Ordering of cations in the voids of the anionic framework of the crystal structure of catapleiite

Crystal Chemistry of the Microporous Zirconosilicate Na6Zr3[Si9O27], a Product of High-Temperature Transformation of Catapleiite, and Its Ag-Exchanged Form

“…The IR spectrum of an analogous pellet of pure KBr was used as a reference. [8], (b) the product of its high-temperature transformation Na 6 Zr 3 [Si 9 O 27 ] drawn after [4], and (c) the Ag-exchanged form of Na 6 Zr 3 [Si 9 O 27 ] (only the "main" Ag sites are shown for better clarity).…”

“…Here we report data for the Ag-exchanged form of Na 6 Zr 3 [Si 9 O 27 ]. The crystal data of both initial Na 6 Zr 3 [Si 9 O 27 ] and its Ag-exchanged form are reported in Table 1.…”

“…The zirconosilicate Na 6 Zr 3 [Si 9 O 27 ] obtained by annealing of catapleiite at 1000 • C was used for ion-exchange experiments carried out in titanium alloy (VT-8) autoclaves that had about 10-mL capacity. A 0.05 g sample of Na 6 Zr 3 [Si 9 O 27 ] was placed in 5 mL of 1 M AgNO 3 aqueous solution and heated for 30 days at 250 • C. The solid products were carefully washed free from entrained salts by deionized water and dried at 60 • C before further investigations.…”

“…Aikuaiventchorr in the Khibiny alkaline complex (Kola peninsula, Russia) has been investigated by means of X-ray diffraction, electroconductivity measurements (using impedance spectroscopy), DSC, TG, and IR spectroscopy [4]. It was revealed that two-step exothermal transformation preceded by dehydration results in the formation of the compound with the simplified formula (Na 6-2x Ca x x )Zr 3 [Si 9 O 27 ] with x < 1 (the idealized formula can be written as Na 6 Zr 3 [Si 9 O 27 ]) which remains stable down to room temperature. This compound drastically differs in the structure from catapleiite: its structure is based on the heteropolyhedral framework which is built of nine-membered rings [Si 9 O 27 ] formed by SiO 4 tetrahedra which are connected with isolated [ZrO 6 ] octahedra.…”

“…Extra-framework Na (with admixed Ca) cations are located in wide channels of the framework and between the rings of SiO 4 tetrahedra [4]. The crystal structures of catapleiite and Na 6 Zr 3 [Si 9 O 27 ] are shown in Figure 1a,b. The topology of the heteropolyhedral framework of the latter and dimensions of zeolite-like channels allowed us to assume for it ion-exchange properties that were confirmed in [5].…”