Crystal Chemistry of Chalcogenide Perovskites and Related Materials

English Abstract:

There have been numerous studies of oxide perovskites with ABO₃ stoichiometry that show how the flexible structure of perovskite can accommodate a variety of A and B-site atoms, yielding a variety of properties that are exploited in technological applications. Recently, there has been growing interest in ABX₃ (X=S,Se) perovskites including their potential use in photovoltaic applications [1]. Many ABX₃ chalcogenides have been reported that adopt the well-known GdFeO₃ perovskite structure with Pnma symmetry. Examples of sulfide perovskites include CaZrS₃, SrZrS₃, BaZrS₃, BaUS₃, CaHfS₃, BaHfS₃, EuZrS₃, and EuHfS₃ [2]. Moreover, substitution of sulfur (and selenium) for oxygen in ABX₃ leads to a number of structure types not commonly observed in ABO₃ compounds, including the NH₄CdCl₃ structure which has been observed in SnZrS₃, PbZrS₃, SnHfS₃, PbHfS₃, Sn₂S₃, EuZrS₃, LaCrSe₃ [3 and references therein] and more recently reported in SrZrS₃ [4] and SrZrSe₃ [5]. In some cases such as BaTiS₃, a hexagonal phase belonging to space group P63/mmc with the BaNiO₃ structure has been reported [6]. In this presentation, we explore how substitution of A- and B-site atoms in ABS₃ compounds affects the stability of the perovskite and related structures. In addition, we will present bond valence that provide insight into the factors that affect the stabilities of these structures. Thirdly, we will apply the model that our group developed to predict the high-pressure behavior of ABO₃ perovskites [7] to chalcogenide perovskites. This model predicts the site compressibilities from site parameters defined in terms of their coordination number, average bond length at room pressure and bond valence parameters. We will use this model to predict possible high-pressure phase transitions in chalcogenide perovskites.

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