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

Phase transformations that take place in nanocrystalline AgS silver sulfide have been systematically studied at temperatures from 298 to 893 K. The crystal structures of the polymorphic modifications -AgS, -AgS, and -AgS of nanocrystalline AgS have been found. It is established that the interstitial spacings between ions of silver in the superionic phases -AgS and -AgS 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 "-AgS--AgS" and "-AgS--AgS" 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 AgS 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 -AgS argentite at 300 K during the co-deposition of AgS/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 -AgS argentite is most favorable for the appearance of AgS/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 -AgS argentite and ZnS sphalerite from the [] direction, are found. The formation of AgS/ZnS heteronanostructures, in which the interface is formed by the (0) ≡ (110) plane of ZnS sphalerite and the ( 0.4123) ≡ (1 1 0.4123) plane of -AgS argentite, is the most energetically favorable.