Synthesis, Structure Determination, and Aqueous Durability of Cs₂ZrSi₃O₉

Abstract

The structure of Cs 2 ZrSi 3 O 9 synthesized using a sol-gel method was determined from the Rietveld refinement of experimental powder X-ray diffraction data. The refinement confirmed that this compound was isostructural with wadeite: its structure was hexagonal (space group P6 3 /m), and its lattice parameters were a ‫؍‬ 7.2303(2) Å and c ‫؍‬ 10.2682(4) Å. The aqueous durability of Cs 2 ZrSi 3 O 9 varied, depending on the solution conditions. In modified leach tests with buffered (pH 7) and unbuffered solutions, the 7-d cesium release rates were <1.2 ؋ 10 ؊4 g⅐(m 2 ⅐day) ؊1 , which indicated high aqueous durability. However, in unsaturated, unbuffered solutions with a pH of 9 -10, the durability was much lower, with 7-d cesium release rates of 2.2 ؋ 10 ؊3 g⅐(m 2 ⅐day) ؊1 . The ability of this material to retain cesium in aqueous environments can be explained by its condensed ring structure, in which the size of the channel openings is smaller than the diameter of a Cs ؉ ion. However, dissolution of the network silicate occurred at high pH, which resulted in the release of cesium.

Thermochemistry and Aqueous Durability of Ternary Glass Forming Ba‐Titanosilicates: Fresnoite (Ba2TiSi2O8) and Ba‐Titanite (BaTiSiO5)

“…Calculated FR% and normalized Ba leaching rate ( NL ) data of the PCT conducted on fresnoite glass A and crystal E are shown in Table IV. The normalized Ba leaching rate ( NL ) observed for both glass and crystal samples decreased as a function of time, comparable to other titanosilicates 46,47 . The changes in NL values for glass A show more severe drops than crystal E. For example, the 10‐d NL value of A was 23% of the 3‐d NL value, while the 10‐d NL value of E was 39% of the 3‐d NL value.…”

“…For example, 3‐d NL (A)/3‐d NL (E) is equal to 1.20, and 10‐d NL (A)/10‐d NL (E) is 0.74. We note that the saturation effect, which may affect NL values by a factor of five, especially for a long‐term test, is not considered in this test 46 . For crystal E, the 10‐d NL value was 3.20 × 10 −3 (g·(m 2 d) −1 ), suggesting an appreciable higher stability compared with other ceramics, such as borosilicates (10 −2 (g·(m 2 d) −1 )) 48,49 …”

New Fission-Product Waste Forms: Development and Characterization

“…Calculated fraction released (FR%) and normalized Ba leaching rate (NL) data of the product consistency test (PCT) conducted on fresnoite glass (A) and crystal (E), are shown in Table I. The normalized Ba leaching rate (NL) observed for both glass and crystal samples decreased as a function of time, comparable to other titanosilicates 2,3 . The changes in NL values for glass (A) showed more severe drops than crystal (E).…”

Novel blue and green phosphors obtained from K2ZrSi3O9:Eu2+ compounds with different charge compensation ions for LEDs under near-UV excitation

“…There is only one lattice site for K, Zr and Si. [27][28][29] The chemical composition of this compound is further determined by EDX, as shown in Fig. 1b.…”

“…There is only one lattice site for K, Zr and Si. 27,28 In this study, the structure and photoluminescence properties of wadeite K 2 ZrSi 3 O 9 doped with Eu 2+ phosphors were studied for the first time. By co-doping different ions and adjusting the occupation sites of Eu 2+ , blue and green light can be yield from K 2 ZrSi 3 O 9 :Eu 2+ .…”