Fine-Grained Tungstates SrWO4 and NaNd(WO4)2 with the Scheelite Structure Prepared by Spark Plasma Sintering
摘要:
Fine-grained SrWO4 and NaNd(WO4)(2) ceramics with the scheelite structure having high relative densities (99 and 95.8%), which can appear candidate matrices for radioactive waste (RAW) management, are prepared by spark plasma sintering (SPS). The phase identity of the ceramics is determined by X-ray powder diffraction; their microstructure is studied by X-ray photoelectron spectroscopy. The tungstates under study are sintered at rather low temperatures (580-665 degrees C). The intensity of compaction of the tungstates at the early sintering stage is determined by the degree of powder agglomeration. The activation energy of fine-grained scheelite ceramics at high temperatures corresponds with the activation energy of grain-boundary oxygen diffusion.
Iridium-Incorporated Strontium Tungsten Oxynitride Perovskite for Efficient Acidic Hydrogen Evolution
作者:Bingzhang Lu、Carolin B. Wahl、Xiao Kun Lu、Matthew E. Sweers、Haifeng Li、Vinayak P. Dravid、Linsey C. Seitz
DOI:10.1021/jacs.2c03617
日期:2022.8.3
diversity with adjustable electronic, magnetic, and optical properties that provide immense opportunities for materials design. Within this material family, perovskite oxynitrides incorporate earth-abundant nitrogen with differing size, electronegativity, and charge into oxide, enabling a unique approach to tuning metal-anion covalency and energy of metal cation electronic states, thereby achieving
杂阴离子材料表现出巨大的结构多样性,具有可调节的电子、磁性和光学特性,为材料设计提供了巨大的机会。在该材料家族中,钙钛矿氧氮化物将地球上丰富的具有不同尺寸、电负性和电荷的氮结合到氧化物中,从而实现了一种独特的方法来调节金属-阴离子共价和金属阳离子电子态的能量,从而实现其可能无法实现的功能。钙钛矿氧化物对应物,已作为电催化剂被广泛研究。然而,由于后过渡金属与 N 配位和/或高价态的热稳定性差,直接获得此类材料非常具有挑战性。在此处,我们引入了一种有效的策略来制备钙钛矿氧氮化物,其中一小部分位点被 Ir 取代,并将其作为该材料家族中的第一个电催化剂,从而实现了贵金属含量的高活性和高效利用。通过一系列表征技术,包括 X 射线吸收光谱、原子分辨率电子显微镜、X 射线光电子能谱和 X 射线衍射,我们证明了 Ir 成功地结合到锶钨氧氮化物钙钛矿结构中并发现了独特的 Ir-N/O 配位结构。受益于此,该
Observation of chemical reactions between alkaline-earth oxides and tungsten at high pressure and high temperature
作者:Daniel Errandonea
DOI:10.1016/j.jpcs.2009.06.009
日期:2009.7
Abstract The potential chemical reactions of alkaline-earth oxides (AeO with Ae: Mg, Ca, Sr, and Ba) and tungsten are studied at highpressure and high temperature. At pressures ranging from 5 to 10 GPa and temperatures of 2000 K, a noticeable reaction between AeO and powder tungsten (W) was detected. As a product of the reaction, scheelite-structured orthotungstates (AeWO 4 ) were formed. The reactivity
Luminescence of undoped and Eu<sup>3+</sup> doped nanocrystalline SrWO<sub>4</sub> scheelite: time resolved fluorescence complimented by DFT and positron annihilation spectroscopic studies
作者:Santosh K. Gupta、K. Sudarshan、P. S. Ghosh、K. Sanyal、A. P. Srivastava、A. Arya、P. K. Pujari、R. M. Kadam
DOI:10.1039/c5ra23876e
日期:——
Effect of annealing temperature on photophysical characteristics of pure and SrWO4:Eu3+ nanoparticles were investigated and the changes observed correlated with density function theory (DFT) and positron annihilation lifetime spectroscopy (PALS).
Low-temperature synthesis of homogeneous solid solutions of scheelite-structured Ca<sub>1−x</sub>Sr<sub>x</sub>WO<sub>4</sub> and Sr<sub>1−x</sub>Ba<sub>x</sub>WO<sub>4</sub> nanocrystals
作者:Sean P. Culver、Matthew J. Greaney、Antonio Tinoco、Richard L. Brutchey
DOI:10.1039/c5dt01722j
日期:——
prepared under benign synthesis conditions using the vapor diffusion sol–gel method. Discrete nanocrystals with sub-20 nm mean diameters were obtained after kinetically controlled hydrolysis and polycondensation at room temperature, followed by composition-dependent thermal aging at or below 60 °C. Rietveld analysis of X-ray diffraction data and Raman spectroscopy verified the synthesis of continuous and
一系列下式的组成复杂的白钨矿结构的纳米晶体的1- X甲' X WO 4(A =钙,锶,钡)具有使用蒸汽扩散溶胶-凝胶法合成良性条件下被制备。在室温下进行动力学控制的水解和缩聚反应,然后在60°C或低于60°C的温度下进行组分依赖的热老化后,可获得平均直径小于20 nm的离散纳米晶体。X射线衍射数据和拉曼光谱的Rietveld分析验证连续和相纯纳米晶体的固溶体的合成在整个组合物空间甲1- X甲' X WO 4,其中0≤X ≤1.元素通过X射线光电子和电感耦合等离子体-原子发射光谱分析表明标称和实验确定的元素的化学计量之间极好的一致性,而能量色散型X射线光谱法中说明的这些纳米晶体良性条件下合成的内良好的空间均匀性元素。
Scheelite-type MWO4 (M=Ca, Sr, and Ba) nanophosphors: Facile synthesis, structural characterization, photoluminescence, and photocatalytic properties
Scheelite-type MWO4 (M = Ca, Sr, and Ba) nanophosphors were synthesized by the precipitation method. All compounds crystallized in the tetragonal structure with space group 141/a (No. 88). Scherrer's and TEM results revealed that the average crystallite size varies from 32 to 55 nm. FE-SEM illustrate the spherical (CaWO4), bouquet (SrWO4), and fish (BaWO4) like morphologies. PL spectra indicate the broad emission peak maximum at 436 (CaWO4), 440 (SrWO4), and 433 nm (BaWO4) under UV excitation. The calculated CIE color coordinates of MWO4 nanophosphors are close to the commercial BAM and National Television System Committee blue phosphor. The photocatalytic activities of MWO4 were investigated for the degradation of methylene blue dye under UV illumination. At pH 3, BaWO4 nanocatalyst showed 100% dye degradation within 60 min. The photocatalytic activity was in the decreasing order of BaWO4> CaWO4>SrWO4 under both neutral and acidic conditions. (C) 2014 Elsevier Ltd. All rights reserved.