skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: How hydrothermal synthesis improves the preparation of (Zr,Ce)SiO 4 solid solutions
Although ZrSiO 4 is the most well-known compound in the zircon-structured family (space group I41/amd), the experimental conditions for preparing pure and well-crystallized phases which are doped with tetravalent element via hydrothermal synthesis has never been clearly discussed in the literature. With the aim to answer this question, the experimental conditions of preparation of ZrSiO 4 and (Zr,Ce)SiO 4 were investigated in order to synthesize well-crystallized and pure phases. A multiparametric study has been carried out using soft hydrothermal conditions, with variables including reactant concentration, initial pH of the reactive medium, and duration of the hydrothermal treatment. Pure ZrSiO 4 was obtained through hydrothermal treatment for 7 days at 250°C, within a large acidity range (1.0 ≤ pH ≤ 9.0) and starting from C Si ≈ C Zr ≥ 0.2 mol·L -1 . As hydrothermally prepared zircon structured phases can be both hydrated and hydroxylated, its annealed form was also studied after heating to 1000°C. Based on these results, the synthesis of (Zr,Ce)SiO 4 solid solutions were also investigated. The optimal hydrothermal conditions to acquire pure and crystallized phases were obtained in 7 days at 250°C with initial pH = 1 and concentration of the reactants equal to 0.2 mol·L -1 . This led to (Zr,Ce)SiO 4 solid solutions with the incorporated Ce content up to 40 mol.%. Samples were characterized by multiple methods, including lab and synchrotron PXRD, IR and Raman spectroscopies, SEM, and TGA. Moreover, it was found that these phases were thermally stable in air up to at least 1000°C.  more » « less
Award ID(s):
2144792
PAR ID:
10428219
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Dalton Transactions
ISSN:
1477-9226
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, Geochemistry, Geophysics, Geosystems)
    Abstract Stable and inert under most conditions, zircon can be dissolved and precipitated by aqueous fluids in the upper crust. Geochemical models using currently available thermodynamic properties for Zr aqueous species at 0.2 GPa predict that zircon solubility increases with temperature from 400 to 900°C in fluids saturated with quartz or baddeleyite. Zircon solubility is low in near‐neutral pH fluids and enhanced in acidic and alkaline fluids. Adding NaOH and to a lesser extent NaF to the solution significantly increases the solution pH values and Zr concentrations at zircon saturation. Modeled Zr concentrations are often orders of magnitude different from zircon solubilities measured experimentally under similar conditions. Metamict (amorphous) ZrSiO4is more soluble than crystalline zircon and is replaced through a coupled dissolution‐precipitation process. Reaction path kinetics models were constructed to simulate experiments described in the literature and extract rate constants for replacement of metamict ZrSiO4. Replacement is rate limited by zircon precipitation and is nearly complete after 1 week when fluid is present at 600°C, with the rate of replacement increasing with temperature. In a closed system, hydrothermal zircon may form by replacement of radiation‐damaged zircon but not fully crystalline zircon. Replacement of metamict ZrSiO4forms characteristic porosity. Geochemical models identify the conditions that promote zircon solubility, metamict ZrSiO4replacement, and the formation of hydrothermal zircon, and provide constraints on the interpretation of zircon U‐Pb dates of hydrothermal events. 
    more » « less
  2. ; (, Journal of the American Ceramic Society)
    Abstract In this report, a facile wet chemical method using acetonitrile combined with thermal annealing was used to prepare Li2S‐P2S5(LPS) based glass‐ceramic electrolytes with (1 wt%, 3 wt%, and 5 wt% Ce2S3) and without Ce2S3doping. The crystal structure, ionic conductivity, and chemical stability of Li7P3S11glass‐ceramic electrolytes were examined at varying temperatures (250–350°C). The results indicated that the highest ionic conductivity of 3.15 × 10−4S cm−1for pure Li7P3S11was observed at a temperature of 325°C. By incorporating 1 wt% Ce2S3and subjecting it to a heat treatment at 250°C, the glass ceramic electrolyte attained a remarkable ionic conductivity of 7.7 × 10−4(S cm−1) at 25°C. Furthermore, it exhibited a stable and extensive electrochemical potential range, reaching up to 5 volts when compared to the Li/Li+reference electrode. By tuning the glass transition and crystallization temperature, cerium doping seems to make Li7P3S11more chemically stable, compared to its original 70Li2S‐30P2S5counterpart. According to Raman and X‐ray photoelectron spectroscopy analyses, cerium doping inhibits the decomposition of highly conductive P2S74‐(pyro‐thiophosphate) to PS43−and P2S64−. Doped LPS has a greater crystallinity and more uniform microstructure than pure LPS, according to XRD, Raman spectroscopy, and scanning electron microscopy analysis. Consequently, Li7P2.9Ce0.1S11electrolyte shows great potential as a solid‐state electrolyte for constructing high‐performance sulfide‐based all‐solid‐state batteries. 
    more » « less
  3. ; ; ; ; (, Dalton Transactions)
    The reactivity of alkali–manganese( ii ) and alkali trifluoroacetates towards amorphous SiO 2 (a-SiO 2 ) was studied in the solid-state. K 4 Mn 2 (tfa) 8 , Cs 3 Mn 2 (tfa) 7 (tfaH), KH(tfa) 2 , and CsH(tfa) 2 (tfa = CF 3 COO – ) were thermally decomposed under vacuum in fused quartz tubes. Three new bimetallic fluorotrifluoroacetates of formulas K 4 Mn 3 (tfa) 9 F, Cs 4 Mn 3 (tfa) 9 F, and K 2 Mn(tfa) 3 F were discovered upon thermolysis at 175 °C. K 4 Mn 3 (tfa) 9 F and Cs 4 Mn 3 (tfa) 9 F feature a triangular-bridged metal cluster of formula [Mn 3 (μ 3 -F)(μ 2 -tfa) 6 (tfa) 3 ] 4− . In the case of K 2 Mn(tfa) 3 F, fluoride serves as an inverse coordination center for the tetrahedral metal cluster K 2 Mn 2 (μ 4 -F). Fluorotrifluoroacetates may be regarded as intermediates in the transformation of bimetallic trifluoroacetates to fluoroperovskites KMnF 3 , CsMnF 3 , and Cs 2 MnF 4 , which crystallized between 250 and 600 °C. Decomposition of these trifluoroacetates also yielded alkali hexafluorosilicates K 2 SiF 6 and Cs 2 SiF 6 as a result of the fluorination of fused quartz. The ability to fluorinate fused quartz was observed for monometallic alkali trifluoroacetates as well. Hexafluorosilicates and heptafluorosilicates K 3 SiF 7 and Cs 3 SiF 7 were obtained upon thermolysis of KH(tfa) 2 and CsH(tfa) 2 between 200 and 400 °C. This ability was exploited to synthesize fluorosilicates under air by simply reacting alkali trifluoroacetates with a-SiO 2 powder. 
    more » « less
  4. ; ; ; (, Journal of Analytical Atomic Spectrometry)
    Zirconium (Zr) plays a key role in the development of phases like zircon (ZrSiO 4 ) and baddeleyite (ZrO 2 ) in magmatic systems. These minerals are crucial for the study of geologic time and crustal evolution, and their high resistivity to weathering and erosion results in their preservation on timescales of billions of years. Although zircon and baddeleyite may also preserve a robust record of Zr isotope behavior in high-temperature terrestrial environments, little is known about the factors that control Zr isotope partitioning in magmatic systems, the petrogenetic significance of fractionated compositions, or how these variations are recorded in Zr-rich accessory phases. Here, we describe a new analytical protocol for accurately determining the Zr stable isotope composition of zircon by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), using the double-spike method to correct for procedural and instrumental mass bias. We apply this technique to test whether zircon crystallization in carbonatite magmatic systems is a driver of Zr isotope fractionation by interrogating the internal zonation of a zircon megacryst from the Mud Tank carbonatite (MTUR1). We find the MTUR1 megacryst to lack internal zoning within analytical uncertainties with a mean μ 94/90 Zr NIST = −55 ± 28 ppm (2 SD, n = 151), which suggests that zircon crystallization is not a driver of Zr isotope fractionation in carbonatite magmas. This observation is in stark contrast with those made in silicate magmatic systems, raising the possibility that the bonding environment of Zr 4+ ions may be fundamentally different in carbonatite vs. silicate melts. Because of its remarkable homogeneity, the MTUR1 megacryst is an ideal natural reference material for Zr isotopic analysis of zircon using both solution and spatially resolved methods. The reproducibility of a pure Zr solution and our chemically purified zircon fractions indicate that the external reproducibility of our method is on the order of ±28 ppm for μ 94/90 Zr, or ±7 ppm per amu, at 95% confidence. 
    more » « less
  5. ; ; ; ; ; (, Minerals)
    Zircon xenocrysts from alkali basalts in Ratanakiri Province, Cambodia represent a unique low-Hf zircon within a 12,000 km long Indo-Pacific megacryst zone. Colorless, yellow, brown, and red crystals ({100}, {101}, subordinate {211}, {1103}), with hopper growth and corrosion features range up to 20 cm in size. Zircon chemistry indicates juvenile, Zr-saturated, mantle-derived alkaline melt (Hf 0.6–0.7 wt %, Y <0.2 wt %, U + Th + REE (Rare-Earth Elements) < 600 ppm, Zr/Hf 66–92, Eu/Eu*N ~1, positive Ce/Ce*N, HREE (Heavy REE) enrichment). Incompatible element depletion with increasing Yb/SmN from core to rim at ~ constant Hf suggests single stage growth. Ti-in-zircon temperatures (~570–740 °C) are lower than predicted by crystal morphology (800–900 °C) and decrease from core to rim (ΔT = 10–50 °C). The δ18O values (4.88 to 5.01‰ VSMOW (Vienna Standard Mean Ocean Water)) are relatively low for xenocrysts from the zircon Indo-Pacific zone (ZIP). The 176Hf/177Hf values (+ εHf 4.5–10.2) give TDepleted Mantle model source ages of 260–462 Ma and TCrustal ages of 391–754 Ma. The source magmas reflect variably depleted lithospheric mantle with little supracrustal input. Zircon U-Pb (0.88–1.56 Ma) and (U-Th)/He (0.86–1.02 Ma) ages are older than host basalt ages (~0.7 Ma), which suggests limited residence before transport. Zircon genesis suggests Zr-saturated, Al-undersaturated, carbonatitic-influenced, low-degree partial melting (<1%) of peridotitic mantle at ~60 km beneath the Indochina terrane. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email