Phase stability of rare earth sesquioxides with grain size controlled in the nanoscale

2019 ◽  
Vol 102 (7) ◽  
pp. 3829-3835 ◽  
Author(s):  
Giora Kimmel ◽  
Roni Z. Shneck ◽  
Witold Lojkowski ◽  
Ze'ev Porat ◽  
Tadeusz Chudoba ◽  
...  
Keyword(s):  
Grain Size ◽  
Rare Earth ◽  
Phase Stability ◽  
Rare Earth Sesquioxides ◽  
Size Controlled

Revised phase stability diagram of rare earth sesquioxides

2020 ◽  
pp. 1-2
Author(s):  
Giora Kimmel ◽  
Witold Lojkowski ◽  
Roni Z Shneck
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Surface Energy ◽  
Phase Stability ◽  
Monoclinic Phase ◽  
Stability Diagram ◽  
Stable Structure ◽  
Stable Phase ◽  
Cubic Phase ◽  
Rare Earth Sesquioxides

Below 2000°C rare earth sesquioxides (RESOX) have three crystal structures: hexagonal, cubic and monoclinic, designated as A, C and B respectively [1-3]. Early studies, based on low temperature (LT) synthesis, suggested that RESOX phase stability versus temperature is a function of the metallic ion radii (MIR). La2 O3 Ce2 O3 and Nd2 O3 with the highest MIR are A-type, while for Sm2 O3 , Eu2 O3 and Gd2 O3 with intermediate MIR the structure is C-type at LT and B-type at high temperature (HT) [1-3]. All other RESOX including Y2 O3 and Sc2 O3 were assumed to be cubic (C-type) at all temperatures below 2000°C. The transformation from LT cubic to high temperature (HT) monoclinic structure in Sm2 O3 , Eu2 O3 and Gd2 O3 is unusual and therefore Brauer [4] and Yokogawa et al. [5] suggested that the stable phase is monoclinic at all temperatures below 2000°C. To resolve the controversy, we have demonstrated that slowing down grain growth of Sm2 O3 and Gd2 O3 [9] prevented transition from C to B-types in the expected temperatures (1100 and 1300°C respectively). Hence, we suggest that the surface energy plays an important role in determining the structure of nanomaterials [6,7]. The monoclinic Sm2 O3 , Eu2 O3 and Gd2 O3 is the stable structure at all temperatures below 2000 °C when the grain size is large in the nanoscale. However, for smaller nanocrystals the stable structure is cubic since it has a lower surface energy than the monoclinic phase. In addition, Kimmel et al. [9] suggested that for all RESOX with MIR lower than Gd3+ (except Sc2 O3 ) obtained by HT synthesis [10-17] or under high pressure [18-20] the monoclinic phase is the stable phase also at LT. Figure 1 shows the transition from LT monoclinic to the HT cubic phase according to Sato et al. [17]. Figue 2 shows the suggested RESOX stability diagram as function of temperature versus MIR. In sol-gel production the formation of C-type structures is due to the formation of nano-crystals. Subsequent firing at high temperatures yields the HT cubic phase. Thus. the assumption of a continuous cubic structure at all temperatures is wrong. As seen in Figure 1, in Sc2 O3 the monoclinic to cubic transition is below room temperature, in agreement with the fact that HT synthesis yields cubic Sc2 O3 [17]. (The ion radius of Sc3+ is 0.087 nm [21,22])

Preferential Orientation of Photochromic Gadolinium Oxyhydrides

2020 ◽  
Author(s):  
Elbruz Murat Baba ◽  
Jose Montero ◽  
Dmitrii Moldarev ◽  
Marcos V. Moro ◽  
Max Wolff ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Rare Earth ◽  
Preferential Orientation ◽  
Reactive Magnetron ◽  
Flow Ratio ◽  
Deposition Pressure ◽  
Step Process ◽  
Oxidation In Air ◽  
Key Parameter

<p>We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH<sub>2-x</sub>) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations, and photochromic response of the films are strongly dependent on the deposition pressure. GdHO films show preferential orientation along the [100] direction and exhibit photochromism when synthesized at deposition pressures up to 5.8 Pa and. The photochromic contrast is larger than 20 % when the films are deposited below 2.8 Pa with 0.22 H<sub>2</sub>/Ar flow ratio. We argue that the degree of preferential orientation defines the oxygen concentration which is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above are explained by the oxidation-induced decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas. </p>

scholarly journals Self-assembly induced luminescence of Eu3+-complexes and application in bioimaging

2021 ◽  
Author(s):  
Ping-Ru Su ◽  
Tao Wang ◽  
Pan-Pan Zhou ◽  
Xiao-Xi Yang ◽  
Xiao-Xia Feng ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Rare Earth ◽  
Luminescence Intensity ◽  
Self Assembly ◽  
Room Temperature ◽  
Molecular Motion ◽  
Proof Of Concept ◽  
Room Temperature Phosphorescence ◽  
New Strategy ◽  
Size Controlled

Abstract Design and engineering of highly efficient emitting materials with assembly-induced luminescence, such as room temperature phosphorescence (RTP) and aggregation-induced emission (AIE), have stimulated extensive efforts. Here, we propose a new strategy to obtain size-controlled Eu3+-complex nanoparticles (Eu-NPs) with self-assembly induced luminescence (SAIL) characteristics without encapsulation or hybridization. Compared with previous RTP or AIE materials, the SAIL phenomena of increased luminescence intensity and lifetime in aqueous solution for the proposed Eu-NPs are due to the combined effect of self-assembly in confining the molecular motion and shielding the water quenching. As a proof of concept, we also show that this system can be further applied in bioimaging, temperature measurement and HClO sensing. The SAIL activity of the rare-earth (RE) system proposed here offers a further step forward on the roadmap for the development of RE light conversion systems and their integration in bioimaging and therapy applications.

scholarly journals Effect of Rare Earth Ce on Deep Stamping Properties of High-Strength Interstitial-Free Steel Containing Phosphorus

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1473
Author(s):  
Hao Wang ◽  
Yanping Bao ◽  
Chengyi Duan ◽  
Lu Lu ◽  
Yan Liu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Rare Earth ◽  
High Strength ◽  
Rolling Process ◽  
P Element ◽  
Second Phase ◽  
Strengthening Effect ◽  
Interstitial Free ◽  
If Steel

The influence of rare earth Ce on the deep stamping property of high-strength interstitial-free (IF) steel containing phosphorus was analyzed. After adding 120 kg ferrocerium alloy (Ce content is 10%) in the steel, the inclusion statistics and the two-dimensional morphology of the samples in the direction of 1/4 thickness of slab and each rolling process were observed and compared by scanning electron microscope (SEM). After the samples in each rolling process were treated by acid leaching, the three-dimensional morphology and components of the second phase precipitates were observed by SEM and energy dispersive spectrometer (EDS). The microstructure of the sample was observed by optical microscope, and the grain size was compared. Meanwhile, the content and strength of the favorable texture were analyzed by X-ray diffraction (XRD). Finally, the mechanical properties of the product were analyzed. The results showed that: (1) The combination of rare earth Ce with activity O and S in steel had lower Gibbs free energy, and it was easy to generate CeAlO3, Ce2O2S, and Ce2O3. The inclusions size was obviously reduced, but the number of inclusions was increased after adding rare earth. The morphology of inclusions changed from chain and strip to spherical. The size of rare earth inclusions was mostly about 2–5 μm, distributed and dispersed, and their elastic modulus was close to that of steel matrix, which was conducive to improving the structure continuity of steel. (2) The rare earth compound had a high melting point. As a heterogeneous nucleation point, the nucleation rate was increased and the solidification structure was refined. The grade of grain size of products was increased by 1.5 grades, which is helpful to improve the strength and plasticity of metal. (3) Rare earth Ce can inhibit the segregation of P element at the grain boundary and the precipitation of Fe(Nb+Ti)P phase. It can effectively increase the solid solution amount of P element in steel, improve the solid solution strengthening effect of P element in high-strength IF steel, and obtain a large proportion of {111} favorable texture, which is conducive to improving the stamping formability index r90 value.

scholarly journals Geochemistry of Surface Sediments From the Emperor Seamount Chain, North Pacific

2021 ◽  
Vol 9 ◽  
Author(s):  
Jie Chen ◽  
Jianjun Zou ◽  
Aimei Zhu ◽  
Xuefa Shi ◽  
Dirk Nürnberg ◽  
...  
Keyword(s):  
Grain Size ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Water Depth ◽  
Surface Sediment ◽  
North Pacific ◽  
The North ◽  
Seamount Chain ◽  
The North Pacific ◽  
Emperor Seamount Chain

Investigating the composition and distribution of pelagic marine sediments is fundamental in the field of marine sedimentology. The spatial distributions of surface sediment are unclear due to limited investigation along the Emperor Seamount Chain of the North Pacific. In this study, a suite of sedimentological and geochemical proxies were analyzed, including the sediment grain size, organic carbon, CaCO3, major and rare earth elements of 50 surface sediment samples from the Emperor Seamount Chain, spanning from ∼33°N to ∼52°N. On the basis of sedimentary components, we divide them into three Zones (I, II, and III) spatially with distinct features. Sediments in Zone I (∼33°N–44°N) and Zone III (49.8°N–53°N) are dominated by clayey silt, and mainly consist of sand and silty sand in Zone II. The mean grain size of the sortable silt shows that the hydrodynamic condition in the study area is significantly stronger than that of the abyssal plain, especially at the water depth of 1,000–2,500 m. The CaCO3 contents in sediments above 4,000 m range from 20 to 84% but decrease sharply to less than 1.5% below 4,000 m, confirming that the water depth of 4,000 m is the carbonate compensation depth of the study area. Strong positive correlations between Al2O3 and Fe2O3, TiO2, MgO, and K2O (R &gt; 0.9) in the bulk sediments indicate pronounced contributions of terrigenous materials from surrounding continent mass to the study area. Furthermore, the eolian dust makes contributions to the composition of bulk sediments as confirmed by rare earth elements. There is no significant correlation between grain size and major and minor elements, which indicates that the sedimentary grain size does not exert important effects on terrigenous components. There is significant negative δCe and positive δEu anomalies at all stations. The negative Ce anomaly mainly exists in carbonate-rich sediments, inheriting the signal of seawater. The positive Eu anomaly indicates widespread volcanism contributions to the study area from active volcanic islands arcs around the North Pacific. The relative contributions of terrestrial, volcanic, and biogenic materials vary with latitude and water depth in the study area.

Electronic structure of rare-earth sesquioxides and oxysulfides

2006 ◽  
Vol 408-412 ◽  
pp. 687-692 ◽  
Author(s):  
Masayoshi Mikami ◽  
Shinichiro Nakamura
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Rare Earth Sesquioxides
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