Synthesis, Structure, and Electric Conductivity of Ferrous Tainiolite and Its Oxidative Conversion into Coarse-Grained Swellable Smectite

Abstract

Ferrous tainiolite, Cs[Fe2Li] o [Si4] t O10F2, has been synthesized from the melt in gastight molybdenum crucibles. The electric conductivity has been measured by impedance spectroscopy. As compared to natural micas, which are insulators, good conductivity is observed. The layered silicate can be further modified by ion exchange, which makes it a promising host structure for sensor materials. The estimated activation energy is as low as 0.79 eV. Upon Ba2+ exchange for Cs+, structural Fe2+ is partially oxidized (33%), and the layer charge is reduced significantly, resulting in a coarse-grained but swollen (monolayer hydrate) smectite-type layered silicate. Therefore, further functionalization by pillaring will be feasible resulting in a conducting microporous material. The new material has been characterized by the analysis of chemical composition (wavelength dispersive X-ray spectroscopy and laser ablation-inductively coupled plasma−mass spectrometry), differential thermal analysis, electron microscopy, Mössbauer, UV−vis/NIR, impedance spectroscopy, and single-crystal structure refinement (wR(F 2) = 0.0883). The structure is of the 1M polytype (C2/m) with cell parameters a = 5.277(2) Å, b = 9.148(2) Å, c = 10.804(2) Å, and β = 99.19(3)°. The congruent melting point was observed at 1103 (±5) K.

Zugang zu mikroporösen Materialien durch oxidatives Pillaring von Glimmern

“…[12] [18] unter Verwendung einer Kristallbeschreibung, die mit dem Programm X-SHAPE [18] (2) 3 , Z = 2, 1 ber. = 2.157 g cm À3 .…”

“…Bindungslängen und -winkel der Silicatschichte in der Intercalationsverbindung stimmen gut mit denen in der Ausgangssubstanz Cs-Täniolit überein. [12] Es sind viele andere Schichtsilicate bekannt, die wesentlich flexiblere Schichten aufweisen [15] oder die leicht delaminiert [12] untersucht werden. Von Interesse sind eine mögliche Anwendung als redoxaktives Sensormaterial (z.…”

Gas Sensitivity of Pillared and Non‐pillared Layered Silicates

“…Single crystals of synthetic fluoro tainiolite Cs 1 [Fe 2 Li 1 ]<Si 4 >O 10 F 2 1 were compared with crystals that have been pillared by cation exchange applying N,N‐dimethyl‐1,4‐diazabicyclo[2.2.2]octane [2, 3] (Me 2 DABCO 2+ ) 0.22 [Fe 1.85 2+/3+ Li 0.9 , 0.25 ]<Si 4 >O 10 F 2 . Crystals of both compounds were mounted on planar gold electrodes to measure the influences of different gases (CO, NO, NH 3 , H 2 , C 3 H 8 ) on the conductivity σ.…”

A Route to Microporous Materials through Oxidative Pillaring of Micas

“…Unlike natural micas, which show no intracrystalline reactivity owing to the high layer charge, this synthetic mica readily undergoes cation exchange by an oxidative intercalation mechanism. Concomitantly with cation exchange, the layer charge is reduced all the way to the range of smectites by oxidation of structural Fe 2+ ions (see reference [12] for details).…”

“…In contrast to PILCs made of naturally occurring and hydrothermally synthesized layered silicates, this compound is three-dimensionally ordered and reveals in-depth structural details. Owing to the high structural Fe content, the PILC described here provides a size-selective, shape-selective, and at the same time electronically conducting [12] framework. Its applicability as a sensor for redox-active ambient gas species (e.g.…”