Fresh Film Research Articles

Novel Strategy for High Efficient and Stable Perovskite Solar Cells through Atomic Layer Deposition.

The perovskite material has demonstrated conceivable potential as an absorbing material of solar cells. Although the power conversion efficiency of the device based on perovskite has rapidly come to 26%, there are still many factors that affect the further improvement of the photoelectric conversion efficiency. Interface defects are the dominating concern that influence carrier transportation and stability. Here, we report a novel strategy where B2O3 is deposited on the fresh perovskite film by atomic layer deposition technology. The organic atmosphere during atomic layer deposition can effectively regulate the crystallization kinetics of perovskites and promote crystal growth. The B2O3 adsorbed on the perovskite light-absorption layer can effectively reduce the electropositive defects on the surface of the perovskite, such as uncoordinated Pb2+ and I vacancies due to the electron-donating properties of the side O atoms in B2O3. Consequently, the power conversion efficiency of the perovskite solar cell after B2O3 treatment increases to 21.78% from 18.89%. Simultaneously, B2O3 can improve the stability of devices.

Analytical Variability and Agreement of Leukocyte Quantification Methods in Inland Bearded Dragons (Pogona vitticeps)

Abstract Hematology is a common diagnostic assay for evaluation of health in veterinary species. Several manual methods exist to evaluate the leukocyte component of reptile complete blood counts; however, there is no single method that has been proven reliable for all reptiles. To investigate the analytical variability and agreement of commonly used leukocyte quantification methods, blood was collected from ten clinically healthy bearded dragons (Pogona vitticeps) and analyzed in triplicate using Natt-Herricks (NH), eosinophilic leukopet (LO), and estimated white blood cell counts on peripheral blood smears made from fresh whole blood or blood anticoagulated with lithium heparin (LH). To investigate inter-observer variability, blood film white blood cell estimates were generated by both a novice veterinary student and a boarded clinical pathologist and analyzed for agreement. Analytical variability was highest using the LH blood film estimate by a boarded clinical pathologist (21.0%), followed by Natt-Herricks method (student) (20.8%), fresh whole blood film estimate from the clinical pathologist (16.6%), eosinophilic leukopet (student) (8.7%), and blood film estimates using fresh whole blood (6.5%) and LH blood (4.5%) read by the student. Bland Altman plots revealed there was agreement between LO and NH methods and between the two blood film estimate methods, and Passing-Bablok regression analysis revealed constant and proportional error between LO and both estimate methods and between NH and both estimate methods. There was agreement between the veterinary student and clinical pathologist for both blood smear leukocyte estimates. These results highlight the importance of considering which leukocyte quantification method is used when clinically assessing reptile patients.

FirstReportofFusariumsolaniassociatedwithTwigCankerofEnglishWalnut(JuglansregiaL.)inXinjiang, China.

English walnut (Juglans regia L.) is a perennial deciduous fruit tree, and an economically important hardwood tree species cultivated worldwide. As one of the important economic crops, English walnut is also widely cultivated in Xinjiang. In September 2019, twig canker symptoms were observed on English walnut in several orchards, with approximately 15% to 40% disease incidence in southern Xinjiang region (79º95'E, 40º37'N). The branch lesions were long oval, concave, and black to brown. Leaves of the affected branches turned yellow and the branches eventually died. Infected twigs were collected from an infected tree in an orchard. Symptomatic tissue from the margins of cankers was surface disinfested with 75% ethanol for 60 s, rinsed 3 times with sterile water, and then incubated on potato dextrose agar medium (PDA) at 25 ℃ under a 12-hr photoperiod in Light incubator for 7 days. Seven fungal isolates showing similar morphology were obtained from the symptomatic tissue. All the fungal cultures had a pink-white color with loose, cottony mycelium, and the underside of the colonies were light brown. Macroconidia were slightly curved, with one to six septa, both ends were slightly sharp, and they measured 22.8 to 38.5 × 3.5 to 6.7 μm (27.4 ± 0.6 × 4.2 ± 0.3 μm, n=50). Microconidia were oval, hyaline, zero to one septa, measuring 4.5 to 9.6 × 1.8 to 2.3 μm (6.8 ± 0.3 × 2.1 ± 0.1 μm, n=50). According to the morphological characteristics, the seven isolates were identified as a member of the Fusarium solani species complex (Summerell et al. 2003). Genomic DNA was extracted from the representative isolate HSANTUAN2019-1, and the internal transcribed spacer (ITS) region, the translation elongation factor 1-alpha (TEF) were amplified with the primer pairs ITS1/ITS4 (White et al. 1990) and EF1-F/EF2-R (O' Donnell et al. 2010), respectively. The sequences submitted to GenBank (accession nos. OP271472 for ITS, OP293104 for TEF) showed high similarity with the reference sequences of F. solani (ITS, OL691083 [100%]; TEF, HE647960 [99.86%]). Pathogenicity of the seven isolates were assessed on 1-year-old branches of English walnut in the field. Healthy branches (40) were wounded with a sterilized hole punch, and then inoculated with isodiametric mycelial PDA plugs (5 branches per fungal isolate). Five branches were inoculated with sterile PDA plugs as a negative control. The inoculations were performed three times. All treatments were wrapped with fresh film for 3 days. Dark brown necrotic lesions were observed on all inoculated branches 22 days post-inoculation. The controls had no symptoms. The pathogen was reisolated from all the inoculated branches, fulfilling Koch's postulates. To our knowledge, this is the first report of F. solani causing twig canker on English walnut in Xinjiang, China. Twig canker disease often cause a large number of branches to dry out and die. If the disease control and prevention is neglected, the productivity of the English walnut will be seriously affected in the cultivation area. Our finding will provide valuable information for prevention and management of twig canker on English walnut.

Dynamically stable and amplified circularly polarized excimer emission regulated by solvation of chiral co-assembly process

Chiral supramolecular assembly has been assigned to be one of the most favorable strategies for the development of excellent circularly polarized luminescent (CPL)-active materials. Herein, we report our study of an achiral boron-containing pyrene (Py)-based chromophore (PyBO) as a circularly polarized excimer emission (CPEE) dye induced by chiral co-assemblies containing chiral binaphthyl-based enantiomers (R/S-M). Chiral co-assembly R/S-M-(PyBO)4 fresh film spin-coated from toluene solution can exhibit orderly nanofibers and strong green CPEE (λem = 512 nm, gem = ±0.45, ΦFL = 51.2 %) resulting from an achiral PyBO excimer. In contrast, only a very weak blue CPL was observed (λem = 461 nm, gem = ± 0.0125, ΦFL = 19.0 %) after 187 h due to PyBO monomer emission as spherulite growth. Interestingly, this kind of chiral co-assembly R-M-(PyBO)4-T film from tetrahydrofuran (THF) solution retains uniform morphology and affords the most stable and strongest CPEE performance (λem = 512 nm, gem = + 0.62, ΦFL = 53.3 %) after 10 days.

Mitigating deep-level defects through a self-healing process for highly efficient wide-bandgap inorganic CsPbI3−xBrx perovskite photovoltaics

Thermal admittance spectroscopy is used to explain the self-healing process in the wide bandgap inorganic CsPbI3−xBrx. It is revealed that the deep-level interstitial defects in the fresh film can be self-healed when stored in a low-humidity ambient condition.

Zinc influence on nanostructured tin oxide (SnO2) films as ammonia sensor at room temperature

We report the fabrication of Zn defect-influenced SnO2 sensor operating at room temperature. The films for the sensor were prepared by automatic nebulizer spray pyrolysis under a no-vacuum environment. Four different films were prepared with different Zn doping concentrations; 0 at.%, 1 at.% 3 at.% and 5 at.%. The X-ray diffraction analysis showed a tetragonal rutile structure with polycrystalline behavior for all films. The crystallinity was suppressed by Zn doping due to the influence of extrinsic donor defects. When increasing the Zn doping level, the bandgap is increased owing to the observed blue shift in the optical transmittance. The photoluminescence (PL) spectra of films show a UV emission at 361 nm which reveals near band edge (NBE) emission. And also, the intensity of the NBE emission decreases with an increase in Zn content due to the creation of defect states near the conduction band. The green emission intensity starts to increase with Zn doping indicates the excess oxygen vacancies (Vo) and/or oxygen interstitials in the host structure. These defects play a major role in controlling the interaction between the sensor surface and ammonia (NH3) molecules. NH3 gas sensing studies were carried out at room temperature for all the prepared films. A maximum sensitivity of 121% was exhibited by SnO2 sensor prepared by 3 at.% substitution of Zn. The maximum sensitivity is attributed to the presence of increased defects on the film surface. In addition, Zn doped SnO2 sensors exhibited fast response and recovery times when compared with the undoped sensor. The optimum sensor (3 at.% of Zn) exhibited good repeatability and reproducibility of sensor performance. The aging effect on the sensing behavior showed the maintenance of stability above 90% for the aged film (100 days) when compared with the fresh film.

The Significant Effect of Carbon and Oxygen Contaminants at Pd/p‐GaN Interface on Its Ohmic Contact Characteristics

A low‐resistance Ohmic contact of Pd/Pt/Au metallization scheme is formed on a p‐type GaN film grown by metal‐organic chemical vapor deposition (MOCVD). Two samples are prepared to explore the effect of contaminations at the metal and GaN interface on the properties of the Ohmic contact. One directly transfers the fresh GaN film from MOCVD to the metal deposition chamber through an ultrahigh vacuum (UHV) tube, without exposing the GaN surface to air; the other transfers the GaN film from MOCVD to metal deposition through the atmosphere. The results show a lower specific contact resistance (6.2 ± 0.9) × 10−5 Ω cm2 for the directly UHV‐transferred sample than the air‐transferred sample (2.1 ± 0.9) × 10−4 Ω cm2. Once exposed to air, carbonaceous particles and an amorphous oxide layer easily adhere to the p‐type GaN surface, which not only increase the Schottky barrier height but also generate more grain boundaries in the Pd/Pt/Au stacks. The grain boundaries, acting as diffusion channels, make Au atoms diffuse easily into the Pd layer and propagate to the p‐GaN surface layer after annealing. Therefore, the Ohmic contact fabricated in UHV ambience with lower oxygen and carbon contaminations at the interface shows superior characteristics than the samples prepared by the traditional method.

Temperature and frequency dependence of AC electrical conductivity, dielectric permittivities, modulus and impedance parts for thermally deposited Se80S20 thin film

In this framework, the bulk sample of Se80S20 has been successfully generated using the common melt quenching method. The main structural characteristics of Se80S20 were checked utilizing EDAX, X-ray, and SEM measurements. The thin film (~500 nm) fabricated from the bulk sample is thermally deposited on a clean glass substrate at 298 K using the evaporation technique. The thickness of the analyzed film has been monitored by a crystal monitor. On the other hand, the dielectric permittivities, dissipation factor, AC electrical conductivity, modulus, and impedance components were determined based on the capacitance-temperature (Cm-T), capacitance-frequency (Cm-ω), conductance-temperature (Gm-T), and conductance-frequency (Gm -ω) measurements. AC electrical conductivity, σAC(T) has two contributes, electronic and ionic conductivity. Physical parameters of Se and S elements have been reported. As well, the important electrical parameters such as the power of angular frequency m, the maximum barrier height Wm, energy band gap Eg, the pre-exponential factor σο, the activation energy of the conduction mechanism, EAC in both extended and hopping regions and the relaxation parameters of fresh Se80S20 thin film at different frequencies have been computed. Finally, the behavior of the local state density at the Fermi level has been studied as a function of temperature at different frequencies and also as a function of frequency at different temperatures.

Comparative study of thermochromic properties on fresh and aged vanadium dioxide films

Vanadium dioxide (VO2) thin films were fabricated by means of DC reactive magnetron sputtering at low temperature, and then were aged in air for 5 years. The thermochromic properties of the fresh VO2 film and aged one were investigated by UV–visible spectrophotometer. The experimental results show that the fresh VO2 film shows excellent thermochromic properties with a high visible transmittance of 40.8% and a large switching efficiency of 73% at 2500 nm. For the film aged in ambient air for 5 years, the visible transmittance is increased to 54.0% due to a blue-shift of absorption edge and a decrease in luminous absorbance. More interestingly, the aged VO2 film still keeps a relatively large switching efficiency of 51% at 2500 nm, suggesting the deposited VO2 film has a good thermochromic stability in ambient air. These characteristics indicate the practical applications of VO2 film to smart optical devices.

Time-resolved measurement of space-charge evolution in dielectric films or slabs by means of repeatable laser-induced pressure pulses.

A new variant of the Laser-Induced Pressure-Pulse (LIPP) method for repeatable, time-resolved space-charge profile measurements is proposed and demonstrated. Automated deposition of a fresh laser-target film before each illumination leads to good repeatability of the LIPP and thus allows for the detection of time-resolved changes in the space-charge distribution over many hours. We describe and discuss the experimental setup and its features, compare the repeatability of the LIPP measurements on the same sample without and with re-preparation of the test cell, and present the time-resolved evolution of the space-charge profile in a two-layer arrangement of a silicone-grease and a silicone-elastomer film as an example. Finally, the temperature dependence of the space-charge evolution during polarization under high voltage and during depolarization in short circuit is shown. Possible uses and future developments of the new LIPP approach are also discussed.

Investigation of ultraviolet radiation aging gradient in asphalt binder

The phenomenon of ultraviolet (UV) radiation aging gradient in asphalt binder is existent but usually neglected in most of UV radiation aging simulations and real asphalt pavement. Therefore, it is necessary to investigate the developing velocity and causing mechanism of UV aging gradient in asphalt binder. In this paper, the 3 mm-thickness asphalt films that suffered different UV radiation aging periods were divided into average three layers by peeling procedures. Then, rheological properties, molecular sizes distributions, chemical functional groups contents and fluorescence tests were conducted on different asphalt layers. The results indicate that by rheological indexes, the effect of 6-day UV aging is almost negligible, but the UV aging depth can exceed 1 mm after 9-day UV aging period and further exceed 2 mm after 15-day UV aging period. In addition, the vertical gradients of molecular sizes and oxidation products contents tend to form in asphalt film as UV aging process proceeds. Moreover, the observation of inorganic fluorescent powders being able to permeate into fresh asphalt film in lower layers by fluorescence microscope objectively demonstrates the “diffusion aging model” ─ UV aged asphalt molecules diffuse downwards into fresh asphalt film in lower layer.

Characterization and identification of lacquer films from the Qin and Han dynasties

A comprehensive investigation was undertaken of red–black lacquer films excavated from a tomb in the Qin and Han Dynasty period (221 BC to AD 8). Cross-sectional observation was conducted via metallomicroscopy and field-emission scanning electron microscopy (FE-SEM). Morphological characteristics were investigated via FE-SEM with energy dispersive X-ray spectrometry (EDX). X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were also conducted. The results of the cross-sectional analysis showed that the finished lacquer films on the wood body included a ground layer with coarse materials and a lacquer layer with delicate materials. Both SEM and EDX indicated that carbon black was used as the main black pigment, and cinnabar was used as the main red pigment. Compared with the standard card test, the XRD patterns of the Chinese lacquer were similar to that of quartz (SiO2), indicating that SiO2 was used as a putty powder during lacquer finishing. Compared with the FTIR spectrum of the fresh lacquer film, only a small amount of free carbonyl was found in the degraded lacquer, and some organosilicates were likely generated during degradation spanning thousands of years.

Elaboration and Characterization of Active Films Containing Iron-Montmorillonite Nanocomposites for O2 Scavenging.

Iron particles of sizes between 6 and 20 nm forming aggregates of 57 ± 17 nm were synthesized by chemical reduction of iron precursors on the surface of montmorillonite (MMT). This active MMT-Fe powder was then uniformly distributed in a linear low-density polyethylene (LLDPE) matrix by extrusion at atmospheric conditions, as confirmed by wide-angle X-ray scattering (WAXS), which also detected a partial exfoliation of the nanoclays. Thermogravimetric analysis (TGA) did not detect any significant modification of the degradation temperature between nanocomposites and active nanocomposites. 57Fe Mössbauer spectroscopy evidenced the formation of a majority of iron boride in MMT-Fe as well as in the active film containing it. The LLDPE.Fu15.MMT-Fe3.75 and LLDPE.Fu15.MMT-Fe6.25 films had oxygen-scavenging capacities of 0.031 ± 0.002 and 0.055 ± 0.009 g(O2)/g(Fe), respectively, while the neat powder had an adsorption capacity of 0.122 g(O2)/g(Fe). This result confirms that the fresh film samples were partially oxidized shortly after thermomechanical processing (60% of oxidized species according to Mössbauer spectroscopy). No significant difference in oxygen permeability was observed when MMT-Fe was added. This was related to the relatively small film surface used for measuring the permeability. The reaction–diffusion model proposed here was able to reproduce the observed data of O2 adsorption in an active nanocomposite, which validated the O2 adsorption model previously developed for dried MMT-Fe powder.

Zirconium oxynitride films: Modulation of component as a function of the preparation parameters

Zirconium oxynitride films have recently received much attention because their properties may gradually be changed by varying the concentration of N, O and Zr constituents during processing. Here, we reported zirconium oxynitride films prepared by RF reactive magnetron sputtering technique. The films were deposited by different targets: ZrO2 and ZrN with the variation of nitrogen and oxygen flow rate. To explore whether the N content could be gradually incorporated into the films, two series of samples were prepared: one was prepared by the ZrO2 target with the variation of the nitrogen flow rate; the other was prepared by the ZrN target with the variation of the oxygen flow rate. The composition and structure of the films were investigated by XPS, EDS and XRD techniques. XPS results show that when the ZrO2 material was used as target the concentration of N was highly dependent on the flow rate of nitrogen, while the Zr concentration gradually decreased with the increase of N concentration; ZrO[Formula: see text]N[Formula: see text] and ZrO were formed. However, for ZrN used as target, the fresh film of the sample comprised of O and Zr elements without N detected. When the N2 was introduced as reactive gas with oxidized ZrN target, ZrO[Formula: see text]N[Formula: see text] film with a certain content of N was formed.

Ultrasensitive Heterojunctions of Graphene and 2D Perovskites Reveal Spontaneous Iodide Loss

Summary Despite the demonstrated high efficiency of perovskite solar cells and light-emitting devices, the understanding of the intrinsic stability of perovskites is far from complete. In this work, using an ultrasensitive, exfoliated 2D perovskite single-crystal sheet/graphene heterostructure device, we reveal spontaneous iodide loss as an important degradation pathway of 2D perovskite single crystals, which n-dopes the perovskite semiconductor by generating positively charged iodide vacancies. Furthermore, we show that covering perovskites with graphene can suppress the iodide loss, significantly improving perovskite stability. A perovskite phototransistor is demonstrated with a graphene/2D perovskite/graphene structure, which shows no degradation after 75 days. Our work not only provides important insights for future stable perovskite optoelectronic device development, but also demonstrates the potential of graphene as a promising sensitive diagnostic tool for device and material degradation studies.

Reduced-Dimensional α-CsPbX3 Perovskites for Efficient and Stable Photovoltaics

Summary Inorganic CsPbX3 perovskites have gained great attention owing to their excellent thermal stability and carrier transport properties. However, the power conversion efficiency (PCE) of solution-processed CsPbX3 perovskite solar cells is still far inferior to that of their hybrid analogues. Insufficient film thickness and undesirable phase transition are the two major obstacles limiting their device performance. Here, we show that by adopting a new precursor pair, cesium acetate (CsAc) and hydrogen lead trihalide (HPbX3), we were able to overcome the notorious solubility limitation for Cs precursors to fabricate high-quality CsPbX3 perovskite films with large film thickness (∼500 nm). We further introduced a judicious amount of phenylethylammonium iodide (PEAI) into the system to induce reduced-dimensional perovskite formation. Unprecedentedly, the resulting quasi-2D perovskites significantly suppressed undesirable phase transition and thus reduced the film's trap density. Following this approach, we reported a state-of-the-art PCE to date, 12.4%, for reduced-dimensional α-CsPbI3 perovskite photovoltaics with greatly improved performance longevity.

Morphology modification of electrodeposited superhydrophobic nickel coating for enhanced corrosion performance studied by AFM, SEM-EDS and electrochemical measurements

In this work, an electrodeposited superhydrophobic nickel film with apparent contact angle of 156° was fabricated using different contents of H3BO3 as a morphological modifier to effectively improve the corrosion resistance of the underlying copper substrate. Atomic force microscopy and scanning electron microscopy analysis allowed visualization of growth mechanism and morphology of the electrodeposited coating in the presence and absence of H3BO3. The results showed that H3BO3 considerably effects on morphology of coating by its hindering property that leads to form micro and micro-nanocones hierarchical structures with the mechanism of screw dislocation-driven growth. The spontaneous adsorption of airborne hydrocarbon contaminants on the nickel micro-nanostructures enhances the hydrophobicity of the surface. Cyclic voltammetry and X-ray diffraction provide other evidences of the boric acid hindering effect. The quantitative analysis of atomic force microscopy results showed that after about 5 months exposure to air, the roughness value has been decreased and apparent contact angle has been decreased to 127°. Finally, corrosion behavior of the superhydrophobic nickel film was investigated in 3.5 wt.% NaCl by means of AC/DC electrochemical methods. Regarding potentiodynamic polarization and electrochemical impedance spectroscopy, the superhydrophobic nickel film (Cassie-Baxter state) exhibited five times greater corrosion resistance in comparison with fresh nickel film (Wenzel state).

Design and Synthesis of Polyimides Based on Carbocyclic Pseudo-Tröger’s Base-Derived Dianhydrides for Membrane Gas Separation Applications

Two novel carbocyclic pseudo-Troger’s base-derived dianhydrides, 5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene-2,3,8,9-tetracarboxylic anhydride (CTB1) and its dione-substituted analogue 6,12-dioxo-5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene-2,3,8,9-tetracarboxylic dianhydride (CTB2), were made and used for the synthesis of soluble polyimides of intrinsic microporosity with 3,3′-dimethylnaphthidine (DMN). The polyimides CTB1-DMN and CTB2-DMN exhibited excellent thermal stability of ∼500 °C and high BET surface areas of 580 and 469 m2 g–1, respectively. A freshly made dione-substituted CTB2-DMN membrane demonstrated promising gas separation performance with O2 permeability of 206 barrer and O2/N2 selectivity of 5.2. A higher O2 permeability of 320 barrer and lower O2/N2 selectivity of 4.2 were observed for a fresh CTB1-DMN film due to its higher surface area and less tightly packed structure as indicated by weaker charge-transfer complex interactions. Physical aging over 60 days res...

Comparative study on dielectric behavior in fresh and aged Na0.5Bi0.5(Ti,Fe,W)O3 thin films

Na0.5Bi0.5(Ti0.90Fe0.02W0.08)O3 (NBTFW) thin film was deposited on the ITO/glass substrate by chemical solution deposition. Microstructure, insulating and dielectric performances were measured and compared in fresh and aged samples. Both samples crystallize into phase-pure perovskite structures and possess smooth surfaces without any cracks. Lower leakage current density and relative dielectric constant can be obtained in aged NBTFW film compared to those for fresh one. At low voltage or high frequency, the fresh film exhibits a typical butterfly pattern of normalized dielectric constant–electric field curve, while the aged film shows an abnormal characteristic with two normal double–peaks shape. The related aging mechanism is discussed to be associated with the realignment of VO⋅⋅−FeTi′ defect dipoles along the spontaneous polarization via the migration of mobile oxygen vacancies.

Study of α-Fe2O3 formation and its measurement in oxide films of wheel surface during ELID grinding process

This paper presents the study of forming mechanism of [Formula: see text]-Fe2O3 in oxide films on electrolytic in-process dressing (ELID) grinding wheel surface. To investigate the component content and the microtopography of oxide films, XRD, XPS, IR spectrum analysis, SEM, and TEM measurements are performed on ELID grinding wheels. In XRD test results, the characteristic absorption band of [Formula: see text]-Fe2O3 is found in the oxide film. XPS tests show that there is full of ferrous iron and oxygen element in the oxide film. Also, the characteristic spectral line of XPS is identical to the standard spectrum of [Formula: see text]-Fe2O3. Several vibration peaks (471, 1029, 1384, 1630, 3430) are observed by IR spectrum analysis. It can be easily seen by contrast with the standard photographs that the vibration peak of 1029 is of Fe-O vibration band in IR spectrum of [Formula: see text]-Fe2O3 powder. Therefore, these measurement results confirm the existence of [Formula: see text]-Fe2O3 in the oxide films, and explain the polishing effect of oxide films during ELID grinding. The fresh oxide film is porous and moisture rich. However, the oxide film after squeezing to dry is investigated by SEM imaging to present tortoiseshell cracks. Geometrically, [Formula: see text]-Fe2O3 appears to be nearly spherical with particle size around 5–50 nm. This indicates fine polishing improvement by oxide films, and is identified as the mechanism responsible for excellent surface quality by ELID grinding.