JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2012
·Vol. 95
·期 10
·3214-3219
·
IF 2.272
Haoyi Wu,Yihua Hu,Fengwen Kang,Nana Li,Guifang Ju,Zhongfei Mu,Zhongfu Yang
Praseodymium (Pr 3+ ) with rich f energy levels can generate various visible emissions, but the luminescence of Pr 3+ in a CaWO 4 matrix has not yet been studied. In this article, the phosphors of Pr 3+ -doped CaWO 4 were synthesized via a high temperature solid-state reaction, and the photoluminescence (PL) and afterglow properties of Pr 3+ in the CaWO 4 matrix were investigated. The phase identifications of the samples show that an impure monoclinic phase appears when the Pr 3+ concentration is high. The results of PL exhibit the usual Pr 3+ characteristic emissions as well as an emission that is produced by the charge transfer from 5 d of W 6+ to 2 p of O 2− under a shortwave ultraviolet excitation. An intermediate energy transfer occurs during the charge transfer which induces the afterglow. The quenching point of Pr 3+ in CaWO 4 is 2 mol%, corresponding to the critical energy transfer distance of ~20 Å. The quenching mechanism in the Pr 3+ -doped CaWO 4 is the dipole-dipole interaction. The Ca 2+ vacancies ( V Ca ) are the defects that induce the traps and capture holes from O 2− . The thermal energy of holes liberation from V Ca to O 2− results in the charge transfer accompanied by an energy transfer to Pr 3+ , and consequently generates the afterglow. The experimental results also show that the afterglow characteristics of Pr 3+ are prolonged by incorporating Pr 3+ in the CaWO 4 matrix.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Ruiheng Xiang,Huaicheng Xiang,Jie Li,Ying Tang,Liang Fang
The microwave dielectric properties of NdNbO 4 (NN) ceramics were optimized by substituting Ca 2+ at the A-site and W 6+ at the B-site. (1- x )NdNbO 4 - x CaWO 4 (NNCW x ) ( x = 0–0.3) ceramics crystallize in the monoclinic fergusonite structure (space group I 2/ a ), whereas NNCW-0.4 exhibits a tetragonal scheelite structure (space group I 4 1 / a ), suggesting that Ca 2+ /W 6+ doping effectively contributed to the ferroelastic phase transition. A near-zero temperature coefficient of resonant frequency ( τ f ) of +7.8 ppm/°C, a high Q × f value of 59,190 GHz, and a low permittivity ( ε r ) of 17.51 were obtained for the NNCW-0.3 ceramic. With the increase of x , the permittivity decreases gradually, while τ f shows the opposite trend. The permittivity is mainly affected by the polarizability per unit molar volume ( α / V m ) and the rattling effect of A-site cations (Nd 3+ and Ca 2+ ). The Q × f values of NNCW x ceramics are mainly affected by relative density, packing fraction, and lattice energy ( U ). The influencing mechanism of τ f is a combination of an increase in the temperature coefficient of ion polarizability ( τ αm ), lattice strain, and phase transition.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY
·
2020
·Vol. 35
·期 5
·886-895
·
IF 3.498
Yuqiu Ke,Jianzong Zhou,Xiaoqing Yi,Yijian Sun,Jianfeng Shao,Shiyong You,Wei Wang,Yunzhi Tang,Chaoyang Tu
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been widely used for in situ microanalysis of elemental concentrations in solid samples, but its application is hampered by a lack of matrix-matched and homogeneous reference materials (RMs). In this work, a new method for preparing matrix-matched and homogeneous LA-ICP-MS reference materials has been developed. A multiple rare earth element (REE) doped CaWO4 single crystal (CaW-1) was successfully prepared by the Czochralski technique. The matrix composition and crystal structure were confirmed by X-ray diffraction (XRD) and electron microprobe analysis (EMPA), which indicates that these crystals have a matrix composition of CaWO4 and are matrix-matched with natural scheelite. The homogeneity of REE distribution was systematically studied by seven methods and the results demonstrated that REEs are distributed homogeneously in the CaWO4 single crystal with slight fluctuation (RSDs: ca. 4%). It can be concluded that the synthesized CaWO4 single crystal meets both crucial requirements, matrix-matched and homogeneous distribution, for an LA-ICP-MS reference material, and therefore it was used to quantitatively calibrate REE concentrations in natural scheelite. The results showed that acceptable analytical errors (<8%) were obtained, which were more desirable than those obtained with non-matrix-matched NIST SRM 610 as the RM. It robustly validates the ability of the developed method for preparing CaWO4 single crystals as possible LA-ICP-MS reference materials to calibrate REE concentrations in natural scheelite.
研究领域:
矿物学
·
分析化学
✓ 已验证
DOI
高影响因子
GEOSTANDARDS AND GEOANALYTICAL RESEARCH
·
2023
·Vol. 47
·期 4
·773-792
·
IF 3.8
Yu Zhang,Shiyong You,Fuwen Tan,Jianfeng Shao,Jianzong Zhou,Tengfei Zheng,Wenxian Yi,Ping Xia,Lanlan Jin,Haitao Li,Ruixiang Wang,Herui Wen,Yuqiu Ke,Yijian Sun
In this work, we prepared three CaWO 4 single crystals (CaW-0, CaW-1 and CaW-3) doped with rare earth elements (REEs) at nominal mass fractions of 50, 250 and 5000 μg g -1 using the Czochralski method. Electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were employed to evaluate the within- and between-unit homogeneity of major elements and REEs, respectively. The within-unit variation ( s r ) of 0.40–0.84% and between-unit s r of 0.14–1.48% for major elements were obtained. Within- and between-unit s r of 0.53–5.56% were also found for REEs by LA-ICP-MS spot analyses. A comparison of the s r of repeat analyses was compared with the analytical uncertainty ( u ), i.e., the mean square weighted deviation (MSWD), which is close to or slightly higher than 1, indicating that no obvious chemical heterogeneity was found in these crystals. Reference values for these elements were obtained through various analytical methods across four different laboratories and applications of the reference materials to calibrating REE mass fractions in a natural scheelite were performed. No significant difference of the results was found as t values are less than 2.75 at the 99% confidence interval. The excellent linearity ( R 2 > 0.98) between the REE mass fractions and both LA-ICP-MS signal intensity and wafer absorbance was found, but the crater height and the absolute mass transported into ICP-MS decreased when REE mass fractions as well as the colour of crystals increased. These results suggest that the reference materials have the potential to calibrate REE mass fractions in natural scheelite.
研究领域:
矿物学
·
分析化学
✓ 已验证
DOI
高影响因子
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