stability of silver sulfide up to this temperature [60]. The authors of the work reported the phase transformation of silver sulfide synthesized via hydrochemical deposition method over a wide range of temperatures [7]. Raid A Ismail et al investigated the effect of deposition time on the synthesis of Ag 2 S nanofilm.…”

“…Among various metal sulfides, silver sulfide (Ag 2 S) is a distinctive binary metal chalcogenide semiconductor material with a narrow and direct band gap of around 1ev and high absorption coefficient of approximately 10 6 cm [4][5][6]. Studies suggest that silver sulfide has a layered structure that exists in three polymeric forms [7]. Phase diagrams [8] predict that below 450 K α-Ag 2 S, the semiconducting phase exists.…”

硫化物の溶融温度に関する現象論的理解

“…増え不規則構造化すること [23][24][25] ，後二者の高温相は S 2 − 格 子内に多数箇所存在するカチオンサイトにカチオンが分 散分布するため液体状態に近いこと [26][27][28][29] が知られており，…”