Crystal structure and dynamical properties of a new tellurite: AgTlTeO3

The structure of a newly synthesized AgTlTeO3 crystalline compound has been solved from single crystal X-ray diffraction data and refined to a final reliability factor R1 = 0.037. It was found having an orthorhombic Iba2 space group symmetry with unit cell parameters a = 14.708(7) Å, b = 10.745(6) Å, c = 5.166(3) Å, Z = 8. Its lattice is divided into separated AgTlTeO3 sheets parallel to [0 1 0] which are formed by TeO3 pyramids, TlO4 disphenoids and AgO6 octahedra sharing either corners or edges. At the same time, from the crystal chemistry point of view, it can be classified as a typical island-type compound made up from molecular-like [TeO3]2− ortho-anions weakly connected with Ag+ and Tl+ cations. The vibrational spectra and their interpretations complemented by the calculated elastic properties confirm this classification. The model-estimated piezoelectric constants allow characterizing AgTlTeO3 as a strong pyroelectric structure.