Oxide Crystals Research Articles

Manufacturing technique for Jizhou painted porcelains in the Yuan dynasty and its influence on coloring

The Jizhou kiln was an important production center of the painted porcelains in Southern China during the Song and Yuan dynasties. The manufacturing technique of the painted porcelains in the Jizhou kiln potentially facilitated the emergence of the well-known blue-and-white porcelains in Jingdezhen. Herein, the chemical compositions and microstructures of the bodies, glazes and paintings of Jizhou painted porcelains from the Yuan dynasty were investigated through X-ray fluorescence (XRF), optical microscopy (OM), Raman spectroscopy and field emission scanning electron microscopy with energy dispersive spectroscopy (SEM‒EDS) to clarify the manufacturing characteristics of Jizhou painted porcelains and their impact on the coloring mechanism. The results showed that the bodies of Jizhou painted porcelains were made of local clay and those transparent glazes were made of local sericite-rich clay and botanic ashes. Black‒brown painted porcelains and red‒brown painted porcelains were methodically made by ancient potters by controlling pigment formulation, painting techniques and firing schedules. The colors of the black‒brown painting and the red‒brown painting were related to the α-Fe2O3 particles in the iron-rich minerals used in the pigment and the iron oxide crystals (α-Fe2O3 and ε-Fe2O3) precipitated on the glaze surface, respectively.

Performance Characteristics of a New-Generation Digital Bismuth Germanium Oxide PET/CT System, Omni Legend 32, According to NEMA NU 2-2018 Standards.

The Omni Legend 32 PET/CT system features silicon photomultiplier (SiPM)-based detectors with bismuth germanium oxide crystals and a 32-cm axial field of view (FOV). The present study aimed to determine the performance characteristics of the Omni Legend 32 PET/CT system according to National Electrical Manufacturers Association (NEMA) NU 2-2018 standards. Methods: The PET component of this system comprises 22 detector modules; each module contains 24 detector blocks with 72 bismuth germanium oxide crystals with a volume of 4.1 × 4.1 × 30 mm coupled to 18 SiPM devices with a 6 × 6 mm area, resulting in an axial FOV of 32 cm. The spatial resolution, sensitivity, count rate performance, and image quality delivered by PET were evaluated using the NEMA NU 2-2018 standard. PET images of 2 patients were evaluated to get a visual first impression of the Omni Legend 32 PET/CT system together with Precision DL. Results: The average spatial resolution at 1, 10, and 20 cm from the central axis was 4.3, 5.3, and 6.2 mm, respectively, for filtered backprojection and 3.7, 4.3, and 5.1 mm, respectively, for ordered-subset expectation maximization. The NEMA sensitivity was 47.30 and 47.05 cps/kBq at the axial center of the FOV and at a 10-cm radial offset, respectively. The scatter fraction, count rate accuracy, and peak noise-equivalent count rates were 35.4%, 1.7%, and 501.7 kcps, respectively, at 15.7 kBq/mL. Contrast recovery for the NEMA body phantom from the smallest to the largest sphere ranged from 61.3% to 93.0%, with a background variability of 5.4%-11.7% and a lung error of 5.1% for Q.Clear (β-value, 50). Good patient image quality was obtained with the Omni Legend 32. Conclusion: The Omni Legend 32 has class-leading sensitivity and count rates within the category of whole-body PET systems while maintaining spatial resolution broadly comparable to that of other current SiPM-based PET/CT systems. This combination of properties results in a very good image quality.

Effect of structural disorder on the oxidation of Zr-based amorphous alloys: A focused review

Structural disordering leads to outstanding mechanical properties of amorphous alloys. Many properties are strongly related to formation of surface oxide layers. An in-depth understanding of effect of structural disordering of amorphous alloys on oxide evolution is essential for applications. This paper presents a review of recent comparative oxidation studies of Zr-based amorphous and single-phase crystalline counterpart alloys. Three representative model alloy systems are selected: Zr–Cu and Zr–Al representing alloys with components of different and similar oxygen affinities, respectively, and Zr–Cu–Al representing multi-component alloys. In combination with molecular dynamic simulations, the fundamental role of the structural disordering of parent alloys in the oxidation processes is revealed. The oxidation of Zr–Cu–Al–Ni amorphous alloys at the supercooled liquid temperature region is further reviewed to clarify the relationship between oxidation and substrate crystallization.

Thermal, spectroscopy and optimized ∼3 µm CW laser properties for Ho,Pr:YAP crystal.

We demonstrate the thermal, spectroscopy and laser properties of Ho,Pr doped YAP crystal grown successfully by Cz method. The thermal expansion coefficient, thermal conductivity, absorption and emission spectra of Ho,Pr:YAP crystal are investigated in detail. Additionally, the level lifetimes suggest that Pr3+ is a suitable deactivating ion for Ho:YAP crystal. Particularly, the actual laser performance is optimized by doping active ion Ho with high concentrations and introducing deactivated Pr3+, resulting in decreased laser threshold, increased laser output power and slope efficiency. A 3.01 µm laser with output power of 502 mW, slope efficiency of 6.3% and beam quality factors of 1.42/1.43 is achieved in the Ho,Pr:YAP crystal, as far as we know this is the highest ∼3 µm CW laser power realized in Ho3+ doped oxide crystals.

Simultaneous synthesis of nanoporous zinc oxide and carbon dots via biopolymer dual templating

Dual templating is an effective strategy to create multiple inorganic functional materials with enhanced structural, optical, and biological properties. We demonstrate how biopolymer directly dictates the internal structure of zinc oxide. Here, a thermally degradable biopolymer, chitosan, is used as a structural template to produce internal nano pores of zinc oxide, while biopolymer transforms into highly luminescent carbon dots in the same solution. It is thought that zinc oxide is nucleated within the polymer network and continues to grow by engulfing the network into its crystalline structure. This is followed by thermal degradation of polymer template and its carbonisation into carbon dots. The synthesised porous zinc oxide-chitosan composites are characterised by PXRD, FT-IR, TGA, and SEM. The shape and size of pores created within zinc oxide crystals are assessed by FIB-SEM analysis. Finally, the antioxidant activity of the synthesised composites is significantly enhanced even at low concentrations from 20% in pure zinc-oxide to 100% in the synthesised composites.

The formation of V-doped Ti4O7 hollow Magnéli phase with improved electrical conductivity and thermal stability

Due to its excellent electrical conductivity and stable Magnéli phase structures, cermet Ti4O7 has emerged as one of the most promising materials in the fields of electrochemical application. However, the difficulties in creating high specific surface area structures, having room for conductivity enhancement when used as a conductive additive, and passivation forming TiO2 under sufficiently oxidizing conditions limit the development of Ti4O7 for practical applications. In this work, the V-doped Ti4O7 hollow spheres with improved electrical conductivity and thermal stability were synthesized by the three-step approach of solvothermal reaction, oxidative crystallization, and hydrogen reduction without any surfactant or template. The formation mechanism of hollow (Ti,V)4O7 was revealed by analyzing the valence evolution of V and comparing the morphology of Ti4O7. The conductivity of Ti4O7 and (Ti,V)4O7 was compared and contrasted as functions of pressure, demonstrating the superiority of (Ti,V)4O7 in terms of conductivity. Thermograms showed that the addition of V increased the complete oxidation temperature of Ti4O7. Moreover, the reason for the enhanced electrical conductivity and thermal stability of V-doped Ti4O7 was also revealed based on density functional theory (DFT) calculations.

In situ crystallization of Fe-Ti oxides in the Bijigou layered intrusion: Insights from crystal size distributions and compositions of magnetite and ilmenite

The formation of Fe-Ti oxide ore bodies in layered intrusions is attributed to in situ crystallization of basaltic magmas or accumulation after crystal settling regardless of their thicknesses and occurrences in the intrusion. These two key processes are difficult to be distinguished in terms of chemical compositions of minerals or cumulates. However, the crystal size distributions (CSDs) of Fe-Ti oxides in the rocks can be remarkably distinct in these two processes. In this study, we collected samples from a drill core profile across the major Fe-Ti oxide-rich segment of the Bijigou intrusion, a large and differentiated layered intrusion in Central China, and carried out a detailed study on the CSDs and in situ major and trace elements of magnetite and ilmenite to examine how Fe-Ti oxides are accumulated to form Fe-Ti oxide ore bodies in the intrusion. The major Fe-Ti oxide-rich segment of the intrusion consists of, from the base upward, a Fe-Ti oxide ore layer (∼80 m), a troctolite unit (∼153 m), an oxide gabbro unit (∼165 m) and an apatite-oxide gabbronorite unit (∼165 m). Large grains of magnetite and ilmenite in the Fe-Ti oxide ore layer show logarithmic-linear CSD curves, similar to those yielded by in situ crystallization of Fe-Ti oxides. The modes of Fe-Ti oxides in the oxide gabbro unit and apatite-oxide gabbronorite unit fluctuate along the profile, which cannot be attributed to accumulation after crystal settling. In addition, the magnetite of the Fe-Ti oxide ore layer, oxide gabbro unit and apatite-oxide gabbronorite unit shows a gentle increase trend of Cr concentration from the base upward in each unit, inconsistent with the trend for an accumulation after crystal settling. The magnetite grains enclosed within silicates have similar compositions to those interstitial to silicates, indicating that they all crystallized from similarly interstitial Fe-rich melt. The in situ crystallization of Fe-Ti oxides is likely triggered by increasing oxygen fugacity due to dissociation of H2O in highly evolved interstitial liquid that was expelled from underlying crystal mush. The crystallization of low-Cr magnetite at the base of each unit is attributed to suppressed eddy currents by dramatic increase of latent heat of crystallization in the magmas at the base. The eddy currents may gradually become efficient toward the top of the magmas due to rapid dissipation of latent heat of crystallization in the magmas, leading to crystallization of high-Cr magnetite by ion diffusion on the top of each unit. This study also demonstrates that analysis of CSDs for Fe-Ti oxides is applicable to examine the accumulation mechanism of Fe-Ti oxide ore bodies in layered intrusions.

Studies on the structure and the magnetic properties of high-entropy spinel oxide (MgMnFeCoNi)Al2O4

The study of high-entropy materials has attracted enormous interest since they could show new functional properties that are not observed in their related parent phases. Here, we report single crystal growth, structure, thermal transport, and magnetic property studies on a novel high-entropy oxide with the spinel structure (MgMnFeCoNi)Al2O4. We have successfully grown high-quality single crystals of this high-entropy oxide using the optical floating zone growth technique for the first time. The sample was confirmed to be a phase pure high-entropy oxide using x-ray diffraction and energy-dispersive spectroscopy. Through magnetization measurements, we found (MgMnFeCoNi)Al2O4 exhibits a cluster spin glass state, though the parent phases show either antiferromagnetic ordering or spin glass states. Furthermore, we also found that (MgMnFeCoNi)Al2O4 has much greater thermal expansion than its CoAl2O4 parent compound using high resolution neutron Larmor diffraction. We further investigated the structure of this high-entropy material via Raman spectroscopy and extended x-ray absorption fine structure spectroscopy (EXAFS) measurements. From Raman spectroscopy measurements, we observed (MgMnFeCoNi)Al2O4 to display a combination of the active Raman modes in its parent compounds with the modes shifted and significantly broadened. This result, together with the varying bond lengths probed by EXAFS, reveals severe local lattice distortions in this high-entropy phase. Additionally, we found a substantial decrease in thermal conductivity and suppression of the low temperature thermal conductivity peak in (MgMnFeCoNi)Al2O4, consistent with the increased lattice defects and strain. These findings advance the understanding of the dependence of thermal expansion and transport on the lattice distortions in high-entropy materials.

Quantum mechanical simulation of polarization switching in HfO2 crystals

The work is devoted to the study of the process of changing the polarization of hafnium oxide crystals in the orthorhombic phase associated with the gradual weakening of the polarization effects in FeRAM elements based on thin films of hafnium oxide HfO2. To solve the problem, quantum-mechanical calculations of the structure of orthorhombic hafnium oxide were carried out, a possible way of crystal rearrangement during a change in polarization upon application of voltage was identified, and its optimization was carried out using the elastic band method. The values of the polarization change and the energy barrier of the corresponding transition are obtained. A study of the stability of this transition has been carried out. The results of a series of computational experiments using high-performance computing systems of hybrid architecture based on the Center for Collective Use of the FRC IU RAS are presented. An analysis of the results shows that, despite the low energy barrier of the transition, the probability of a spontaneous change in polarization is low due to the impossibility of changing the polarization of an individual cell without taking into account the influence of the polarizations of neighboring cells.

Study on the intrinsic defect in [formula omitted] crystal from combined first-principles and thermodynamic calculation

Erbium oxide (Er2O3) crystal is expected to be a new generation of persistent luminescence devices. The intrinsic point defects have a great influence on the properties of crystals. So, we investigated the formation energy of intrinsic point defect in Er2O3 crystal by density functional theory (DFT) and thermodynamic calculation. The effect of vibration entropy variation with temperature is considered. The results show that the influence of vibrational entropy on the formation energy should not be ignored under high-temperature. The defect formation energy under varied temperatures and oxygen partial pressure has been obtained. The results indicate that the most stable defect change from oxygen vacancies to erbium vacancies when the Fermi level increases from valence band maximum (VBM) to conduction band minimum (CBM). Erbium vacancies are predicted as shallow level acceptors. Fermi pinning effect causes the crystal to have a p-type conductive behavior. Our calculated result can provide the optimization condition for adjusting the main defect types to satisfy the needs of application.

A Perspective on the state-of-the-art functionalized 2D materials

Two-dimensional (2D) ultra-thin materials are more crucial than their bulk counterparts for the covalent functionalization of their surface owing to atomic thinness, large surface-to-volume ratio, and high reactivity of surface atoms having unoccupied orbitals. Since the surface of a 2D material is composed of atoms having unoccupied orbitals, covalent functionalization enables one to improve or precisely modify the properties of the ultra-thin materials. Chemical functionalization of 2D materials not only modifies their intrinsic properties but also makes them adapted for nanotechnology applications. Such engineered materials have been used in many different applications with their improved properties. In the present Perspective, we begin with a brief history of functionalization followed by the introduction of functionalized 2D materials. Our Perspective is composed of the following sections: the applications areas of 2D graphene and graphene oxide crystals, transition metal dichalcogenides, and in-plane anisotropic black phosphorus, all of which have been widely used in different nanotechnology applications. Finally, our Perspectives on the future directions of applications of functionalized 2D materials are given. The present Perspective sheds light on the current progress in nanotechnological applications of engineered 2D materials through surface functionalization.

Application of Fe0.66Cu0.33@Al(OH)3 catalyst from fluidized-bed crystallizer by-product for RB5 azo dye treatment using visible light-assisted photo-Fenton technology

This study aims to explore the reusability of wastewater treatment by-product for photo-Fenton process to treat an organic pollutant model. The optimal condition, reactive oxygen species (ROS), and kinetic approach in photo-Fenton process was discussed. The Metal oxide crystal pellets from are a by-product of the Fluidized-Bed Crystallization (FBC) process and can be used as a catalyst in the Photo-Fenton process. Electroplating wastewater containing iron and copper was treated via the FBC process using granulated Al(OH)3 as carrier seeds. The binary oxide of FeOOH and Cu2O on the Al(OH)3 surface (Fe0.66Cu0.33@Al(OH)3) was identified as the FBC by-product after characterization using FTIR and XPS analysis.In the photo-Fenton process, visible light from a fluorescence lamp with a wavelength of 400–610 nm was chosen as an irradiation source. Oxalic acid was added as chelating agent to form photosensitive iron oxalate species and hydrogen peroxide was applied as oxidant to generate active radical to decolorize and mineralize RB5 synthesized solution (100 mg/L). The operating conditions including the oxalic acid to pollutant ratio ([OA]0/[RB5]0) of 4.5–13.0, reaction pH (pHr) of 3–7 and initial to theoretical hydrogen peroxide molar ratio [H2O2]0/[ H2O2]theoretical of 35%–120% were optimized. Under the optimal conditions, pHr = 5.0; [H2O2]0/[RB5]0 at 75% stoichiometric and [OA]0/[RB5]0 = 9, the RB5 is almost completely decolorized after 210 min of operation and the mineralization efficiency is 58%. The contribution of •OH, O2•-, and O21 to the Photo-Fenton system was determined using ESR analysis with the addition of DMPO and TEMP as spin trap agents. The kinetic analysis reveals the observed rate constants kRB5, kOA and kR from fitting are 0.0120, 0.0054 and 0.0001 M−1s−1, respectively.

Sub-nanometer scale depth patterning on sapphire crystal by femtosecond soft x-ray laser pulse irradiation.

Damage thresholds and structures on a metal aluminum and an aluminum oxide crystal induced by the soft x-ray free electron laser irradiations were evaluated. Distinctive differences in damage thresholds and structures were observed for these materials. On the aluminum oxide crystal surface, in particular, a novel, to the best of our knowledge, surface processing, which we suggest defining as "peeling," was recognized. Surface structures formed by peeling had extremely shallow patterning of sub-nanometer depth. For the newly observed peeling process, we proposed a scission of chemical bond, i.e., binding energy model, in the crystal.

Mechanistic understanding of the localized corrosion behavior of laser powder bed fused 316L stainless steel in pressurized water reactor primary water

The laser powder bed fused (LPBFed) stainless steels showed anomalous and localized corrosion behavior in the nuclear reactor high-temperature water compared to their wrought counterparts, which affects their performance during plant operation. In this study, advanced microstructural characterization was performed on LPBFed 316 L sample along with wrought 316 L sample after corrosion tests to understand the underlying mechanisms. The results showed that an inhomogeneous/discontinuous inner oxide layer formed on LPBFed 316 L, in contrast to the continuous inner oxide layer on the wrought 316 L specimen. This discontinuous inner oxide layer was identified to consist of Cr-enriched nano-sized spinel oxide and the barrier layer features a Ni-enriched hexagonal close-packed Laves phase. Localized/preferential oxidation was found to occur along the cellular walls which were tangled with high density dislocations and decorated with Mn and Si-enriched nano-sized precipitates, and the nano-precipitates were observed in the core of dispersed Cr-enriched inner oxide crystals.

On the successful growth of bulk gallium oxide crystals by the EFG (Stepanov) method

Bulk crystals of [Formula: see text]-Ga2O3 were successfully grown by the EFG (Stepanov) method. Analysis of the material using an X-ray diffraction showed the high crystalline quality of the obtained crystals. However, when determining the elemental composition by the Energy Dispersive X-ray Spectroscopy (EDS) method, a deviation of the crystal composition from a stoichiometric one was found and a lack of oxygen was detected. Indirectly, this indicates the non-optimal composition of the atmosphere in the growth zone. The origin of this deviation of the composition can be oxygen vacancies in the bulk of the crystal. However, the absorption spectrum does not contain peaks characteristic for oxygen vacancies in gallium oxide. An analysis of the optical transmission spectra made it possible to estimate the optical bandgap of the grown gallium oxide samples, which was 4.7 eV.

In situ observation of two-step crystallization of amorphous oxides via electron microscopy

The transformation from amorphous materials to crystals and the corresponding microscopic mechanism have become a research focus in materials science, condensed matter physics, and biophysics etc. In this paper, taking Y3Al5O12 (YAG) as an example, the crystallization process of amorphous YAG oxide is investigated from an atomic point of view through the combination of spherical aberration-corrected transmission electron microscopy (SCTEM) with an in situ heating method, and the morphology and structural evolution of the surface and interface are explored. It is observed that the crystallization proceeds on the surface and interior of the amorphous YAG separately. Through atomic-scale imaging, it is determined that semi-ordered structures are formed in a few atomic layers at the amorphous/crystalline interface and that the structural transformation process from the amorphous to the semi-ordered state and then to the crystal structure may be the main reason for the multiple stages of the crystallization of amorphous oxides. This study demonstrates the mechanism of the amorphous-to-crystal transformation on the atomic scale and contributes to gaining a better understanding of the crystallization process of bulk oxides, especially complex metal oxides.

Alleviating the Crystallization Dynamics and Suppressing the Oxidation Process for Tin‐Based Perovskite Solar Cells with Fill Factors Exceeding 80 Percent

AbstractThe low toxicity and a near‐ideal bandgap endow tin (Sn)‐based perovskite solar cells (TPSCs) a promising future in photovoltaic technologies. However, in general the Sn‐based perovskites suffer from poor resistance to oxidation and fast crystallization dynamics, resulting in low fill factors (FFs) and power conversion efficiencies (PCEs). Herein, a strategy to improve the performance of TPSCs by incorporating 2‐(2‐aminoethyl)–2‐thiopseudourea dihydrobromide (AET) into the Sn‐based perovskites is proposed. AET interacts strongly with the Sn‐based perovskites, and thus effectively inhibits the oxidation from Sn2+ to Sn4+ and slows down the crystallization process. As a result, the TPSCs with AET achieve a high FF of 80.26% and a high PCE of 13.55%. Notably, this FF value represents the highest reported in the field of TPSCs with narrow bandgaps. Furthermore, encapsulated TPSCs demonstrate good stability, maintaining 80% of their initial performance over the course of 700 h.

Impact of Hard Magnetic Nanocrystals on the Properties of Hardened Cement Paste

AbstractIn this work, nano‐sized hard magnetic gallium‐substituted iron oxide crystals, wherein gallium is used to stabilize the metastable epsilon iron oxide phase, were added to cement‐water suspensions at different ratios, which were subsequently hydrated for at least 28 days. It is shown that higher contents of such nanocrystals in the hardened cement paste introduce a magnetic moment, whereas the mechanical properties remain unchanged compared to non‐blended hardened cement paste for a wide concentration range.

Multi‐Analyte Sensitive Fluorophore Cross‐Linked Nanofibers Based Antimicrobial Surface Enabling Bacterial Detection and Their Usage as Crystal Growth Template

AbstractIn situ preparation of bifunctional thiazolo[5,4‐d]thiazole (TTz)‐based fluorophore cross‐linked nanofibers is successfully performed. These multifunctional nanofibers are used as both crystal growth template and antibacterial substrate that makes bacterial detection possible simultaneously. These highly fluorescent nanofibers act as optical sensors toward many analytes. The acid, base, and metal cation‐sensitive nature of the 2,5‐bis(4‐hydroxyphenyl)thiazolo[5,4‐d]thiazole (HPhTT) dye makes the prepared PVA nanofibers sensitive against these chemicals. Metal nanoparticles (MNPs) or metal oxide crystal formation occurs on the surface of nanofibers without any reducing agent. The strong interaction between metal cations and fluorophores results in crystal formation on the surface, which is named for the first time as “complexation‐triggered crystalization.” These dye cross‐linked and metal‐interacted nanofibers exhibit antibacterial effect against E. coli (ATCC 25922), S. aureus (ATCC 25923), P. aeruginosa (ATCC 27853), and E. faecalis (ATCC 25922) strains. Also, the emission wavelength change of nanofibers in bacterial contamination makes it possible to use smart nanofiber films for optical bacteria detection. These novel materials pave the way for new applications such as smart wound bands, optical sensors, and one‐step preparation of surface‐enhanced Raman spectroscopy substrate.

Synthesis and Characterization of Silicon–Carbon Powder and Its Resistance to Electron Irradiation

The issue of crystallization of silicon oxide at low temperatures is a topical issue for the electronics of the future. Organosilicon oligomers and polymers are “ideal” sources for obtaining ultrapure silicon ceramics and silicon nanoparticles. This paper presents the results of the synthesis of highly dispersed silicon-carbon powder from an organohydrosiloxane oligomer and the method for increasing its crystallinity at low temperatures. The diffraction pattern of the resulting powder corresponds to the amorphous–crystalline state of the components in this material, as evidenced by two intense and broadened amorphous halos in the region of Bragg angles 2θ = 7–11° and 18–25°. The resulting silicon–carbon powder was subjected to electron irradiation (E = 10 MeV; D = 106–107 Gy). This paper presents the data on the changes in powder properties via IR-Fourier spectroscopy, X-ray phase analysis, and scanning electron microscopy. Irradiation with fast electrons with an absorbed dose of 106 Gy leads to a slight crystallization of the amorphous SiO2 phase. An increase in the absorbed dose of fast electrons from D = 106 to D = 107 Gy leads to the opposite effect. An amorphization of silica is observed. This study showed the possibility of the crystallization of a silicon–carbon powder without a significant increase in temperature, acting only with electron irradiation. It is necessary to continue further research on expanding the boundaries of the optimal doses of absorbed radiation from fast electrons in order to achieve the maximum effect of the crystallization of silicon–carbon powder.