INORGANIC CHEMISTRY
·
2016
·
IF 4.82
Hui Yang,Chun-Li Hu,Jiang-Gao Mao
The first examples of mixed-anion lanthanide galloborates, namely, Ln2Ga[B3O6(OH)]2[B7O9(OH)2](CH3CO2)2 [Ln = Y (1), Sm (2), Eu (3), Gd (4), Dy (5)], have been obtained through hydrothermal synthesis. The title compounds are isomorphic and belong to monoclinic space group C2/c (No. 15). Their structures possess [B7O13(OH)2] borate layers further bridged with [B3O7] clusters to give a three-dimensional (3D) borate framework displaying two types of rhombus-like B14O14 14-membered-ring (14-MR) channels along the b axis. The Ga3+ ions are octahedrally coordinated and located at one end of the B14O14 14-MR channels, forming small tunnels of B7Ga 8-MRs, which are filled by the LnIII ions. The Ln ions and Ga cations are further held together by bridging acetate anions. It is worth noting that in these compounds there are two different types of borate clusters and two types of anions that are uncommon in the borates reported. Luminescent studies revealed the characteristic emission bands of Ln ions for compounds 2–5, and the luminescent lifetimes are 3.6, 0.86, and 3.05 ns for compounds 2, 3, and 5, respectively. Magnetic measurements suggest that there are antiferromagnetic interactions between magnetic centers for compounds 2–5.
研究领域:
材料科学
·
无机化学
✓ 已验证
DOI
高影响因子
JOURNAL OF LUMINESCENCE
·
2018
·
IF 2.732
Wenzhi Wang,Jinkai Li,Zhengyang Zhang,Zongming Liu
The new systems of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 ( x = 0–0.1) and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 ( y = 0–0.2) phosphors have been successfully obtained using the hydrothermal method at 900 °C in this work. The crystal structure, morphology, PL/PLE spectra, fluorescence and decay analysis have been studied in detail via the combined techniques of XRD , FE-SEM, PLE/PL spectra and decay kinetic. The phase-pure of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 with good dispersions have been formed at the lower sintering temperature of 900 °C. Under 273 nm and 270 nm excitation (the 6 P 7/2 → 8 S 7/2 transitions of Gd 3+ ), the Gd 2 (WO 4 ) 3 :Dy 3+ /Tb 3+ and Gd 2 (WO 4 ) 3 :Dy 3+ /Eu 3+ phosphors exhibit both Dy 3+ (yellow, at 574 nm) and Tb 3+ (green, at 547 nm) as well as Dy 3+ (yellow, at 574 nm) and Eu 3+ (red, at 616 nm) emissions, respectively. The presences of WO 4 2- , Gd 3+ and Dy 3+ excitation bands on the PLE spectra by monitoring the Tb 3+ and Eu 3+ emissions directly provide an evidence of energy transfer of WO 4 2- →Tb 3+ , Gd 3+ →Tb 3+ and Dy 3+ →Tb 3+ , as well as WO 4 2- →Eu 3+ , Gd 3+ →Eu 3+ and Dy 3+ →Eu 3+ , respectively. The quenching concentrations of both two systems are determined to be 7 at% ( x = 0.07 for Tb 3+ ) and 10 at% ( y = 0.10 for Eu 3+ ), and the quenching mechanisms of both two systems are mainly due to the Tb 3+ -Tb 3+ and Eu 3+ -Eu 3+ energy transfers, respectively. The color-tunable emission can be achieved though adjusting the relative content ratios of Dy 3+ /Tb 3+ or Dy 3+ /Eu 3+ , which has been verified by the CIE chromaticity coordinates analysis. The energy transfer efficiencies of Dy 3+ →Tb 3+ and Dy 3+ →Eu 3+ have been calculated, and the energy transfer mechanisms have been analyzed in detail. The (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 phosphors with color-tunable emission may have a potential application for w-LEDs.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2021
·
IF 5.816
Wenjie Yang,Chao Han,Yuehua Li,Huizhu Zhou,Shan Liu,Ling Wang,Zhangxing He,Lei Dai
BaHf 0.8 Ln 0.2 O 3-δ doped with rare earth elements with different ionic radii (Ln = Yb , Y, Dy and Gd) as candidate materials for solid oxide fuel cells and H 2 separation membrane have been prepared. Their phase composition , sinterability , chemical stability and conductivity were studied systematically. The rare earth elements are successfully incorporated into the main phase crystal lattice of barium hafnate to generate a single perovskite phase. The relative density of all samples sintered at 1600 °C reaches above 90%, and Y-doped BaHfO 3 has the highest relative density (94.7%) and the biggest grain size (about 1 μm) among all samples. The conductivities of the samples firstly increase and then decrease with the increase of the doped ion radius. Among all samples the conductivity of BaHf 0.8 Y 0.2 O 3-δ is the highest and reaches 6.02 × 10 −3 S cm −1 in wet air at 700 °C, which is attributed to the good sinterability and suitable crystal structure (tolerance factor and free volume). All samples also show excellent chemical stability in the test atmospheres, including saturated H 2 O steam, pure H 2 and CO 2 , 200 ppm H 2 S/Ar and boiling water. The Pt/BaHf 0.8 Y 0.2 O 3-δ electrolyte/Pt single cell was fabricated with a 530 μm-thick disk and its electrochemical properties were tested. The peak power density reaches 10.21 mW cm −2 at 700 °C, which is comparable to similar fuel cells reported. These results suggest that BaHf 0.8 Y 0.2 O 3-δ is a promising electrolyte candidate for proton-conducting fuel cells.
研究领域:
材料科学
·
能源工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF SOLID STATE CHEMISTRY
·
2025
·
IF 3.5
Xiaohui Li,Pengjun Zhao,Wenwen Kong,Aimin Chang,Bo Gao
Understanding electrical transport mechanisms and key thermal stability factors in high-temperature thermosensitive ceramics is essential for developing highly stable temperature sensors under extreme thermal conditions. This study develops the high-entropy pyrochlore stannates (La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 M 0.2 ) 2 Sn 2 O 7 (M = Eu, Dy, Ho, or Yb) via solid-state synthesis, demonstrating exceptional negative temperature coefficient (NTC) behavior across 300 – 1400 °C. Hall measurements and X-ray photoelectron spectroscopy (XPS) analyses reveal a dual redox mechanism for these ceramics: partial reduction of Sn 4+ to Sn 2+ at B-sites and rare-earth ions (Sm/Eu/Yb) to RE 2+ at A-sites, generating hole-dominated p-type conductivity. The materials exhibit outstanding thermal stability, with resistance drift below 1.96% after 500 hours at 1400 °C, attributed to the entropy-stabilized structure that effectively suppresses lattice disorder transformation. Aging studies further demonstrate that high oxygen vacancy concentrations lead to resistance drifts, as oxygen filling at elevated temperatures oxidizes RE 2+ to RE 3+ , reducing charge carriers and ultimately increasing resistivity. This study elucidates for the first time the hole-dominated conduction mechanism arising from dual-site cation valence changes (Sn/RE) and the regulation effect of oxygen vacancies on high-temperature stability, which provides an important theoretical basis and material design strategy for the development of the next-generation high-temperature NTC sensors with excellent stability.
研究领域:
材料科学
·
陶瓷材料
·
电气工程
·
固态物理
·
热传感器
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2025
·
IF 6.3
Jingfang Tong,Weijie Lin,Ruixin Guo,Zhongzheng Deng,Haitao Zhou,Shu Guo,Xiaojun Kuang
Strong magnetic anisotropy in low-dimensional magnets leads to a significant rotating magnetocaloric effect, presenting new opportunities for the exploration of more efficient and streamlined refrigeration systems. In this study, we have successfully synthesized a series of centimeter-scale rare-earth-containing fluorocarbonates, K 4 RE 2 (CO 3 ) 3 F 4 ( RE = Ce, Pr, Nd, Sm, Eu, Tb, and Dy) through a supercritical hydrothermal method, featuring unique RE 2 O 12 F 4 magnetic dimers. The above materials' fundamental magnetism has been systematically investigated, and no long-range magnetic transitions were captured above 1.8 K. Based on the low-temperature specific heat results, the long-range magnetic ordering was found around 0.84 K and 0.97 K for K 4 Tb 2 (CO 3 ) 3 F 4 and K 4 Dy 2 (CO 3 ) 3 F 4 , respectively. Furthermore, the anisotropic magnetism of K 4 Tb 2 (CO 3 ) 3 F 4 and K 4 Dy 2 (CO 3 ) 3 F 4 reveals significant magneto-crystalline anisotropy, with the magnetic field ( B ) aligned along the RE 2 O 12 F 4 magnetic dimer, which acts as the easy magnetic axis. The maximum rotating field entropy change, − Δ S R max for K 4 Tb 2 (CO 3 ) 3 F 4 reaches approximately 9 J kg -1 K -1 around 17 K, while for K 4 Dy 2 (CO 3 ) 3 F 4 , it is approximately 5.5 J kg -1 K -1 near 11 K, both under a 7 T field applied along the c -axis. These findings highlight the potential of these compounds for magnetic refrigeration applications through a rotating crystallographic direction.
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Yaochen Si,Lingfeng Li,Ruida Wang,Songting Zhang,Yingnan Cao,Hongyu Li,Shixian Zhao,Hongxia Li,Jing Feng
With the development of high power and high thrust-weight ratio aeronautics and astronautics, aircraft engines and gas turbine technology, the development of thermal barrier coating (TBCs) material is an enormous challenge, which requires both high temperature stability and resistance to molten calcium-magnesium-aluminosilicate (CMAS) corrosion. In this study, five high-entropy rare-earth tantalate (5RE 0.2 )TaO 4 (Re=Y, Gd, Dy, Ce, Sm, La, Yb) ceramics were prepared by high temperature solid state reaction. The phase composition, microstructure, thermophysical and mechanical properties and CMAS corrosion resistance of the obtained high-entropy (5RE 0.2 )TaO 4 ceramics were systematically investigated. The as-prepared five high-entropy rare-earth tantalate (5RE 0.2 )TaO 4 ceramics had monoclinic structure and uniform composition. The five (5RE 0.2 )TaO 4 ceramics all had lower Young’s modulus (135.06∼158.63 GPa), Vickers hardness (3.7∼6.2 GPa), fracture toughness (2.30-2.80 MPa·m 1/2 ) and brittleness index (1.45-2.53 μm –1/2 ) than that of YSZ. The thermal expansion rate and thermal expansion coefficients of the five (5RE 0.2 )TaO 4 ceramics were close to each other but showed higher value than that of single RETaO 4 (RE= Gd, Dy, Sm or Y) and lower value than that of YSZ. The thermal diffusivities and thermal conductivity of the five (5RE 0.2 )TaO 4 ceramics were lower than that of YSZ, YTaO 4 and GdTaO 4 at all temperature. During molten CMAS corrosion, CMAS melt diffused into the (5RE 0.2 )TaO 4 ceramics and then corroded (5RE 0.2 )TaO 4 grains, thereby forming a corrosion area composed of reaction layer and penetration layer. The CaO in penetrated CMAS melt could react with Ta element in (5RE 0.2 )TaO 4 ceramics to generate Ca 2 Ta 2 O 7 in the reaction layer and reduce the content of CaO in the penetrated CMAS melt, which increased the viscosity of the CMAS melt and inhibited the further penetration of CMAS into the ceramics. Based on the obtained results, the CMAS corrosion of (5RE 0.2 )TaO 4 ceramics was primarily controlled by the Ca 2 Ta 2 O 7 formation and the CMAS penetration.
研究领域:
材料科学
·
航空工程
✓ 已验证
产品关联
DOI
高影响因子
Materials Chemistry Frontiers
·
2022
·Vol. 7
·期 1
·168-182
·
IF 8.683
Peiran Huang,Zuhui Wen,Yue Yu,Jingyi Xiao,Zhanhua Wei,Tianshuai Lyu
X-Ray or 254 nm UV-light charged storage phosphors have various promising applications such as in anti-counterfeiting and information storage. However, developing such storage phosphors with high charge carrier storage capacity remains challenging. In this work, photoluminescence spectroscopy, thermoluminescence (TL), and vacuum-referred binding energy (VRBE) diagram were combined to study the trapping and liberation processes of charge carriers in Bi3+ and/or Ln3+ (Ln = Tb, Pr, or Dy) doped LiLuGeO4. Unintended defects act as good electron trapping centers, while Bi3+, Tb3+, and Pr3+ act as hole-capturing and recombination centers. Dy3+ does not act as an electron trapping center but as a luminescence center by energy transfer from Bi3+ → Dy3+. The ratios of the integrated TL intensities between 303 K and 650 K for LiLuGeO4:0.005Bi3+, LiLuGeO4:0.005Bi3+,0.005Tb3+, or LiLuGeO4:0.005Bi3+,0.005Dy3+ after X-ray charging to that of the state-of-the-art BaFBr(I):Eu2+ is about 1.24, 0.59, and 0.90, respectively. More than 10 h or 40 h afterglow was measurable in both LiLuGeO4:0.005Bi3+ and LiLuGeO4:0.005Bi3+,0.005Tb3+ after X-ray or 254 nm UV-light charging. The stored charge carriers stored can be efficiently excited to produce optically stimulated luminescence with a wide range 365 nm UV-light to 850 nm infrared laser beam. Proof-of-concept colour-tailorable afterglow, X-ray irradiation time or sample mass-dependent dosimetry, and optically-stimulated luminescence with a wide range of 365 nm UV-light to 850 nm infrared laser stimulation will be demonstrated for anti-counterfeiting, information storage, and display applications in the developed Bi3+ and/or Ln3+-doped LiLuGeO4. This work not only reports Bi3+ and/or Ln3+ doped LiLuGeO4 storage phosphors with excellent charge carrier storage capacity but also deepens our understanding of the afterglow and storage phosphors and luminescence mechanisms, which can guide us to explore new afterglow and storage phosphors for multimode applications.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2024
·
IF 5.8
Jiadong Hou,Yufeng Liu,Chufei Cheng,Fuhao Cheng,Pengfei Qin,Yang Miao,Weihua Ji,Xiaomin Wang
The limited efficiency of traditional trial-and-error experiments has impeded the development and application of high-entropy fluorite oxides in thermal insulation coatings. To solve this problem, a novel entropy descriptor based on first principles is presented to help select candidate components for synthesizing high-entropy fluorite structure oxides. Results show that the compatibilities of 10 single-phase high-entropy fluorite oxides can be accurately predicted based on entropy formation ability. In the studied (Zr, Hf, Pr, La, X) O 2-δ system, a correlation between thermal characteristics and size/mass differences was established by designing the size and mass of X. Specifically, we found that the thermal conductivity is more strongly correlated with the difference in atomic mass, while the coefficient of thermal expansion is strongly correlated with the difference in atomic size. X-ray photoelectron spectroscopy (XPS) analysis shows that the concentration of oxygen vacancy can effectively reduce the thermal conductivity of high-entropy fluorite oxides. In addition, the values of hardness, elastic modulus and thermal conductivity of five single-phase fluorite oxides are successfully predicted by first principles calculation , and the differences between these values and the experimental results are small, which provides a prospective significance for the performance prediction of high-entropy fluorite oxides. Our findings provide a strategy for customizing high-entropy fluorite single-phase oxides with suitable properties to meet the performance requirements of thermal barrier coatings (TBCs).
研究领域:
材料科学
·
热力学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）