Ternary sulfides ALnS2:Eu2+ (A = Alkaline Metal, Ln = rare-earth element) for lighting: Correlation between the host structure and Eu2+ emission maxima

Ternary sulfides ALnS2 (A = Alkaline Metal, Ln = rare-earth element) doped with the Eu2+ ions are characterized by a very wide range of tunability of the Eu2+ emission maxima with the host's chemical composition. In the present work, a detailed analysis of the structural properties of these materials was performed. It was shown that their lattice constants can easily be expressed as the linear functions of the ionic radii and electronegativities of the constituting elements. As a further step, the relations between the structural properties of the hosts and optical properties of the Eu2+ dopant were analyzed. It was demonstrated that the position of the Eu2+ emission maxima is a linear function of the so-called hexagonality ratio c/a, where c and a are the lattice constants of the rhombohedral ternary sulfides. The obtained results can be used as helpful guides for manufacturing Eu2+-doped ternary sulfides with desired emission properties with high potential for white LEDs applications.