Novel open-framework europium silicates prepared under high-temperature and high-pressure conditions

摘要

Two new europium silicates, Na_(15)Eu_3Si_(12)O_(36) (denoted as 1) and K_2EuSi_4O_(10)F (denoted as 2), were successfully synthesized under high-temperature and high-pressure conditions, and structurally characterized by single-crystal and powder X-ray diffraction (XRD). The single-crystal XRD analysis of 1 reveals that its structure is based on [Si_6O_(18)]n~(12n?) cyclosilicate anions that are built from six SiO_4 tetrahedra sharing two of their four O corners with each other. Such [Si_6O_(18)]n~(12n?) cyclosilicate anions are linked via EuO_6 octahedra to form a three-dimensional (3D) framework containing 6-membered ring channels delimited by the SiO_4 tetrahedra and EuO_6 octahedra along the [010] direction. The structure of 2 consists of infinite tubular chains of corner-sharing SiO_4 tetrahedra, which are further linked together via corner sharing O atoms by infinite chains of EuO_4F_2 octahedra forming a 3-D framework that contains 8-ring and 6-ring channels along the [010] direction. The photoluminescence properties of 1 and 2 were also investigated.