New lanthanide silicates based on anionic silicate chain, layer, and framework prepared under high-temperature and high-pressure conditions

摘要

Three new lanthanide silicates K_(1.25)Gd_(1.25)Si _(2.5)O_(7.5) (denoted as GdSiO-CJ7), Cs_3TbSi _8O_(19)?2H_2O (denoted as TbSiO-CJ8), and Cs_3DySi_6O_(15) (denoted as DySiO-CJ9) were synthesized by using a high-temperature and high-pressure hydrothermal method. Their structures determined by single-crystal X-ray diffraction revealed anionic silicate chain, layer and framework, which are further connected with LnO _n polyhedra to form novel lanthanide silicate frameworks. The structure of GdSiO-CJ7 consists of unbranched silicate chains [Si _5O_(15)]~(10-) extending along the b axis, which are linked together by edge-sharing linked GdO_6 and GdO_8 chains along the c axis to form a 3-D framework with two types of 10-ring channels along the [010] and [001] directions, respectively. The structure of TbSiO-CJ8 consists of double 4,8-net sheets [Si_8O_(19)] ~(6-) built up from SiO_4 tetrahedra, which are linked together via TbO_6 octahedra to form a 3-D framework with 8-ring channels along the [100] and [010] directions. The structure of DySiO-CJ9 is based on a 3-D silicate framework [Si_6O_(15)]~(6-) with 6-rings, where DyO_6 octahedra are located between two adjacent 6-rings and connected with six Si atoms via O atoms. The photoluminescence photoluminescence properties of TbSiO-CJ8 and EuSiO-CJ8 were investigated.