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Transformation of scheelite M2MoTiO8 (M = Eu, Gd, Dy, Y) and zircon MVO4 (M = Ce, Sm, Gd, Dy) oxides to fluorite oxynitrides and perovskite oxides under mild ammonolysis conditions
摘要： Anion-deficient fluorite oxynitrides, M2MoTiO5-xN2+x-δ (M = Eu, Gd, Dy, Y; x = 0.0-0.2; δ (anion vacancies) = 0.2-0.4) have been synthesized by the reaction of single phase scheelite, M2MoTiO8 precursors with nitrogen enriched ammonia gas at 800-850 °C. The oxynitrides were characterized by elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), magnetic susceptibility and X-ray photoelectron spectroscopy (XPS) measurements. The results suggested that the products crystallizing in fluorite structure with an average oxidation state of Mo varying between 5.5-5.8 without any change in Ti4+ state. Similar attempts to react MVO4 (M = Ce, Sm, Gd, Dy), zircon oxides resulted only in V3+ containing perovskite (MVO3) oxides. The extent of nitrogen incorporation to form oxynitrides varies depending upon the stabilization of oxides in lower oxidation states.
关键词： GdVO3 perovskite,Fluorites,Scheelite,Ammonolysis,Oxynitrides,Zircon
更新于2025-09-23 15:23:52
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Calculating the Minimum Thickness of Glass Fuse by Zr Kα Line for Phosphorus-Containing Zircon-Refractory Material
摘要： In this paper, we take Zr Kα line as the analysis object due to the existence of overlapping phenomenon, which the zirconium La line (0.607nm) and phosphorus Ka line (0.615nm), in phosphorus-containing zircon-refractory material. We discovered and calculated the critical thickness of glass fuse by the theoretical calculation method, and we verified the feasibility of the theory. By experiment we found that critical thickness of glass fuse can be reduced by adding additives in flux. Conventional thickness of glass fuse can reaches a critical thickness by adding 20% of calcium oxide (in the form of calcium carbonate was added) in flux. This method could also increase significantly the measurement sensitivity to guarantee good result.
关键词： Zircon-refractory material,Minimum thickness,Zr Kα line
更新于2025-09-23 15:22:29
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Zircon fissiona??track and Ua??Pb double dating using femtosecond laser ablationa??inductively coupled plasmaa??mass spectrometry: A technical note
摘要： We present a new LA–ICP–MS system for zircon fission-track (FT) and U–Pb double dating, whereby a femtosecond laser combined with galvanometric optics simultaneously ablates multiple spots to measure average surface U contents. The U contents of zircon measured by LA–ICP–MS and standardized with the NIST SRM610 glass are comparable to those measured by the induced fission track method, and have smaller analytical errors. LA–ICP–MS FT dating of seven zircon samples including three IUGS age standards is as accurate as the external detector method, but can give a higher-precision age depending on the counting statistics of the U content measurement. Double dating of the IUGS age standards gives FT and U–Pb ages that are in agreement. A chip of the Nancy 91500 zircon has a homogeneous U content of 84 ppm, suggesting the possibility of using this zircon as a matrix-matched U standard for FT dating. When using the Nancy 91500 zircon as a U standard, a zeta calibration value of 42–43 yr cm?2 for LA–ICP–MS FT dating is obtained. While this value is strictly only valid for the particular session, it can serve as a reference for other studies.
关键词： dating,femtosecond laser,U–Pb,fission track,zircon,LA–ICP–MS
更新于2025-09-23 15:21:01
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Synthesis of high-purity zircon, zirconia, and silica nanopowders from local zircon sand
摘要： High-purity zircon (ZrSiO4) nanopowder was successfully produced from Indonesian natural zircon sand using a low-cost purification approach via magnetic separation, immersion in HCl, and reaction with NaOH, followed by a top-down nanosizing process using wet ball-milling for 10 hours and annealing at 200 °C for 2 hours. Furthermore, polymorph zirconia (ZrO2 – amorphous, tetragonal, and monoclinic) and silica (SiO2 – amorphous and cristobalite) nanopowders were also successfully derived from the purified zircon powder using a bottom-up method via alkali fusion and co-precipitation processes followed by calcination. The crystallite size of the powders was estimated from X-ray diffraction (XRD) data analysis to give 40, 31, 61, and 149 nm, respectively, for the zircon, tetragonal- and monoclinic-zirconia, and cristobalite. Microstructural characteristics of the zircon, silica, and zirconia nanopowders were revealed in transmission electron microscopy (TEM) images which confirmed that the average sizes of the particles were in a good agreement with the XRD estimated values.
关键词： zircon,tetragonal zirconia,amorphous silica,nanopowder,cristobalite,monoclinic zirconia
更新于2025-09-23 15:19:57
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Chemical analysis of a lunar meteorite by laser ablation mass spectrometry
摘要： The lunar meteorite Sayh al Uhaymir 169, that contains KREEP rich material, was investigated with our miniature laser ablation time-of-flight mass spectrometer to simulate the expected performance of in-situ measurements on the surface of a planetary body. The abundances of the major elements on the KREEP part of the rock were measured and plotted on a two-dimensional surface map to identify different mineral phases in the sample. The element distribution maps reveal the grain boundaries and allow identification of individual minerals and their major and trace element compositions. In the second measurement campaign the instrument was coupled with a HV pulser to increase sensitivity of the measurements. It could be shown that the detection sensitivity for heavy trace elements can be significantly improved while removing light elements from the analyzed ion beam. This study provides also measurements of U, Th and Pb elements present inside a single zircon grain. With the abundances of U and Pb in the zircon grain a preliminary age estimation of the zircon could be made and was found to be in reasonable agreement with ages reported in literature. Moreover, from the Ti concentration in the zircon grain a crystallization temperature was derived. Thus, by employing such an instrument on a planetary surface, scientific useful in-situ measurements on the element composition, the mineralogy, petrology and dating of surface samples can be accomplished.
关键词： Lunar meteorite,Trace elements,Laser ablation mass spectrometry,Crystallization temperature,KREEP material,Zircon
更新于2025-09-12 10:27:22
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[IEEE 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Xi'an, China (2019.6.19-2019.6.21)] 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - A Novel Power Decoupling Circuit in Paralleled with AC Side in Photovoltaic Micro-Inverter
摘要： The Neoproterozoic Tonian strata (ca. 870e725 Ma) in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South China Continent. These strata are separated into the basement and cover sequences by a regional angular unconformity. The basement sequence can be subdivided into the lower and the upper parts by the widespread interbedded ca. 840 Ma basalt with pillow structure. In the present work, 234 concordant detrital zircon analyses are obtained from three Tonian sandstone samples in the Fanjingshan district, Guizhou Province. Combined with previous results, a total of 1736 analyses of detrital zircon U-Pb ages derived from 12 formations of Tonian strata in the western Jiangnan Orogen are used to decipher the integrated sedimentary and tectonic histories. The zircons from the lowermost part of the basement sequence (the Yujiagou Formation) show oval morphology and display two Paleoproterozoic age peaks at 2325 Ma and 1845 Ma which are similar with the detrital zircon age peaks from the Late Paleoproterozoic to Early Mesoproterozoic Dongchuan/Dahongshan/Hekou groups, suggesting a passive margin basin in which the sediments were mainly sourced from the southwestern Yangtze Block. However, the zircon age population of the lower part of the basement sequence (the Xiaojiahe, Huixiangping formations and their equivalents) indicates the sedimentary derivation from bidirectional sources (the ca. 870 Ma arc materials in the south and the old detritus from the southwestern Yangtze Block) which is consistent with a back arc setting for the deposition of the sediments. Zircons from the upper part of the basement sequence (the Duyantang Formation and its equivalent) show euhedral and subangular morphology and display a unimodal age peak at ca. 835 Ma. This sequence was possibly deposited in a convergent setting and the detritus were came from the locally distributed syn-collisional igneous rocks. The lower part of the cover sequence (the Xinzhai and Wuye formations and their equivalents) shows a distinct zircon age peak at 815e809 Ma and two subordinate peaks at 2485 Ma and 2018 Ma, suggesting that the basin had gradually transformed into a continental rift basin and received the detritus from the ca. 815 Ma post-collisional magmatic rocks as well as from different Paleoproterozoic source rocks in the northern Yangtze Block. We propose a tectonic evolution model that envisages eruption of ca. 840 Ma basalt in a back arc basin that existed during ca. 870e835 Ma, an angular unconformity was formed during amalgamation of the Yangtze Block and the Cathaysia Block at ca. 835 e820 Ma and the rifting of the South China Continent was initiated at ca. 800 Ma. Our study concludes that the South China Continent was formed on the periphery of the Rodinia supercontinent.
关键词： Detrital zircon,Fanjingshan,Precambrian,Tonian,Sibao,Back arc basin
更新于2025-09-11 14:15:04
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by means of high-pressure–high-temperature Raman experiments
摘要： We report here high-pressure–high-temperature Raman experiments performed on BiVO4. We characterized the fergusonite and scheelite phases (powder and single crystal samples) and the zircon polymorph (nanopowder). The experimental results are supported by ab initio calculations, which, in addition, provide the vibrational patterns. The temperature and pressure behavior of the fergusonite lattice modes reflects the distortions associated with the ferroelastic instability. The linear coefficients of the zircon phase are in sharp contrast to the behavior observed in the fergusonite phase. The boundary of the fergusonite-to-scheelite second-order phase transition is given by TF ?Sch(K) = ?166(8)P (GPa) + 528(5). The zircon-to-scheelite, irreversible, first-order phase transition takes place at TZ?Sch(K) = ?107(8)P (GPa) + 690(10). We found evidence of additional structural changes around 15.7 GPa, which in the downstroke were found to be not reversible. We analyzed the anharmonic contribution to the wave-number shift in fergusonite using an order parameter. The introduction of a critical temperature depending both on temperature and pressure allows for a description of the results of all the experiments in a unified way.
关键词： zircon,scheelite,BiVO4,fergusonite,high-temperature,phase transition,high-pressure,ab initio calculations,Raman experiments,vibrational patterns
更新于2025-09-09 09:28:46