Hydrothermal Synthesis, Crystal Structure, Solid-State NMR Spectroscopy, and Ionic Conductivity of Na₅InSi₄O₁₂, a Silicate Containing a Single 12-Membered Ring

Abstract

Na 5 InSi 4 O 12 has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. It is isotypic to Na 5 ScSi 4 O 12 . The structure consists of 12-membered single rings of corner-sharing SiO 4 tetrahedra linked together via corner sharing by single InO 6 octahedra to form a 3-D framework that delimits two types of channels along the c-axis. There are six independent sodium sites. The Na atoms within the 12-ring channels are immobile and the Na atoms within 7-ring channels are highly mobile. The 29 Si MAS NMR exhibits one Q 3 and one Q 4 resonance, each of which is split into two peaks because of inequivalent chemical environments caused by partially occupied Na sites in the 7-ring channels. Na ion conductivity measurements on a pressed pellet of the title compound were performed. The Arrhenius plot of dc conductivity shows a change in slope near 220 °C. We attribute this to the activation of the Na site that is situated between 7-ring channels and may serve as a connecting link between the channels. Crystal data: trigonal, space group R-3c (No. 167), a ) 21.7158(9) Å, c ) 12.4479(7) Å, and Z ) 18.

High-temperature, high-pressure hydrothermal synthesis, crystal structure and photoluminescent properties, of K3[Gd1−xTbxGe3O8(OH)2] (x = 0, 0.3, 0.1, 1)

“…7 Since then, a series of lanthanide silicates AV-n (n ¼ 9, 20, 22, 23) have been successfully prepared under mild hydrothermal conditions, their structures and ne-tuning luminescent properties derived from the multiple Ln 3+ ions have also been investigated. [8][9][10][11] High-temperature and highpressure hydrothermal synthetic method has also been used in exploratory syntheses of transition metals, 12,13 lanthanide elements, 14,15 and uranium-based [16][17][18][19] silicates because of the important roles of high pressure in the synthetic chemistry. 20 However, in contrast to the lanthanide silicates, much less work has been reported on the germanium analogues.…”

High-Temperature, High-Pressure Hydrothermal Synthesis, Crystal Structure, and Solid-State NMR Spectroscopy of Cs2(UO2)(Si2O6) and Variable-Temperature Powder X-ray Diffraction Study of the Hydrate Phase Cs2(UO2)(Si2O6)·0.5H2O

“…Recently a large number of hydrothermally synthesized silicates of transition metals and main group elements have been reported. − They show a rich structural chemistry, and some of them show good thermal stability, absorption, and ion-exchange properties. Most of these compounds were synthesized with alkali metal cations in a Teflon-lined autoclave under mild hydrothermal conditions at 180−240 °C.…”

Microporous Mixed Octahedral-Pentahedral-Tetrahedral Framework Silicates

“…For example, the structure of K 2 In(OH)Si 4 O 10 consists of unbranched vierer 4-fold chains of corner-sharing SiO 4 tetrahedra running along the b axis linked together via corner sharing by chains of trans-cornersharing InO 4 (OH) 2 octahedra to form a three-dimensional framework which delimits 8-ring and 6-ring channels to accommodate K + cations (Hung et al 2003). Another case in point is Na 5 InSi 4 O 12 (Hung et al 2004) isotypic with Na 5 ScSi 4 O 12 (Merinov et al 1980). The structure consists of 12-membered single rings of corner-sharing SiO 4 tetrahedra linked together via corner sharing by single InO 6 octahedra to form a three-dimensional framework delimiting two types of channels along the c-axis.…”